Ludwig Phase II Clone Tech Notes

[pinkjimiphoton]

well..... some things are better...kinda.

just boxed it back up.

this thing is p***ing me off!

the FORMANTS are ABSOLUTELY working better.

but now the hum is back, and about an octave higher. and cyclical. it has gotta be lead dress, it's all i can think of. i mean, they have audio, power, and all running bundled together.
it's worse now than it was, unbelievable!! gonna try and open her up again, and see if i can play with it a little, but this thing is a bit beyond me, i think. wondering if changing the capacitance changed all the trimmers slightly or something...

i didn't change anything on the fall board, but it sounds like i did....all i can think of is maybe i gotta play with the trimmers again or something.

[pinkjimiphoton]

ok...i opened it back up and messed with it some. tomorrow,  i may open the top again, but starting to think i may as well leave well enough alone.

it's still acting kinda funky and noisy, but i think i can live with it.

one thing i DID find that helped nuke most of the hum is that r76 on the fall board, a 33k resistor, was reading open. it's supposed to connect the - side of c1 to ground.
so i replaced it with 27k, closest thing i had. didn't make a lick of difference.

however...grounding the negative side of c1 directly nuked 90% of the hum. weird, or what?

outside of some background noise and a little ticking tho, i think i can live with it...i have it dialed in where it pretty much has the yoy yoy yiy yiy yay yay thing down.

close enough for rock n roll for me!!

g'nite folks...peace and sweet dreams! 

[Keppy]

one thing i DID find that helped nuke most of the hum is that r76 on the fall board, a 33k resistor, was reading open. it's supposed to connect the - side of c1 to ground.

Is that the same capacitor you kept replacing earlier, the one you had to overrate the voltage on? Is this maybe a related issue?

[R.G.]

one thing i DID find that helped nuke most of the hum is that r76 on the fall board, a 33k resistor, was reading open. it's supposed to connect the - side of c1 to ground.
so i replaced it with 27k, closest thing i had. didn't make a lick of difference.

however...grounding the negative side of c1 directly nuked 90% of the hum. weird, or what?

R76 is a pull down resistor on the outside of C1, which is the input capacitor for the low-Z input. I suspect that R76 was a late addition to the PCB, stuck there to try to combat issues with the Low-Z input. It's a very high number, and it's put in a part of the circuit electrically and physically where the other resistor numbers are low. I bet it was put in way late in the design for some reason.

And since grounding C1 kills hum, I suspect that the hum is actually getting in through the wiring from the lo-Z input to that lo-Z balance pot. It may be that the pot is picking it up, or the wiring to it is running too close to the lamp AC, or that the ground to the low-Z input isn't, or the balance pot itself is messed up. Just guessing.

[digi2t]

this thing is p***ing me off!

Ya didn't think that this sucker was going to go down without a fight, now did ya? Jimi, bro, from the pics, your units in rough shape. Looks almost like the fall plate was underwater at some point. As a wise man told me, "Breathe, brother, breathe".

Does the hum go away if you disconnect the lights? Unplugging the feeder wire to the lamp resistor for example (tape the loose lead though). Hell, unplug and tape both green wires going to the motherboard for the lamps (pads 11 and 12), and try that.

one thing i DID find that helped nuke most of the hum is that r76 on the fall board, a 33k resistor, was reading open. it's supposed to connect the - side of c1 to ground.
so i replaced it with 27k, closest thing i had. didn't make a lick of difference.

Did you test directly across the resistor, or one side to a gnd. point? Maybe a cracked solder joint or trace?

Also, the input jacks are supposed to be switched to ground when not in use. Could there be a grounding problem there?

Also, Jimi, my bypass light is ON when in bypass, OFF when in effect. I believe you said that it was opposite of yours. Is this true?

