Hello I'm Joe and I have got to be doing something wrong . I have used every point to point diagram and while I finally got it to work the gain, tone, vol do nothing. I have a long and funny story behind this whole thing I won't bore you with , I am new to the diy "tube pedal" but 20 years ago I did build a little champ amp , so can someone maybe take a look at the pic an tell me what's going on. Thank you
Joe
(https://i.postimg.cc/WFzhqnf2/IMG-20230320-160513145.jpg) (https://postimg.cc/WFzhqnf2)
(https://i.postimg.cc/K3gjJY2w/IMG-20230320-160808141.jpg) (https://postimg.cc/K3gjJY2w)
So the voltages are
Pin 1/ 3.3
Pin 2/ -.676
Pin 3/ -.1
Pin 4/0
Pin 5/ 11.95
Pin 6/ 8.1
Pin 7/ -1.25
Pin 8 /0
Pin 9/ 5.85
Caps are
C1, 0.01uf
C2, 0.047uf
C3, 0.047uf
C4,. 560uf (closest to the 1uf it calls for what I had here)
Schematic?
I used this one for the tone gain and vol.
(https://i.postimg.cc/LYDrqc0W/Screenshot-20230320-145131.png) (https://postimg.cc/LYDrqc0W)
Not layout, schematic, your voltages seem wrong.
Welcome to the forum, Joeandamy! No worries, it's usually just a wiring error.
FYI, in case you need it, here is a tube pinout link - pins are read 'from below' with 9 being to the right, just to ensure we're on the same page.
https://www.evatco.com.au/tube-pin-out-configuration/ (https://www.evatco.com.au/tube-pin-out-configuration/)
Maybe you could walk thru the schematic here and ensure that this is the same thing? Tracing the wires on your build and so on. It's very hard to operate from 'pictures', and there's no real way to know if the 'Instructables' pic is correct! http://beavisaudio.com/projects/valvecaster/ (http://beavisaudio.com/projects/valvecaster/)
We'll get it going, just have to go thru the first steps to make sure everyone knows what's going on, and find out where you're at 'electronically'. If you built an amp kit, you can get this going with a little debugging, for sure!
Good morning and thanks for all the replies, so maybe a little back story, in 2000 before the Internet was so mainstream (still had dialup) I met a guy from NJ I was in Ohio on a forum we became phone friends and he took the time over the phone and we built a fender champ together over the phone for a few weeks and built it with a small tone stack , I was a tool maker and we traded some machine shop work for his help ,I built him a pickup winder and a few other thing. So fast forward to today I'm older in a better place in life so I wanted to build another but thought I would start with this tube pedal to get my feet wet. Well I'm sad to say I have right around 200.00 in this pedal and just bought a little bear g3 from eBay for 30.00 and they look to someone with little knowledge like almost the same circuit, so that's my funny story. Very much want to get this going and will post more findings after work and maybe with some help we can get this going ,kinda a big VH fan
Thanks everyone I really appreciate the help
(https://i.postimg.cc/BXDwBVqY/16794042325036046757067468018546.jpg) (https://postimg.cc/BXDwBVqY)
Hi Joe, whatever level of experience you're at, you're in the right place :) We enjoy discussing pedals, building tips, and all that, so no need to feel shy or anything ha ha. All these things are learning opportunities, for sure, so no worries.
- do you have and can you read a multimeter? Can you read a schematic?
- in the build pics, is that all of your 'creation', as in, not from a kit? (if so, nice work on the metal!) We'll have to get you to hand-trace where each wire is going, and confirm that each runs to where it should per the schematic (not the wiring diagram, that's a real pain and good to get used to schematics!)
Remember, the pins go clockwise when looking at the tube socket UNDERSIDE, and start at the notch :)
(https://i.postimg.cc/DmH7bQnQ/12-AU7-pinout.jpg) (https://postimg.cc/DmH7bQnQ)
And corresponds to:
1 plate B
2 grid B
3 cathode B
4 heater
5 heater
6 plate A
7 grid A
8 cathode A
9 Heater ctr tap
two things I can see from your build shot - you have mirrored some, but not all your connections. the middle pot is backwards. and there is a cap hanging off the footswitch which does not seem to be on the layout dia.
but yes, the circuit diagram please.
