where i can get this schem?
no fet emulation and others please
thanks in advance
Is this what you're looking for? If not, you might want to provide some more info. I'm just taking a guess based on the "Marshall 30 watt transistor".
5010 Master Lead, 30W 1x12" combo (http://www.drtube.com/schematics/marshall/5010.gif)
5203, 30W 1x12" combo (http://www.drtube.com/schematics/marshall/5203.gif)
5010 Thanks!
I have most of the parts to build one of these but can't find any info on the transformer. Does anyone know what voltage it uses? I realise that there will be a +, earth and -ve and need to source a tranformer that will deliver the correct voltage and amps.
Col
QuoteI have most of the parts to build one of these but can't find any info on the transformer. Does anyone know what voltage it uses? I realise that there will be a +, earth and -ve and need to source a tranformer that will deliver the correct voltage and amps.
I can get you into the ball park.
The thing purportedly makes 30W into a single speaker, which is 4 ohms. To get 30W into 4 ohms, we calculate: power P = v^2/R, so P*R = V^2, or V = SQRT(P*r). Then V = SQT(30*4) = 10.95. That's the RMS voltage on the speaker. We need to know peak to get at the power supply. Vpeak = Vrms*1.414, or Vpeak = 15.5V. Add to that a volt for output transistor saturation, and you get 16.5V peak. That peak is either way, so it's +/- 16.5V. This seems to be reasonable, as the preamp uses a 1458 opamp, which can work with up to +/- 18Vdc without dying, and there are no regulators in the circuit to drop voltage to the 1458, only R23 and R24, 2.7K, which would drop off a volt or two.
So you need +/-16.5Vdc. The rectifiers eat up a diode drop on each side; you need 17V peak on each side of the transformer output. That's 17/1.414 = 12Vrms on each half of the transformer, or 24Vac center tapped. Kewl - even a standard value!
As to current, it will need to do 30W reasonably continuously. The efficiency of an AB circuit is about 78.6%. so we're sending 30W to the load and that means we need DC power of 30W/0.786 = 38W from our +/-16.5V supply. The average current is then 38W/33V = 1.15A.
To figure transformer RMS current, the RMS current supplied by a transformer into a capacitor filter in the full wave bridge is about 1.6 to 1.8 times the average. That's 1.84 to 2.07A.
So you need a 24V centertapped secondary, which is rated at 2A. An you're in major luck, as that's a very standard value.
Why would you build this one? ???
What's so good about a naked opamp clipping SS amp? This is no better than a 100$ practice amp.
I thought about this as I already have most of the parts and I have never built an amp before other than a Ruby. I did a layout for the pre-amp and tone shaping section on stripboard and just wanted to try it. I don't think it would get much use as I always use my Laney valve heads for gigs and I already have a 30w combo for home use. If you have any better suggestions for something that can be manufactured from easily available parts between 30 and 60w that would be cool. I have seen the schematic for a 65w power amp using an IC which I have one of but can't remember the number. I must build it sometime and try it.
TDAxxxx... and LM38xxxx... IC's are very nice though. You know little brother LM386 allready, yet it has a big family. Power sections in IC's are far more easy to deal with. I agree that a preamp like this one can be useful, yet I doubt the complexity is that needed.
Remember that on the road from Tubes to FET's to diodes to IC's to transistors the complexity rises getting a good tone.
nekro nekro nekro bump...
RG was close, it needs a 28v center tapped transformer, 1 amp, like the hammond 166j28. it will fit the mounting holes, but this is the stock replacement for these suckahs!
QuoteRG was close, it needs a 28v center tapped transformer, 1 amp, like the hammond 166j28. it will fit the mounting holes, but this is the stock replacement for these suckahs!
If you measure a transformer with no load the voltage will the higher than the rated voltage, somewhere around 10% to 13% for 50VA but it is higher than that smaller tx's and lower for larger tx's. The rated voltage is at full load.
The regulation is (as used by many manufacturers these days),
24V tx: reg% = 100% * (28 - 24)/28 = 14%
25V tx: reg% = 100% *(28 - 25)/28 = 11%
A 30Wamp might use a 60VA transformer (skimped say 45VA).
So the "rated" voltage could well be 24V to 25V.
yeah, i been restoring and repairing these for folks. the 12 watt, 30 watt all are basically the same amp, other than minor changes in the power supply. the hammond is a good replacement, and fits great. aesthetically ya want it to fit the holes usually ;)
and its easier to just KNOW a good part number when you're searching ;)
edit: it matches the original voltages in the original transformers, as i have several of these in my collection in various versions. that's why i said 28v, i think it even specs that on some of the schematics.
believe it or not, the main dif between the 12,20 and 30 watt models is the speaker impedance. 12 @ 16r, 20 @8r, 30 @ 4r
Quote from: pinkjimiphoton on March 02, 2022, 08:45:00 PM
RG was close, it needs a 28v center tapped transformer, 1 amp, like the hammond 166j28. it will fit the mounting holes, but this is the stock replacement for these suckahs!
The transformer in those amps appears to be on the edge as I've see number of posts regarding dead transformers.
That Hammond model you suggested could be somewhat better than the original. The specs for that transformer (and many other Hammond transformers) quote"
"We use Class B insulation (130 degrees, C) for extra protection - UL listed as a Class A
(105 degree, C) design"
The class B winding means it will handle a little more abuse than the original tx, probably all it needs to prevent it popping.
What's probably going on is the original tx is rated correctly but it is mounted in one of those low-profile chassis where the heat can't get out. As a result the transformer fries or the thermal fuse opens when the amp is pushed. A few months back anotherjim posted a thread on a Peavey amp with a low-profile chassis shutting down when someone sat on it. (Of course you need different tx VA rating for different amp models. For a 30W amp you need about 50VA, which is what RG recommended.)
A loose end changing transformers is the fuse rating. It is possible the original tx has a one-shot thermal fuse (I dont' actually know) which pops when it overheats. I don't think those Hammonds will have a thermal fuse.