[pinkjimiphoton]

hi guys.

i suspect it could be any of those things.

yes, keppy, that's the same one. at this point, it's a 10mf@250 volts!!!

yes, dino, it WAS opposite of yours, but i wired it the way yours was when i replaced the switch. i figured that was probably correct, so i went for it.

i will try nuking the ac to the lamps later and see if the noise goes away. most of it seems cyclical, and related to the formant filter, as adjusting the speed and intensity of that seems to affect the noise as well. it DOES have a good bit of carbon comp resistor "blow"...probably better to stick to metal resistors in the builds...not only for consistency, but noise, too. i believe they used so many cc just cuz especially back then, they were much cheaper.

i may be being hypercritical from too much caffiene, tiredness, and headphone ear. i suspect it will sound quieter thru the amp.

i'm still picking up sone cyclical noise...it was more noticeable cuz i was wearing headphones into a cranked v-amp. but the hum seems nuked.

i think r.g. was right, i think that r76 was a REAL late addition. here's the thing. replaced it with a 27k rather than the 33k just cuz it was what i had on hand. grounding one end of the 27 k resistor worked...until i soldered it in place! i tried to take the as yet uncut lead of the resistor that was going to the ground side and connect that to ground, and it made absolutlely no difference. i had to take the " hot" side of the resistor, literally directly off the "cold" side of the cap, and go directly to the same ground as the hi z jack. no more hum. so my question to you guys is this...how the hell can the input to the effect work if the audio path is being run directly to ground? it should be the same as turning down the volume on your guitar, right???

weird, or what?

that seems to me that "ground" is hot, and not at ground potential AT ALL.  bad transformer, maybe? also considering adding a modern "3 prong" grounded power cord.

i'll wait on that tho to see what shakes out.

beginning to seriously consider modification, using shielded wire from all audio on the fall board to the console board, and twisted pair multicore bundled wire to replace all the rest. shielded to/from jacks, switches, pots, anything that carries audio. and "telescoping" the grounds with that, maybe moving everything to a single ground buss wire for the whole unit.

of course, it may be over kill, and possibly not worth it...the spirit is willing, but the flesh is weak.


a couple other things i've noticed is that the fuzz has more balls than it did. alot more.
and it's almost unity now with the wah/formant when switched in and out, where before it was weaker and slightly below unity.
the whole pedal now is louder...i can crank the output balance full now, and still get a tiny boost when i kick in the effect.

the big thing is, once ya dial it in, being able to walk away...the truth is, these things are as much fun to tweak as they are to play thru!!

[R.G.]

i think r.g. was right, i think that r76 was a REAL late addition. here's the thing. replaced it with a 27k rather than the 33k just cuz it was what i had on hand. grounding one end of the 27 k resistor worked...until i soldered it in place! i tried to take the as yet uncut lead of the resistor that was going to the ground side and connect that to ground, and it made absolutlely no difference. i had to take the " hot" side of the resistor, literally directly off the "cold" side of the cap, and go directly to the same ground as the hi z jack. no more hum. so my question to you guys is this...how the hell can the input to the effect work if the audio path is being run directly to ground? it should be the same as turning down the volume on your guitar, right???

weird, or what?

that seems to me that "ground" is hot, and not at ground potential AT ALL. 

I think you're hot on the trail of what's wrong. At this point, you *know* that one of the "grounds" on the PCB is not connected to ground, right? When that happens to me, I get out my meter, set it to low ohms, and start probing all the ground points, because they all have to have zero ohms to each other right? And we know that the wiring in this thing is - well, less than the very best.

So if it were me, I'd hook my ohmmeter black wire to the ground of the input jack, then start probing ground locations on the wires of the board. They all have to connect, 100%, or it won't work well. I bet you find at least one wire that doesn't have good connections. Probe between the jack grounds, too.

A wire can well be broken inside the insulation. You're trying to verify whether the *wires* actually connect electrically, not by how they look.

[pinkjimiphoton]

thanks r.g., that is something i DID not know. i will do so later on indeed. and check the top board too, while i'm at it. it's only 6 screws, i have my notebook back with all my drawings, so i'm not as wussy about it as i was.

i suspect already the bad ground is gonna be ground point 23 on the fall board. that's the one that had broken on me.

but here's the thing...what the heck do i do if i check all the points, and everything comes up aces? do i start checking for continuity between all the wires from the fall board to the console board?

finally, should i use the continuity checker of my meter, or set it on the lowest resistance scale? does it matter? on my meter it shows a resistance if it's a few ohms, and also if there is voltage present.

thanks bro. peace.