So yes I can read a multimeter and can read (ish) a schematic. So I did this from the layout not a schematic. The cap going to the switch is from pin 2 on the tube I seen a guy put his there and it seemed easier . The tone pot that is backwards was so the knobs all move the same direction. 1 thing to note as I was reading last Iam using 2, 100k pots and a 50k pot on the gain BUT the pots I have are all labeled with the letter b and I'm not sure if they are the right pots I will give a better run down after work of everything. When I was working on this I seen a guy posted his voltage numbers and my pin 1 was way off so I am running a 1meg and 2 470k resisters in series to get my pin 1 voltage to match his , I am running 12v
The problem is that WE can't work from the layout ;) And there's no way to verify if it works except for US to trace the thing vs. the schematic I linked to. Which is us doing the work for someone....y'know...we don't know 'what guy put the cap there', and from where to where...If it's C1, it is the input cap and SHOULD go to pin 2, FROM the input jack tip if wired correctly...
The pic doesn't say what values the resistors and such are, either. That is critically important to know in order to help, man...
Volume and tone pots should be "A", or log, taper pots. But don't concern yourself with that now, it will work with them, the controls will just feel bunched up on one end. Irrelevant to getting it working.
Pin1 is a plate, and should be as close to 12V as can be had. The R isn't there to drop voltage, lol, it sets the current the tube works at. 220k is what is listed; put it back that way. R3 should be 100k. Do not worry about matching anyone's voltages right now.
If you could go back to the link I provided to Beavis Audio...and match THEIR layout to the google one, make sure THEY match. That would be a great 1st step!
(they probably stole it from there anyway)
Then if they do match (and they may well), make sure your real-life build is the same, with the SAME parts values. There isn't much anyone can do til we can determine what we are working with, that the real build matches the google image matches the actual schematic...Where we're at, it is like trying to tell someone how to put a model together when they used unverified, unknown instructions. In another language we can't all speak, ha ha.
Basically - rebuild it to the diagram in Beavis, if you have to. It's verified, and documented. The google image is not - leave it. It's not a very hard circuit to unhouse, check vs. the known one and return it to 'stock'.
Avoid redoing the wires ON the stomp switch if you can; better to remove their OTHER ends and put them right. You could melt the terminals if you keep heating them. Hopefully the switch is wired correctly.
Don't get discouraged, just dig in and confirm the tube socket parts are on there right.
If you take a closeup pic of your stomp switch, and label the wires as to where they go, we'd be happy to see if the switch is wired correctly....After you have returned the tube socket to 'stock'!
The switch is a VERY common source of wiring errors, and also the jacks (which one is the 'tip' and 'sleeve', which are critical if you want to hear the circuit!)
Ok first thanks to everyone for getting me going on the right track with this , so I made the tube connections just like the beavisaudio except the cap on the switch, I can change it if needed but running out of room , this started life as a line 6 m5 I got from eBay (didn't work) but I wanted to keep the tube in the window but not locked down to that if that cap needs moved. So I replaced my "pull down" resister and replaced with 220k it's wired like the pic . Now GibsonGM you said something interesting, you said for the switch 1 pin is sleeve 1 pin is tip. That's not what I have both mine are tip I posted a pic of where all my wire are going with labels. My new voltage readings are
1) 6.79
2) -.008
3) .835
4) 0
5) 12.19
6) 7.88
7) -1.316
8&9) 0
Resisters used
R1:100k
R2:220k
R3:470k
R4:1M
Caps are
C1: 0.01uf
C2/C3: 0.047uf
C4: says 1uf closest I have is . 560 uf so that's in until Amazon shows up
For the lamp or led I just used a 12v light so no need for R5
Again thank you so much for the help
After putting things back like the pic I have no sound again but sounds like it's my switch like Gibsongm said
(https://i.postimg.cc/wyBsNgXG/IMG-20230321-145224893.jpg) (https://postimg.cc/wyBsNgXG)
(https://i.postimg.cc/6422Hc1V/IMG-20230321-145229783.jpg) (https://postimg.cc/6422Hc1V)
Is anyone else confused by the negative voltages? How is that possible?