I think you may need higher voltage on the transformer to accommodate the drop in the power filter capacitor. 2200 µF seems like a really tiny number for a 1.15 amp drain. Using the equation:
CV = IT
where C is capacitance in Farads
V is voltage drop between alternations of the line voltage
I is supplied DC current in amps
T is time from one alternation to the other
C = 2200 µF
I = 1.15
T = 0.008333 seconds for 60 Hz and 0.01 seconds for 50 Hz
V = IT/C
which is 4.356 for 60 Hz
or 5.227 for 50 Hz
This is why you needed a 28 volt transformer where higher filtering would have permitted a 24 volt transformer. The voltage drops in the calculation above could be reduced by using a larger filter cap. It should be over 10,000 µF. The op amp, emitter follower and differential stages all have some power supply rejection but for full power, the output stage needs the voltage R.G. calculated to avoid hum modulation.
Quote from: Rob Strand on March 05, 2022, 12:03:02 AM
Quote from: pinkjimiphoton on March 02, 2022, 08:45:00 PM
RG was close, it needs a 28v center tapped transformer, 1 amp, like the hammond 166j28. it will fit the mounting holes, but this is the stock replacement for these suckahs!
The transformer in those amps appears to be on the edge as I've see number of posts regarding dead transformers.
That Hammond model you suggested could be somewhat better than the original. The specs for that transformer (and many other Hammond transformers) quote"
"We use Class B insulation (130 degrees, C) for extra protection - UL listed as a Class A
(105 degree, C) design"
The class B winding means it will handle a little more abuse than the original tx, probably all it needs to prevent it popping.
What's probably going on is the original tx is rated correctly but it is mounted in one of those low-profile chassis where the heat can't get out. As a result the transformer fries or the thermal fuse opens when the amp is pushed. A few months back anotherjim posted a thread on a Peavey amp with a low-profile chassis shutting down when someone sat on it. (Of course you need different tx VA rating for different amp models. For a 30W amp you need about 50VA, which is what RG recommended.)
A loose end changing transformers is the fuse rating. It is possible the original tx has a one-shot thermal fuse (I dont' actually know) which pops when it overheats. I don't think those Hammonds will have a thermal fuse.
there's no fuse in the originals. its funny, as the power supply and amplifier are virtually identical between the 12, 20,30 and to some extent the 50 watt models.
so far in the repairs i've made, i've had two dead transformers, both the secondary had popped on one side, usually the side that goes to the + of the diode bridge.
the filter caps are fairly small.... stock is 2200uf. i've been putting 4700u in, even 6600uf.... in the 12 watt reverb i did, i used three 2200 in parallel to get 6600 and the amp runs clean and cool with very little intermodulation and no crackles etc.
i ended up replacing all the resistors in the preamp with metal film to get rid of noise, too, which helped.
the 28vac works out to, after all the rectification and filtering to about 14.4-15.1 v on both the rails.
BUT some of them use a 9.1v zener in the driver section that drops the negative rail to about 10 volts. these seem to have a warmer and more bass heavy tone...
these are really weird little amps!
that hammond will work in the 12, 20, or 30 watt models. just be sure to ground the center tap to the chassis ground as well as the board ground. it will work without a chassis ground but it will be noisy and kinda dangerous... i was getting about 12-15vac on the chassis without it. the two red taps can go to either side of the secondary, doesn't matter.
the amp fuse is specc'd at 500ma, btw. it doesn't seem to draw very much.
hey rob, up for a challenge? i can post the top and bottom of the boards and the part values, if you are up to the epic/herculean/rockstar task of making a schematic, which does NOT exist for this model.
apparently i have the earlier version, maybe the earliest... its marked jm78-2 on the bottom of the pcb.
on the ssguitar amp forum, someone traced the preamp... but it doesn't match mine, or the other two "official" schematics.
crazy! ;)
i meant no dis to rg, of course... just saying. in the working amps i have, they all run about the same 28v
thanks for the explanation, ron
that helps me figure out how to "improve" these... cuz you're right, the hum can modulate the signal so badly you can get literal harmonization on some notes lol...i had one that sounded like you were playing in 5ths! ;)
bigger caps definitely help. i'll try going bigger and seeing if it helps. there's a distinct sonic improvement with 6600u than the 2200 that are stock.
the series of amps all use the same PT. according to marshall tech support, 28vac center tapped. it also matches the readings i took from the amps i've worked on. i have the 12 watt stack, the 12 watt reverb, the 30 watt non reverb, a DIFFERENT 30 watt non reverb <what i'm working on now, just a pcb someone had pulled> a 30 watt reverb, two 1x12 50 watt reverb combos, two of the 50 watt 2x12 combos, and two 50 watt headpieces.
i really dig this series of amps, and hard ;)
pics of the board. will upload a bom later. attempting to draw the circuit out, taking a bunch of notes.
but hopefully this'll help some other poor suckah on theyze one-way trip someday
(https://i.postimg.cc/gns33yMH/Resized-20220305-151118.jpg) (https://postimg.cc/gns33yMH)
(https://i.postimg.cc/TKPg0yFM/Resized-20220305-151233.jpg) (https://postimg.cc/TKPg0yFM)
(https://i.postimg.cc/v4S9NYw1/Resized-20220305-151303.jpg) (https://postimg.cc/v4S9NYw1)
(https://i.postimg.cc/Z9B3kGJw/Resized-20220305-151330.jpg) (https://postimg.cc/Z9B3kGJw)
(https://i.postimg.cc/V0R0B1Fk/Resized-20220305-151419.jpg) (https://postimg.cc/V0R0B1Fk)
(https://i.postimg.cc/yWzfPPTM/Resized-20220305-151452.jpg) (https://postimg.cc/yWzfPPTM)
(https://i.postimg.cc/14cvYqCf/Resized-20220305-151514.jpg) (https://postimg.cc/14cvYqCf)
(https://i.postimg.cc/dLs5MVpn/Resized-20220305-151514-1.jpg) (https://postimg.cc/dLs5MVpn)
(https://i.postimg.cc/sQCJTj5Y/Resized-20220305-151550.jpg) (https://postimg.cc/sQCJTj5Y)
(https://i.postimg.cc/N98kV3xW/Resized-20220305-151628.jpg) (https://postimg.cc/N98kV3xW)
(https://i.postimg.cc/N98kV3xW/Resized-20220305-151628.jpg) (https://postimg.cc/N98kV3xW)
(https://i.postimg.cc/t1W3ZK8Y/Resized-20220305-151653.jpg) (https://postimg.cc/t1W3ZK8Y)
(https://i.postimg.cc/9R2GGxj1/Resized-20220305-151752.jpg) (https://postimg.cc/9R2GGxj1)
(https://i.postimg.cc/c6sRC5hL/Resized-20220305-151722.jpg) (https://postimg.cc/c6sRC5hL)
(https://i.postimg.cc/G9qkyJgJ/Resized-20220305-151827.jpg) (https://postimg.cc/G9qkyJgJ)
(https://i.postimg.cc/HVnb4cfG/Resized-20220305-151858.jpg) (https://postimg.cc/HVnb4cfG)
(https://i.postimg.cc/Snz8H0SD/Resized-20220305-151921.jpg) (https://postimg.cc/Snz8H0SD)
(https://i.postimg.cc/rKHxhykD/Resized-20220305-152056.jpg) (https://postimg.cc/rKHxhykD)
(https://i.postimg.cc/FfySsjJS/Resized-20220305-152143.jpg) (https://postimg.cc/FfySsjJS)
(https://i.postimg.cc/jwR7WLzF/Resized-20220305-152341.jpg) (https://postimg.cc/jwR7WLzF)
I'm in the process of shifting PC's ATM so I can't do any tracing.