[digi2t]

If I'm not mistaken, the grounding for the motherboard comes down from the console board. Black wire number 3, is jumpped from the transfo gnd (console points 1 and 4), and the black wire in the harness brings gnd down to the motherboard. Motherboard pad 10 is the gnd connection point being fed gnd from the console, then the gnd is distributed to pads 1, 13, 14, 22, and 23, which feed jack, switches, etc. down below.

Like R.G. said, multimeter continuity check time. Go through your grounds. We've got complete drawings now, so search and destroy bro.

[R.G.]

thanks r.g., that is something i DID not know. i will do so later on indeed. and check the top board too, while i'm at it. it's only 6 screws, i have my notebook back with all my drawings, so i'm not as wussy about it as i was.

With the experience you're gaining, you're learning that you can cope with more. That which does not kill us, and all that.

i suspect already the bad ground is gonna be ground point 23 on the fall board. that's the one that had broken on me.

Always good to look where there's been problems before!

but here's the thing...what the heck do i do if i check all the points, and everything comes up aces? do i start checking for continuity between all the wires from the fall board to the console board?

Yep. That's the thing about ground - all, completely, every one, 100% have to be connected. It's also possible that there is a crack in the traces on the PCB. Not a big deal, as that's what solder and wire is for. It's just a PITA to find where to solder. But the meter will tell you. If two places which are supposed to be ground are not connected, one or both of them have a wiring problem. And printed circuit traces are just that - wiring.

So  yes, test all the way up into the console board.

If the external wires check out, it just means that you're going to have to do the same thing, looking for ground connections, to each part that shows connection to ground on the schematic. Again, a PITA, but no big technical issue, just work.

finally, should i use the continuity checker of my meter, or set it on the lowest resistance scale? does it matter? on my meter it shows a resistance if it's a few ohms, and also if there is voltage present.

Do all your resistance testing with voltage off. And use the lowest ohms scale, as some continuity/beeper circuits detect continuity on low ohms. Finally, develop the habit of between every few tests touching your meter probes together to see if that still shows zero ohms. Some meters drift, too. Ask me how I found out about that one...    

If you find resistances over maybe 5 ohms between any two points, be very suspicious of that path. Below 5 ohms, it may be real or it may be your meter, as most common meters can't read low ohms very well.

[Keppy]

After 1 minute to stabilise, 46.0 vdc before R22, and exactly 34.0 vdc on the other side of R22.

Umm, you did want volts, and not amps? Just thought I'd check, since the measuring setup is different.

Yep, I wanted volts. Well, I wanted amps, but I framed it as the voltage across the 100 ohm resistor, which tells me a few other things at the same time.

Your circuit is pulling (46V - 34V)/100 ohms = 120ma, within the tolerance of the readings and resistor. That's more than I had thought it would, and it means I need to look at the power supply again.

How about just using a 48v supply? Mouser has many available, like this one:
http://www.mouser.com/ProductDetail/Phihong/PSAA20R-480-R/?qs=sGAEpiMZZMtpkqKkT5w3uiFtS68PTvw5CiLqbbUof8k%3d

or one of these:
http://www.mouser.com/Power/Plug-In-AC-Adapters/_/N-wp53?P=1z0wcnfZ1z0wd7tZ1z0k0c0Z1yztv3bZ1z0j9g6&Ns=Pricing%7C0

Jimi and Dino's units are seeing close to 48v at the Q6 collector anyway, so it seems like a 48v DC supply would be easiest, and only a few bucks more than the 24v AC supply you posted earlier.

If you still think a doubler is the way to go, the top two 24v AC adapters here are in stock at Mouser, cheap, and appear to have power to spare. No idea what kind of output cable they need, though, as they do not appear to have one...
http://www.mouser.com/Power/Plug-In-AC-Adapters/_/N-wp53?P=1z0wblf

[R.G.]

How about just using a 48v supply?