I see at one stage you have voltage on pin 9, which is not connected. Then you had 0 volts. Did anything change?
I was trying to match some voltage I seen online and changed R2 to get the voltage , it is now as per beavisaudio
The voltage readings are done chassie ground as negative lead and then probe with positive. Should I ground on pin 4 or 8 and then check the voltage
Meter 'burping'....if the grid is grounded, it's probably just meter error showing 'negative' voltages...we hope, LOL.
The cap on the switch is fine, you can move it later if need be, let's get it working. Working now ONLY from the Beavis schematic/layout:
The pulldown is the 1Meg connected (somewhere) to the other end of the input cap on your switch and goes to ground, and should stay that way. It is R1, and is the 1 MEG. Remove 100k (check its value), needs to be 1 MEGOHM...
R2 is 220k, check. R3 is where the 100k goes! R4, 470, pin 7 to ground! Ground is the minus of your power supply.
When done, check each pot's GROUND connection. Check that the outside of your jacks also go to GROUND. The inner 'leg' parts of the jacks are the input and output TIPS, which go to the switch. As you make these checks/changes, you will get closer...
Pin 8 should be grounded YUP. "Far' side of gain pot must be, too!
Do you get any sound if you have the switch in BYPASS? If wired correctly (tips and the jumper to ground) - you should.
Is the footswitch pin numbering on the wiring diagram wrong?
(https://i.stack.imgur.com/1mfgT.gif)
I do get sound thru the bypass. On the strat if I strum hard as s#'t you can start to hear a faint sound . I will go check and complete the above list , thank you
Yes, be sure the switch is oriented correctly per Jim :) If you get any sound when engaged and it's wired right, you are starting to get on the right track.
Keep at it. Identify the part, and make sure each end is going where it should, then move to the next part. Make sure the heaters are wired correctly, too (power pin 5, ground pin 4).
Just for reference...it's best to solder parts to a tube socket WITHOUT the tube in, just in case. And don't use way too much solder, just a tad - no need to overflow and fill in the pin holes, ha ha....
WOW thank you so very much for helping me out everything work great tone , vol, and gain and sounds wonderful. I really appreciate everones help.
This is the new voltage numbers still a negative on pin 7
1)7.14
2)0
3).93
4)0
5)12.19
6)1.53
7)-1.12
8)0
9)5.74
I understand where I went wrong so leason learned I was using the pic on beavisaudio but printed off a parts list from another person , never checked if their "R1" was the same as beavisaudio "R1" .. crap or at least that's where I think I went wrong. I have wired this 6 times solder /de-solder for a week 😂😂😂😂😂
So I have a few follow-up question's lets say a pedal uses 1amp and you had a 5amp p/s could you run all 5 pedals from that in the same box? The reason I ask is I have 2 line 6 long boards that would make a great pedal board nice and neat. Also why are they running as a starve plate is it a safety issue or less noise from the DC or a combo of both. The 12v is nice you don't have to be near as careful ;D
Just a thought - if you're measuring voltage and don't have the black probe on 'really ground' but which is 'more positive', you might show a negative number at something like a grid, the cathode being elevated by that much. Not really sure what other case would result in a negative reading (?) If it's built right, hey...ain't broke, don't fix it :)
Almost no pedals would come anywhere near 1A! The VC probably uses about .16A at best, or 160mA. Less than 1/5 amp. If your PS can deliver 5A, in theory yes, you could run 5, 1A pedals from it, though. Nobody would want to come THAT close to the rating, so let's say 4. :)
Are you saying the Line 6 boards have their own power supply you want to use inside them? You could to that...Especially non-tube circuits, transistorized things tend to use way less current - the tube pulls .15A just at the heaters, which you don't have with opamp/transistor/jfet type circuits.