As far as I can tell, your board *is* a 30W unit. It has two TO-3 output transistors and
heatsinks with fins on all four sides.
What I can tell you is the Marshall schematics you find on-line are 'sort of' correct. I don't know what the hell goes on with their schematics but here's the general way forward using schematics and boards from that era.
- Find the schematic which matches the board as close a possible. (not straight forward)
You will then find:
- the schematic mostly matches
- the parts designators on the PCB don' t match-up with the schematic!
- when the schematic doesn't match you will find minor mods to the circuit
- in some cases the shape of the circuit matches the schematic but the part values are different.
All-in-all a big mess.
At least two people have put-up revised schematics for the 12W versions.
So start with Solid-state, 30W, no reverb, which is this schematic,
(https://i.postimg.cc/TpRTjfSX/Marshall-5010-30-W-sch.gif) (https://postimg.cc/TpRTjfSX)
You can see it sort of matches this part of the circuit,
https://postimg.cc/9R2GGxj1
The top half of the board is the power amp you can see the 10 ohm, 39 ohm and 1k5 ohm resistor. Then notice
the designators of the 1k5's not match up with the schematic. You can also see C21 on PCB (100uF 25V) doesn't
match with C22 on the schematic.
The lower half of the board is the preamp:
R1 is 220k on the schematic and 1M on the PCB.
Next you have the 2x68ks on the PCB so some small change there.
The other parts around IC1 match-up with the schematic.
I think you get the general idea. If you take that schematic you can kind of fumble through the PCB.
One difference is your PCB is marked JM78-2 whereas the schematic implies the PCB is JMP27A.
FWIW, the 50W models have a different transformer (larger, higher VA) and probably a higher voltage.
The TX would be likely be 70VA to 100VA. The back panel on the amp is marked 72VA but you
can't read too much into that.
Quote from: amptramp on March 05, 2022, 08:39:04 AM.... 2200 µF seems like a really tiny number for a 1.15 amp drain.... 4.356[V] for 60 Hz ... ...should be over 10,000 µF. .... hum modulation.
10,000uFd is a starter for Hi-Fi.
Popular-price stage amps have never run that much. 2,200uFd is reasonable for a 8 Ohm loading. 15% ripple is commercially acceptable (it won't drive-away customers).
Also even a mad shredder can't hold 1.15 Amps steady. Not even half of that for a whole second.
here's the BOM from the board i have,
hope it helps someone. still working on trying to draw up the schematic, wonky eyes suck!
5010 early version BOM
board jm78-2
vr1 gain b22k
vr2 volume al00k
vr3 treble b220k
vr4 mids b22k
vr5 bass a1m
vr6 pres b22k
ic 1 mc1458e
q1 bc184
q2 bc182
q3 bc182
q4 bc212
q5 bc184
q6 mj3001 darlington
q7 mj2501 darlington
zd1 9.1v <4739>
u
db1 br62
r= red box cap
t= tantalum
e= electro
c= ceramic
c1 47n@250 r
c2 2.2u@35 t
c3 2.2u@35 t
c4 2.2n c
c5 100n c
c6 2.2u@35 t
c7 2.2n c
c8 220n@100 r
c9 4.7n c
c10 220p c
c11 47n@250 r
c12 47n@250 r
c13 22n@400 r
c14 2.2u@35 t
c15 100u@25 e
c16 100u@25 e
c17 220n@100 r
c18 22u@25 e, axial
c19 2.2n c
c20 220p c
c21 100u@25 e, axial
c22 non existant
c23 2200u@25 e, radial
c24 2200u@25 e, radial
all resistors 5% cc 1/4 watt unless specified
r1 1m
r2 68k
r3 68k
r4 10k
r5 100r
r6 22k
r7 10k
r8 470r
r9 non existant
r10 22k
r11 68k
r12 10k
r13 33k
r14 4.7k
r15 2.7k
r16 2.7k
r17 10r
r18 6r 1 watt
r19 270r 3 watt
r20 470r
r21 10k
r22 3.9k
r23 4.7k
r24 680r
r25 10r
r26 2.2k
r27 1.5k
r28 1.5k
r29 1.5k
r30 10r
r31 39r
Quote from: Rob Strand on March 05, 2022, 10:45:19 PM
I'm in the process of shifting PC's ATM so I can't do any tracing.
As far as I can tell, your board *is* a 30W unit. It has two TO-3 output transistors and
heatsinks with fins on all four sides.
What I can tell you is the Marshall schematics you find on-line are 'sort of' correct. I don't know what the hell goes on with their schematics but here's the general way forward using schematics and boards from that era.
- Find the schematic which matches the board as close a possible. (not straight forward)
You will then find:
- the schematic mostly matches
- the parts designators on the PCB don' t match-up with the schematic!
- when the schematic doesn't match you will find minor mods to the circuit
- in some cases the shape of the circuit matches the schematic but the part values are different.
All-in-all a big mess.
At least two people have put-up revised schematics for the 12W versions.
So start with Solid-state, 30W, no reverb, which is this schematic,
(https://i.postimg.cc/TpRTjfSX/Marshall-5010-30-W-sch.gif) (https://postimg.cc/TpRTjfSX)
You can see it sort of matches this part of the circuit,
https://postimg.cc/9R2GGxj1
The top half of the board is the power amp you can see the 10 ohm, 39 ohm and 1k5 ohm resistor. Then notice
the designators of the 1k5's not match up with the schematic. You can also see C21 on PCB (100uF 25V) doesn't
match with C22 on the schematic.