That'll probably be fine.
It's a switching type, so you may need to filter it more in case it makes whining noises in the audio. But it may not. Only one way to tell.

[Keppy]

How about just using a 48v supply?

That'll probably be fine.
It's a switching type, so you may need to filter it more in case it makes whining noises in the audio. But it may not. Only one way to tell.

You mean more than the filtering in the current Phase II circuit? i assumed the caps removing the AC ripple would be plenty for this. Am I (likely) wrong?

[pinkjimiphoton]

i bet it is a switching supply in the phase II as there's alot of background whining...it's faint, but there.

that said, i tried to match up the transistors, and find either them or equivalents. i had some luck, but not sure if i got them right...so you guys will have to check and see if
this stuff makes any sense, or is useful...if it is, cool, if not, i apologize for wasting time...been surfing all day in some cases trying to find parts.

here's what i came up with...the motorola part numbers i found in pdf's of ev products!!
these are the NTE equivalents i came up with...i may have made some mistakes. i found part #'s here where i could...

http://www.datasheetcatalog.com/catalog/p43040.shtml

the first number is as marked on the ludwig schematic...
the second is what the actual part is...to the best of my ability.
the third is the NTE equivalent...many can probably be found at mouser or allied for less tho.
finally, pdf's of each component so you much more knowledgable guys can see if the parts look right.
i really hope this helps!!!

if not, hey, i still learned something either way, so it's all good!!  

43045 = 2SC3206 = NTE399
http://www.nteinc.com/specs/300to399/pdf/nte399.pdf

43121= 2SC3298B = 2N2667 = NTE229
http://www.nteinc.com/specs/200to299/pdf/nte229.pdf

2n2546 = NTE2546
http://www.nteinc.com/specs/2500to2599/pdf/nte2545.pdf


43054 = 2SC3212A = NTE199
http://www.nteinc.com/specs/100to199/pdf/nte199.pdf

43173 = 2SC3330 = NTE2361
http://www.nteinc.com/specs/2300to2399/pdf/nte2361.pdf

43174 = 2SC3331 = NTE293
http://www.nteinc.com/specs/200to299/pdf/nte293.pdf

43175 = 2SC3332 = NTE460
http://www.nteinc.com/specs/400to499/pdf/nte460.pdf

43176 = 2SC3333 = NTE399
http://www.nteinc.com/specs/300to399/pdf/nte399.pdf

[pinkjimiphoton]

ooops...hit quote instead of modify!!! se4002 is also another number for the 43045 transistor...
http://www.nteinc.com/specs/100to199/pdf/nte123ap.pdf

i bet it is a switching supply in the phase II as there's alot of background whining...it's faint, but there.

that said, i tried to match up the transistors, and find either them or equivalents. i had some luck, but not sure if i got them right...so you guys will have to check and see if
this stuff makes any sense, or is useful...if it is, cool, if not, i apologize for wasting time...been surfing all day in some cases trying to find parts.

here's what i came up with...the motorola part numbers i found in pdf's of ev products!!
these are the NTE equivalents i came up with...i may have made some mistakes. i found part #'s here where i could...

http://www.datasheetcatalog.com/catalog/p43040.shtml

the first number is as marked on the ludwig schematic...
the second is what the actual part is...to the best of my ability.
the third is the NTE equivalent...many can probably be found at mouser or allied for less tho.
finally, pdf's of each component so you much more knowledgable guys can see if the parts look right.
i really hope this helps!!!

if not, hey, i still learned something either way, so it's all good!!  

43045 = 2SC3206 = SE4002 = NTE399
http://www.nteinc.com/specs/300to399/pdf/nte399.pdf

43121= 2SC3298B = 2N2667 = NTE229
http://www.nteinc.com/specs/200to299/pdf/nte229.pdf

2n2546 = NTE2546
http://www.nteinc.com/specs/2500to2599/pdf/nte2545.pdf


43054 = 2SC3212A = NTE199
http://www.nteinc.com/specs/100to199/pdf/nte199.pdf

43173 = 2SC3330 = NTE2361
http://www.nteinc.com/specs/2300to2399/pdf/nte2361.pdf

43174 = 2SC3331 = NTE293
http://www.nteinc.com/specs/200to299/pdf/nte293.pdf

43175 = 2SC3332 = NTE460
http://www.nteinc.com/specs/400to499/pdf/nte460.pdf

43176 = 2SC3333 = NTE399
http://www.nteinc.com/specs/300to399/pdf/nte399.pdf

[Keppy]

Those look like the same parts I proposed a few weeks ago, which R.G. deemed false matches. I'm inclined to believe him, both because of the logic he presented and because I later looked up a number attached to the diodes in the console board, which matched on that site to a transistor.