These little tube jobs run on starved plate for safety...easy introduction to tube circuits without high voltage...easy to find power supplies for the hobbyist....and when you run them at 'real' voltages like 300V, you need multiple stages to boost up and get real clipping, whereas you have much less headroom at a lower voltage, so they'll distort a lot easier. If you push the VC with a booster, you'll note that it breaks up very easily. If you ran the same thing at 300V, you would have much less distortion!
(http://beavisaudio.com/projects/valvecaster/img/MatsuminValveCaster.gif)
Isn't the grid leak circuit here supposed to generate a negative grid voltage? I thought it depends on doing so.
Negative voltage "As referenced from...?"
Isn't the grid just "1.12 volts more negative than the cathode"? If the neg probe were put on cathode, wouldn't you read exactly that?
If you measured the cathode, wouldn't you find it to be 1.12 volts more POSITIVE than the grid?
The negative voltage on the grid is called contact potential and it arises because the cathode emits electrons just from being heated. Some electrons are intercepted by the grid, which goes negative as a result.
In the standard 5-tube AC-DC radios which were built in the hundreds of millions between 1938 and 1970, a 10 megohm resistor from grid to ground of a 12AV6 triode + double diode gave enough negative bias to allow the input signal to take detector-level outputs and amplify them in the linear range. Since the detector output was negative, the tube remained in the linear region and never pulled grid current. If the radio had a phono input, this went through a capacitor to the volume control then a grid capacitor and the bias was still provided by the 10 megohm resistor. In this case, the input went negative and positive but usually never went positive enough to draw grid current. In these sets, the cathode was grounded with no cathode resistor.
BTW the triode section of the 12AV6 is identical to the triode section in a 12AX7. Same ratings and performance.
Thanks for that 'missing piece', Ron, the physical reason we get the grid more negative than the cathode. I've always looked at it or seen it described from the cathode side, 'making the cathode x volts more positive' when setting up bias. Apparently it is a real 'thing', as referenced from ground. Funny, I've never even looked!
If the cathode is 0v and the grid is 0v, the triode is just a diode. Allowing the grid to charge negative with respect to the cathode moves it toward cutoff for linear operation. I think this only happens with low voltage "starved plate" conditions.
http://valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf
If you read Merlins paper, you may get a surprise when the penny drops that the grid current produced lowers the grid input resistance - quite a bit. The grid resistor is not defining the input impedance at all.
Sure - grid current limiting, abrupt loss of input impedance. You can have this condition at any voltage, AFAIK.
The way I was viewing the grid voltage (rather, not viewing it!) comes from P 15 of Merlin's "Designing Valve Preamps For Guitar and Bass", "...we are only trying to make the grid more negative than the cathode, which is exactly the same thing as making the cathode more positive than the grid."
Anytime I mess w/tubes, I am only thinking about what cathode resistor I choose, and why. It works. After doing the math and playing w/load lines, I've never actually measured the damn thing! :)
Lo and behold, there it is. Should've been intuitive, but I work this stuff like a shade tree mechanic.
Well, I wonder what it does to a guitar output into the Valvecaster if the input impedance goes south of 100k (Merlin cites 20k in one condition). At 100Hz the Xc of the 47nF is around 34k and obviously drops above that. Nevertheless, folks are happy with the sound. I've breadboarded one and like it - one day I'll get a round tuit.
My version, didn't want the pot on the cathode, probably would be scratchy.
(https://i.postimg.cc/9Ry7WxcG/Mozzcaster.jpg) (https://postimg.cc/9Ry7WxcG)
It might be a 'stupid question, but I was thinking about 'actually have negative voltage at the grid', and it's not trivial at over -1V...how come tube amps with no input cap don't cause guitar pots to make scratching noises? I guess I always considered the voltage there to be academic...somehow internal (lol)...but no...
The VC is a fun circuit to be sure, esp. if you are using it as a boost!