The lower half of the board is the preamp:
R1 is 220k on the schematic and 1M on the PCB.
Next you have the 2x68ks on the PCB so some small change there.
The other parts around IC1 match-up with the schematic.
I think you get the general idea. If you take that schematic you can kind of fumble through the PCB.
One difference is your PCB is marked JM78-2 whereas the schematic implies the PCB is JMP27A.
FWIW, the 50W models have a different transformer (larger, higher VA) and probably a higher voltage.
The TX would be likely be 70VA to 100VA. The back panel on the amp is marked 72VA but you
can't read too much into that.
hey bro, yeah i can grok the pc thing, i just had to get a new one recently and am hating life lol
the 50 watters do use a bigger transformer, but its the same one in the 12-20-30 watt models, believe it or not. for all intents, the actual amplifiers are all but virtually the same.
the diff is actually the speaker load!
16 r, 12 watts
8r, 20 watts
4r, 30 watts..... seriously, if ya look at the schematics, they're almost identical!
i think the main dif between the posted common schematic is everything is off a little bit from the way the input is set up. it puts all the parts numbering off a couple numbers. most of it is VERY similar, in term of layout, but some of the part values are different.
i'm gonna shoot marshall an email and beg for the schematic, i'd rather at least try that than trace it on my own. if they can't help, i'll bite the bullet.
i've begun drawing it up, and taking notes... gonna probably take a while, tho, cuz i really suck at doing this stuff.
on a side note, i'm not getting notifications on forum posts all the sudden, really weird!!
Quotethe 50 watters do use a bigger transformer, but its the same one in the 12-20-30 watt models, believe it or not. for all intents, the actual amplifiers are all but virtually the same.
the diff is actually the speaker load!
16 r, 12 watts
8r, 20 watts
4r, 30 watts..... seriously, if ya look at the schematics, they're almost identical!
I don't doubt it. The fact they aren't exactly the same is the source of screwing up the part designators.
This was one of the "corrected" schematics for the 12W. IIRC, there was another schematic by a Japanese guy.
(https://i.postimg.cc/645dCgJf/Marshall-5005-corrections-to-3005-schem-image-46574.gif) (https://postimg.cc/645dCgJf)
Not sure how useful it is as it suffers the designator mismatch issue. Notice also, even on this corrected schematic the part values have the 330k from the original schematic, whereas your PCB clearly has a 1M input resistor.
It would be interesting to see if Marshall can give you a matching schematic. Perhaps quote your PCB number of JM78-2 if it helps. Otherwise I suspect they will send you the schem which is already on the web.
I wonder about the <500k input resistors in these SS amps and indeed all others with opamps with 741 DNA. Even up to the RC4558. Possibly they were designed before or during the appearance of overwound hi-z humbuckers from DiMarzio et al.
But what was the rationale for not going with 1M resistors? To satisfy the input bias current of those opamps? So if you wanted 1M, you'd probably best change to a TL072, but that probably defeats the 741 sound that Jimi likes.
Lower noise and a bit more treble rolloff in the input? Can't see why that would hurt in a high-ish gain amp.
Many Peavey amps work great with about 500k too and the classic Fender input stage has mere 66k if you plug to the other input jack.
Quote from: Rob Strand on March 06, 2022, 05:21:21 PM
Quotethe 50 watters do use a bigger transformer, but its the same one in the 12-20-30 watt models, believe it or not. for all intents, the actual amplifiers are all but virtually the same.
the diff is actually the speaker load!
16 r, 12 watts
8r, 20 watts
4r, 30 watts..... seriously, if ya look at the schematics, they're almost identical!
I don't doubt it. The fact they aren't exactly the same is the source of screwing up the part designators.
This was one of the "corrected" schematics for the 12W. IIRC, there was another schematic by a Japanese guy.
(https://i.postimg.cc/645dCgJf/Marshall-5005-corrections-to-3005-schem-image-46574.gif) (https://postimg.cc/645dCgJf)
Not sure how useful it is as it suffers the designator mismatch issue. Notice also, even on this corrected schematic the part values have the 330k from the original schematic, whereas your PCB clearly has a 1M input resistor.
It would be interesting to see if Marshall can give you a matching schematic. Perhaps quote your PCB number of JM78-2 if it helps. Otherwise I suspect they will send you the schem which is already on the web.
i did contact marshall, no reply yet. i'm in process of tracing the mess. got the input stage, part of the preamp, and tone stack so far.
we'll see what happens. i can only go so long before my eyes just give out. anything i need to see detail on is problematic.
the tone stack matches the schematic, at least the layout does... the values are a bit different.
i gotta pull my other 30 watter apart and see if its the same.
i haven't looked at it in a long time, hoping it IS a match so i can use its front panel to help me draw up where to put the holes for the blank chassis i bought last nite.
still not being notified. very weird. i'll post news when i find some.
Quote from: anotherjim on March 08, 2022, 07:26:05 AM
I wonder about the <500k input resistors in these SS amps and indeed all others with opamps with 741 DNA. Even up to the RC4558. Possibly they were designed before or during the appearance of overwound hi-z humbuckers from DiMarzio et al.
But what was the rationale for not going with 1M resistors? To satisfy the input bias current of those opamps? So if you wanted 1M, you'd probably best change to a TL072, but that probably defeats the 741 sound that Jimi likes.
tl072's sound like ass in this circuit. they don't clip gracefully, they tend to sound like broken glass... and they have just plain too much high end response. maybe good for some things, but in this circuit, all that means is an assload of hiss. not good.
one of my 5212's that had come in had been modified. it sounded good clean, but if cranked was so damn hissy it was horrible, brittle, and unuseable. i don't wanna have to use a noise gate... this thing was so damn noisy tho i had to. the guys in the band bitched. if i had to mic it outdoors, the sound guy and audience would bitch.
i opened it up, saw a bunch of sockets. every single one was loaded with 072's. i replaced them with the proper chips, and the amp came to life. better warmer distortion, no more broken glass or hiss.
the mojo-istic belief that them jfets sound better is just more internet hubris. its simply not true. in SOME circuits, they can sound great. but not in these marshalls. they're horrible in this circuit. i tend to find that tho i DO like mosfets in distortion, i totally despise jfets unless they're clean. they just plain don't sound good.
yeah, they may mimic a tube's amplification curves somewhat, when CLEAN, when they clip? they clip super hard and ugly. no bueno!
the 1458's don't have that broken glass thing, and don't waste power producing loud hiss a couple octaves higher than the guitar signal resides.
funny, many of my friends tend to agree on this. there's really a world of tonal difference. almost any dirt pedal will sound better with a 741 or 1458 than any jfet dirt circuit. ymmv, and should, of course...
but i'm working in the real world with these things, not playing in my room or at my bench. stuff often sounds vastly different at stage volume.
i think the biasing is to make 'em sag a bit more. these chips also sound better when browned out some. i'll stick with the guv'nor on this one! ;)
I'm with you Jimi, I wouldn't use any TL chip if I think it can run in to clip. The thing I don't get is why not fit 1M. MXR D+ is 1M and a 741 although a dirt box is perhaps a poor example.