Here's the link to that post:
http://www.diystompboxes.com/smfforum/index.php?topic=91498.msg786053#msg786053

You say you found the matches in EV's literature, though? Do you have those links?

[pinkjimiphoton]

i found some here in this pdf:

http://www.pa-anlagen.ch/Manuals/Electro_Voice/Amplifiers/Service%2520Manual/EV%201244X%20Service%20Manual.pdf

[R.G.]

You mean more than the filtering in the current Phase II circuit? i assumed the caps removing the AC ripple would be plenty for this. Am I (likely) wrong?

Well, different filtering. The filtering on the DC supply in the P2 is intended specifically for 120Hz ripple, and so are the diodes. At high frequencies, electrolytic capacitors quit looking like capacitors and begin behaving like inductors. That's where all this business of bypassing electrolytic caps with small ceramic caps comes from.

At high frequencies, the diodes can't turn on and off fast enough, and can emit little squawks of RF trying to do so. However, it's possible that the existing regulator could be added to/fortified to make it small enough to be negligible. In either case, it would be interesting technical work. And it may work without it. I just don't know that, and can see some pitfalls based on past issues. It may be fine.

i bet it is a switching supply in the phase II as there's alot of background whining...it's faint, but there.

I suspect it's something else, perhaps the filters with a bit of oscillation. The power supply in the P2 is not a switching type according to the schematics.

that said, i tried to match up the transistors, and find either them or equivalents. i had some luck, but not sure if i got them right...so you guys will have to check and see if this stuff makes any sense, or is useful...if it is, cool, if not, i apologize for wasting time...been surfing all day in some cases trying to find parts.

I tried that, based on Keppy's earlier research. Once I'd hunted through to the end of the chain, the end device didn't look like what was actually on the board pictures, and did not match what I thought should be there based on the circuits. And on top of that, for the time when this thing was manufactured, EV and likely Ludwig would not have been using Japanese (2SC/2SA prefix) devices, and Moto would not have been making them. They'd be 2N prefixes.

Not that these could not work - it just seems unlikely. In the case of some of them, they're power devices in too-large plastic cases. The NTE261 *is* a nice one for Q6, based on the specifications, but we've already figured out that your Q6 is working fine.

Buying these from NTE will be quite expensive. I really think that 2N5551 at $0.04 each from Mouser will do most of it. It's a guess.

[pinkjimiphoton]

cool, just trying to find stuff.

thanks for the other info! :thu:

[Keppy]

At high frequencies, electrolytic capacitors quit looking like capacitors and begin behaving like inductors. That's where all this business of bypassing electrolytic caps with small ceramic caps comes from.

I assumed that was what C7 was for. Do I need to put another small value cap somewhere on the emitter side of Q6?

At high frequencies, the diodes can't turn on and off fast enough, and can emit little squawks of RF trying to do so.

I was only going to use the diodes (well, one of them) for the tiny voltage drop it would give me. Should I bypass them? I'm unclear as to the impact of RF on an audio signal/circuit, outside of the AM radio station I pick up when I'm breadboarding. 

Many circuits I've seen use a large/small cap arrangement to filter the power supply, with values similar to C7, C8, C11. The OCD, for example, uses nearly the same values in a 3-cap filter arrangement, except the small cap is 100nF instead of 10nF. What I'm trying to say is, the filtering on the Phase II is so similar to what I've seen on other high-gain circuits (in my tiny experience  ) that I'm not aware of what problems could arise in this design.

I feel a geofex article link coming on...