Too much treble? We have a tone knob on the guitar.
Too noisy? Ermm, as I understand it, the quietest resistor is no resistor.
In series, that's 0 ohms or wire. In parallel, it's infinity ohms or nothing. So 1M or higher even isn't noisy in itself for the parallel fit, but I think opamps have a spec about input noise that's dependent on the source impedance which is lower = quieter. I don't understand the mechanics of how that works but a lower value parallel input resistor will lower the source impedance seen by the opamp - guitar pickup impedance is relatively low but can go higher: 250k if I turn a 500k vol knob on a Gibson with one pup on to half resistance and 125k with a Fender 250k. A 330k input resistor will roughly halve the source impedance then. This is when the TL072 beats others at 1M , it doesn't get so noisy if the guitar is at a high impedance.
I've modded a Peavey to 1M because it was dull with high output 'buckers but I never considered changing the stock input opamp since the other half is in the overdrive circuit.
> a lower value parallel input resistor will lower the source impedance seen by the opamp
AND lower the desired signal. (Or rather: you will turn-up to get the desired level.)
Trying to "lower node impedance" with a shunt resistor is self-defeating.
The shunt resistor should be as high as possible.
Quote from: anotherjim on March 08, 2022, 02:34:38 PM
I'm with you Jimi, I wouldn't use any TL chip if I think it can run in to clip. The thing I don't get is why not fit 1M. MXR D+ is 1M and a 741 although a dirt box is perhaps a poor example.
Too much treble? We have a tone knob on the guitar.
Too noisy? Ermm, as I understand it, the quietest resistor is no resistor.
In series, that's 0 ohms or wire. In parallel, it's infinity ohms or nothing. So 1M or higher even isn't noisy in itself for the parallel fit, but I think opamps have a spec about input noise that's dependent on the source impedance which is lower = quieter. I don't understand the mechanics of how that works but a lower value parallel input resistor will lower the source impedance seen by the opamp - guitar pickup impedance is relatively low but can go higher: 250k if I turn a 500k vol knob on a Gibson with one pup on to half resistance and 125k with a Fender 250k. A 330k input resistor will roughly halve the source impedance then. This is when the TL072 beats others at 1M , it doesn't get so noisy if the guitar is at a high impedance.
I've modded a Peavey to 1M because it was dull with high output 'buckers but I never considered changing the stock input opamp since the other half is in the overdrive circuit.
well, remember, this is supposed to be in an amp that is supposed to be a marshall, so they're likely using the values they chose to get as "close" as they could tonally, as well as in the effective range of the controls. its not a stompbox, so perfection ain't likely. it was built to meet a price point! ;)
i think you're misunderstanding me. when you push a tl into clipping, it clips hard and ugly.
the reason it has more noise/hiss is because its effective frequency range goes much higher than the 741 can. so you're putting out an extra octave or more of treble, above the range of the guitar, which manifests itself as a really loud, annoying HISSSSSSSSSSSSSSS that won't go away.
the only way these amps really sound good is with the gain pegged. below that, they're nothing really special. but when you crank the gain to get the max distortion possible <which cleans up really well when ya roll your guitar back> that extra treble gets distorted and manifests in a most unmusical way.
its not the resistors. that's not the issue. the issue is the amount of gain, and the jfet based chips clipping hard and ungracefully, but most especially the frequency range.
a 741 when clipped acts very differently from a tl071. in the case of this particular circuit, the "worse-er" specs sound way better.
peeps make "laws" that they often don't understand... often based on internet hype and mojo.
who in @#$% wants a "hifi" distortion? that's kind of defeating the purpose.
even a klon(e) sounds better with the bjt based opamps to my ear. warmer distortion, better cleanup from the guitar etc.
i see peeps add tl's cuz the internet tells them they sound better. not based on them LISTENING CRITICALLY to the results. to me, if ya put a tl072 in a toob skreemer, it just sounds even worse than the stock 4558 does. too much glass, too much high end, too hissy. no bueno.
so tho the resistors may make a difference in the biasing of the circuit truly, ultimately it still comes down to the magick jelly bean in there.
the XX58's just plain sound more musical in distortion than the more "hifi" jfet ones.
jfets sound great clean. but they really sound like crap in most cases with dirt. they sound ok til they flatline. and when they do, they make a horrid racket, at least to my ears.
on a side note, i got a reply from marshall.... the ONLY schematic they have is for the one that's already out there.
so far, i've got the input stage and the tone stack drawn up for this specific circuit. its gonna take a while. glaucoma and long traces that twist around in box shapes tend to really mess me up.
rock on!
I was only trying to discuss why the input impedance should be low since 1M was already a standard and nobody really took me up on it! I'm not convinced by any arguments for lowering it. I wasn't ever suggesting you should change the opamps, only mentioning the TL07x as a way to have 1M input without too much noise then your character opamps can take over. There are tube amps with TL072 input buffers and they can sound pretty good.
Oh, and I got my pot resistance maths wrong earlier too. Really surprised I got away with that. A 500k volume pot becomes a 125k source at half resistance, doesn't it?
Quote from: anotherjim on March 10, 2022, 05:30:56 AM
I was only trying to discuss why the input impedance should be low since 1M was already a standard and nobody really took me up on it! I'm not convinced by any arguments for lowering it. I wasn't ever suggesting you should change the opamps, only mentioning the TL07x as a way to have 1M input without too much noise then your character opamps can take over. There are tube amps with TL072 input buffers and they can sound pretty good.
Oh, and I got my pot resistance maths wrong earlier too. Really surprised I got away with that. A 500k volume pot becomes a 125k source at half resistance, doesn't it?
you're speaking to a monkey with a breadboard, bro..... what? lol
Quote from: anotherjim on March 10, 2022, 05:30:56 AM...A 500k volume pot becomes a 125k source at half resistance, doesn't it?
Yes, and who cares? Pot at half, you have already thrown-away half your signal level.
If you play LOUD, nobody hears your hiss.
Quote from: PRR on March 10, 2022, 01:02:38 PM
Quote from: anotherjim on March 10, 2022, 05:30:56 AM...A 500k volume pot becomes a 125k source at half resistance, doesn't it?
Yes, and who cares? Pot at half, you have already thrown-away half your signal level.
If you play LOUD, nobody hears your hiss.
hahahah, oh yes, they do. that's what led to me opening the amp and discovering the culprits... tl072's where 1458's should be.
with the gain cranked, it was unuseable, and believe me, i wasn't being quiet.
outside in particular where i needed to mic it it was especially bad.
once i changed the jellybeans back to what they should have been, the hiss literally disappeared. like turning the gain from dimed to rolled back to about half way. significant change in noise and hiss.
when i use these suckers, believe me, they're cranked. gain and volume on 10, tone stacks roughly 6 across the board, and master volume between 4 and pegged. i go in and blueprint 'em with 1% metal film flameproof resistors to get the noise down. it makes a big dif.
but the change was so significant even the deafest members of the band noticed it immediately, as it had become a bit of an inside joke. and the sound guys always bitched, lol...
no more problem.
the tl072's so many people think "sound better" simply don't in this application. they're ok with the master volume way down, but once you're half way up, the noise makes it unuseable without using a noise gate, which completely destroys the tone that makes these worthwhile in the first place.
(https://i.postimg.cc/n9hYXMjd/Marshall-5010-PCB-78-2-Schematic-Draft1.jpg) (https://postimg.cc/n9hYXMjd)
thanks to tassieviking on ssguitar, appears they worked up a schematic from my pics
(https://i.postimg.cc/n9hYXMjd/Marshall-5010-PCB-78-2-Schematic-Draft1.jpg) (https://postimg.cc/n9hYXMjd)
(https://i.postimg.cc/VSFCXmc2/Marshall-5010-78-2-PCB-Schematic-Draft.png) (https://postimg.cc/VSFCXmc2)
Quotethanks to tassieviking on ssguitar, appears they worked up a schematic from my pics
Cool. Thanks jimi and tassieviking.
I have *not* checked the trace/schem, however, the input stage didn't look 100% correct.
The no input cap is correct but the arrangement at the output of the first stage of IC1 looked wrong.
I posted the correction below. The fix actually follows the other 5010 schem fairly closely, the only
difference is the other 5010 schem has an extra 100R on the output of IC1.
Bug on schematic Rev 1, 2022-03-19
(IC1 pin 7 goes to C4 (100p) and R6 (22k) as shown)
But then from IC7 pin 7 it should go,
IC7 pin 7 to C2+
C2- to paralleled C1 (47n) & R4 (10k)
other side of paralleled C1 (47n) & R4 (10k)
to VR1.1 (ccw)
and to IC1 pin 3
I can't make out the detail around C1, C2, R4 very clearly, but I believe I am right.
Here are some of the pics I worked with, I have mirrored the track side so it easier to compare to the component side.
I did find the inputs wired wrong, the middle pot reversed and R18 wired wrong, fixed for draft 2
(https://i.postimg.cc/ZWrPTzdS/Marshall-5010-PCB-78-2-Schematic-Draft-2.jpg) (https://postimg.cc/ZWrPTzdS)
(https://i.postimg.cc/Z0CrWddj/Marshall-5010-PCB-78-2-Track-Side-enlarged-IC1.jpg) (https://postimg.cc/Z0CrWddj)
(https://i.postimg.cc/5Hytsw1R/Marshall-5010-PCB-78-2-Track-Side-Image-Mirrored.jpg) (https://postimg.cc/5Hytsw1R)
QuoteI can't make out the detail around C1, C2, R4 very clearly, but I believe I am right.
On the PCB, the lower sides of C1 and R4 have separate tracks, which are easily visible.
What's hard to see is the short track which joins the lower side of C1 and lower side of R4.
As drawn the circuit cannot work:
- IC1 pin 3 has no bias path to ground.
- the volume control (VR1) cannot make the volume go to zero.
That's the purpose of R4, it appears in series with the output of IC1 pin 7
so VR1 can short the signal to ground when VR1 is set to the minimum position.
It's a common circuit (also used of Peavey amps) and is used on the "other" 5010 schematic
given earlier in thread (C6 and R6, R5 not present):
https://www.drtube.com/schematics/marshall/5010.gif
EDIT:
It occurred to me later Jimi posted a few pics of that area of the pcb earlier on in the thread
For example, on the right hand side of this pic you can see a thick track joining C1 and R4. It's the same thickness track that joins the top of C1 and R4.
(this pic is not flipped to emulate an x-ray view)
https://postimg.cc/t1W3ZK8Y
gentlemens....
here's the deal. tassieviking's schematic, the last one, has only one mistake.
r4 10k and c1 47n are in parallel. one node connects to negative side c2/gain pin 1, the other to pin 3 of the 1458.
other than that, matches the circuitboard i have on my bench as far as i can tell completely, and am absolutely sure the preamp is right other than that one spot.
its hard to see. there's a couple traces that may not look connected cuz of the way the board was laid out, and cuzza that sticker that i hadn't removed from an inspector.
here's a pic, i drew lines to show the connections, and filled in the blanks with the part #'s and values
(https://i.postimg.cc/mPpbH6PT/Resized-20220320-232132.jpg) (https://postimg.cc/mPpbH6PT)
(https://i.postimg.cc/DWW7ddGL/Resized-20220320-232256.jpg) (https://postimg.cc/DWW7ddGL)
(https://i.postimg.cc/GBZdM8PN/Resized-20220320-232301.jpg) (https://postimg.cc/GBZdM8PN)
(https://i.postimg.cc/8JMDxptC/Resized-20220320-232304.jpg) (https://postimg.cc/8JMDxptC)
(https://i.postimg.cc/Cn0Yg3Qs/Resized-20220320-232309.jpg) (https://postimg.cc/Cn0Yg3Qs)
Quotehere's the deal. tassieviking's schematic, the last one, has only one mistake.
r4 10k and c1 47n are in parallel. one node connects to negative side c2/gain pin 1, the other to pin 3 of the 1458.
other than that, matches the circuitboard i have on my bench as far as i can tell completely, and am absolutely sure the preamp is right other than that one spot.
Good on you Jimi! Thanks for checking.
I stand corrected, I could see a darkness in that area, but I could not see if it was a trace or not on the photos I was checking.
Thanks for the new photos pinkjimiphoton, it cleared it right up.
I have updated the schematic to draft 3, but I had already made the inputs as stereo jacks and I can't be bothered to change them back right now.
If I make up a PCB I always use stereo jacks just for the added strength so the solder is less likely to crack with use.
It might be silly, but I feel why not add the extra 50% solder connections to hold the jacks steady.
Once we have the schematic correct, I will post it up as a final.
Then the fun might start, what mods could be made if I make up the PCB and go to get some made ?
Effect loop for sure, but what circuit do I add, reverb ?
But that's for later
Here is Marshall 5010 PCB 78-2 Schematic draft 3 :
(https://i.postimg.cc/ppCMt0tr/Marshall-5010-PCB-78-2-Schematic-Draft-3.jpg) (https://postimg.cc/ppCMt0tr)
(https://i.postimg.cc/CRWgvRgs/Marshall-5010-78-2-PCB-Schematic-Draft-3.png) (https://postimg.cc/CRWgvRgs)
Quote from: Tassieviking on March 21, 2022, 04:31:38 AM
I stand corrected, I could see a darkness in that area, but I could not see if it was a trace or not on the photos I was checking.
Thanks for the new photos pinkjimiphoton, it cleared it right up.
I have updated the schematic to draft 3, but I had already made the inputs as stereo jacks and I can't be bothered to change them back right now.
If I make up a PCB I always use stereo jacks just for the added strength so the solder is less likely to crack with use.
It might be silly, but I feel why not add the extra 50% solder connections to hold the jacks steady.
Once we have the schematic correct, I will post it up as a final.
Then the fun might start, what mods could be made if I make up the PCB and go to get some made ?
Effect loop for sure, but what circuit do I add, reverb ?
But that's for later
Here is Marshall 5010 PCB 78-2 Schematic draft 3 :
(https://i.postimg.cc/ppCMt0tr/Marshall-5010-PCB-78-2-Schematic-Draft-3.jpg) (https://postimg.cc/ppCMt0tr)
(https://i.postimg.cc/CRWgvRgs/Marshall-5010-78-2-PCB-Schematic-Draft-3.png) (https://postimg.cc/CRWgvRgs)
bro, i forgot to mention, the measurements for the jack spacings are from the bottom, from the left edge to pin one of each of the switching jacks.
i agree, switching jacks make way more sense, and are way more robust.
i really like the guitarpcb.com paramix for adding loops to this circuit, it works well, is cheap and easy, and ya get a series loop as well as an adjustable parallel one.
proper reverb tank for the 30 watt or 12 watt reverb circuit appears to be the P-RMOD 8FB3C1B is a very close reverb pan that will work well with the circuit, antique electronic supply has them, if anyone else contacts you about it... should also work with the 12 watt reverb combo, which is what i used to replace mine. the stock 30 watt reverb and the marshall 12r both use a crappy spring unit that mounts right on the pcb and is prone to feedback if it works at all ;)
excellent work. you rock, bro!
very stoked. with your permission, when all ends off, if its cool i'll send a copy to marshall for their archive, as they do NOT have this circuit archived.
hey tassieviking, i think i found one other mistake... i guess i was unclear in my description, and i just noticed it.
pin 1 of the gain pot connects to node of 10k and 47n on the 2.2uf tantalum side. so it's still off by that one connection. the 10k r4 and 47n c1 are in parallel. ONLY one side of them connects to pin 3 of the jelly bean.
the gain pot pin 1 connects to the other node, where the "input" of the rc network connects to the 2.2uf tant.
i did a q&d paint fix on it, this is how it needs to be:
(https://i.postimg.cc/njT7jsXs/Marshall-5010-PCB-78-2-Schematic-Draft-3-b.jpg) (https://postimg.cc/njT7jsXs)
Quotepin 1 of the gain pot connects to node of 10k and 47n on the 2.2uf tantalum side. so it's still off by that one connection. the 10k r4 and 47n c1 are in parallel. ONLY one side of them connects to pin 3 of the jelly bean.
the gain pot pin 1 connects to the other node, where the "input" of the rc network connects to the 2.2uf tant.
i did a q&d paint fixon it, this is how it needs to be:
That doesn't look right.
The R4 and C1 connections on Draft 3 look ok to me.
The tracks fork off at R4 and C1. One path goes to IC1 pin 3 the other goes to VR1 pin 1.
The two parts,
https://postimg.cc/mPpbH6PT
On the right is R4 and C1 then a bit to the left is IC1, below IC1 and to left a bit more is VR1
https://postimg.cc/t1W3ZK8Y
nope. it's exactly as i changed it to on the last schematic. the gain pot doesn't connect directly to pin 3. it connects on the other side of the r4/c1 network. i checked it against the actual board, unless i'm losing my mind, which IS possible.
i'll look again at it, but r4/c1 are in parallel. one side connects to the neg side of the 2.2u tant. that's where pin 1 of the gain pot goes. the other side of the r4/c1 network connect directly to pin 3 of ic 1.
i'll beep it out to be sure when i get back to my bench. but that was also what i drew when i first started drawing it out myself. its one of the differences between this and the other two boards that are out there.
gimme a bit, stay tuned...
Quotenope. it's exactly as i changed it to on the last schematic. the gain pot doesn't connect directly to pin 3. it connects on the other side of the r4/c1 network. i checked it against the actual board, unless i'm losing my mind, which IS possible.
i'll look again at it, but r4/c1 are in parallel. one side connects to the neg side of the 2.2u tant. that's where pin 1 of the gain pot goes. the other side of the r4/c1 network connect directly to pin 3 of ic 1.
i'll beep it out to be sure when i get back to my bench. but that was also what i drew when i first started drawing it out myself. its one of the differences between this and the other two boards that are out there.
gimme a bit, stay tuned...
I can see the connections very clearly on the PCB on your earlier pic and the follow the Draft 3 connections.
Lower side (ie. side closest to the pots) of R4/C1 go to IC1 pin 3 and VR1 pin 1 (counter-clockwise).
Should be able to buzz it out with continuity.
looking at it, yer right i think
i will beep just to be sure, cuz sometimes pics can be decieving i find with pcb pix
(https://i.postimg.cc/PLHtR6Rn/Resized-20220305-151653.jpg) (https://postimg.cc/PLHtR6Rn)
Quotelooking at it, yer right i think
i will beep just to be sure, cuz sometimes pics can be decieving i find with pcb pix
Those trace lines are how I see it.
The fork in the PCB tracks puts you off.
too much crap on my bench. yes, i AM brIAn dead.
somehow i was confusing myself. pin 1 of gain r4 and c1 in parallel at pin 3 of ic, other side to c2 to pin 7.
rev 3 is the one. sorry for the confusion.
2 marshalls, a tube works head, my ps systems power tool and a bx13 24 pin to 13 pin midi guitar adapter kinda all going at once....
yikes! :icon_mrgreen:
Quotetoo much crap on my bench. yes, i AM brIAn dead.
somehow i was confusing myself. pin 1 of gain r4 and c1 in parallel at pin 3 of ic, other side to c2 to pin 7.
rev 3 is the one. sorry for the confusion.
2 marshalls, a tube works head, my ps systems power tool and a bx13 24 pin to 13 pin midi guitar adapter kinda all going at once....
yikes!
No worries, thanks for checking all the stuff. Tracing PCBs never gets any easier. Many eyes certainly helps knock out the bugs.
Fingers crossed that it is right this time.
(https://i.postimg.cc/CZN4P97g/Marshall-5010-PCB-78-2-Schematic-Final.jpg) (https://postimg.cc/CZN4P97g)
(https://i.postimg.cc/LY5jy5ht/Marshall-5010-78-2-PCB-Schematic-Final.png) (https://postimg.cc/LY5jy5ht)
confirmed!
working schematic for the marshall 5010 pcb78-2, thanks tassieviking and rob strand!
gotta get measurements still, they're written on my bench buried somewhere i have to find it, had to dig thru bags of parts
looking for other parts ;)
the pcb i had "for parts" has had the power supply rebuilt, and works great. got it mounted in a hammond aluminIum box of 17x3x6" with the proper transformer, a real power supply jack and lighted switch, thanks to a nibbler i got that i don't believe i've lived without for all these many years...
drove me literally bat-shit insane last nite. it was kinda passing signal, poorly, motorboating like crazy, etc...
found a bad solder :icon_redface: on the ground side of a filter cap, fixed that, the hum continued.
i was bringing it up on my variac. it was humming horrible. and sounded like it was gonna blow up, so i didn't juice it ...
then it hit me... dumbass... its transistors, NOT TUBES.
TUBES may fire at 20 or 30 volts, at least a little.
transistors that are designed to be run at 28v ptp wanna see 28v to bias. not, like, 4 or 6.
i rebuilt it twice before i figured out the damn thing was completely misbiased.
whipped it up to 110 and suddenly the damn thing worked perfect.
:icon_rolleyes: :icon_redface: :icon_eek: :icon_evil: :-[ :o
anyways, its in a box and functional. the "presence" control would make a great treble booster, i may add it to some of the other amps.
(https://i.postimg.cc/YG7Dhsgt/marshall-treble-boost-presence-control-deet.jpg) (https://postimg.cc/YG7Dhsgt)
video0-no
part 1
part deux
I have nearly completed the PCB now, the way I like it.
It' as close as I can get it without actually holding it in my hands.
pinkjimiphoton, Rob Strand -
Is it ok if I include your names on the finished PCB for when I post all the KiCad files.
Like this PDF document shows.
(https://i.postimg.cc/F7QNZSb2/Marshall-5010-78-2-PCB-Final-Dimensions.png) (https://postimg.cc/F7QNZSb2)
that is beautiful!!!
hell yes, i'd be honored, bro!!
i'd definitely buy a couple boards when you get some if ya need an investor!
thank you so much for doing this!
QuoteI have nearly completed the PCB now, the way I like it.
It' as close as I can get it without actually holding it in my hands.
The whole PCB, that's impressive!
Quotepinkjimiphoton, Rob Strand -
Is it ok if I include your names on the finished PCB for when I post all the KiCad files.
It's OK with me but I don't feel worthy ;D. You did 99.9% of the hard work.
I think I got it close, here are my files on it.
(https://i.postimg.cc/FYMRD3BJ/Marshall-5010-PCB-78-2-Schematic.jpg) (https://postimg.cc/FYMRD3BJ)
(https://i.postimg.cc/7CSLchFt/Marshall-5010-PCB78-2-3-D-Front.jpg) (https://postimg.cc/7CSLchFt)
(https://i.postimg.cc/8spCK1tw/Marshall-5010-PCB78-2-3-D-Front-45.jpg) (https://postimg.cc/8spCK1tw)
(https://i.postimg.cc/T53Yp9pB/Marshall-5010-PCB78-2-3-D-Rear-45.jpg) (https://postimg.cc/T53Yp9pB)
(https://i.postimg.cc/GBnLkr4F/Marshall-5010-PCB78-2-3-D-Rear-45-Close.jpg) (https://postimg.cc/GBnLkr4F)
(https://i.postimg.cc/N9gQz47L/Marshall-5010-PCB78-2-3-D-top-view.jpg) (https://postimg.cc/N9gQz47L)
(https://i.postimg.cc/DSKH6zcw/Marshall-5010-PCB78-2-3-D-top-view-bare.jpg) (https://postimg.cc/DSKH6zcw)
(https://i.postimg.cc/dk4JPy46/Marshall-5010-PCB78-2-Dimensions.jpg) (https://postimg.cc/dk4JPy46)
I can't work out how to post ZIP files, so if you want the KiCad file or Gerber files you have to go to the Solid Stat Guitar forum to get them.
https://www.ssguitar.com/index.php?topic=5124.msg40134;topicseen#new
[/quote]
It's OK with me but I don't feel worthy ;D. You did 99.9% of the hard work.
[/quote]
Rob.
The Circuit would be useless with even 0.1% wrong.
I think your input was more then 0.1% anyway.
thanks Michael, that's some beautiful work, bro!!
i'm hoping to build a couple of these just for shits n grins.
i am super appreciative of your hard work on this project, and yes, rob's too damn humble sometimes ;)