@billy
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Are your LEDs standard or bi colour it’s difficult to see if they’re standard 2 pin LEDs the cathode (minus ) needs to go into the pad without the white box and anode + to the centre pad
The circuit won’t work without D1 functioning it’s part of the LFO
Excellent set up
I’ve got a question Barry
The fender twin pro tube I’ve got, how’s the hum on yours
Obviously you’d expect some on a 100w job mine isn’t bad I’m just trying to gauge it compared to other tube amps I’ve used and I’d say it’s more noticeable
Great looking builds Chuck
I’ve got a few lying around I may try out your ideas I love the versatility of this circuit and how you can go from crunch to a nice jangley tone
I remember Wilkie did a Marshall jubilee mod with the zenith pro board so there’s plenty of possibilities for unique tone
Barry beat me to it
Anyway
All components look to be the correct value and orientation
The only other thing I’d mention as a quick check is make sure you have the 3906 PNP transistor in Q2
Could just be an audio wire running too close to a power wire Drew
Do the old pencil test get either a pencil or something non conductive and wiggle your wires to see if it affects the noise
Try to place your audio carrying wires as far away as you can from power wires if they have to cross do it like this + not paralell like this =
Does it make the noise when battery powered
Without knowing what it is hard to say Drew
Could be a filter cap not filtering out rf noise or poor shielding is it back in it’s box?
There’s a few things internal and external that can cause noise
Did you reflow any capacitor joints
You’d need something fairly large like the 220n
That cap will affect the bass and mids strictly speaking any capacitor will work a larger value will allow more lows and smaller more highs
You could add capacitors in parallel e.g. two 100n would give you 200n
It doesn’t look great though but if you can’t wait it’ll be pretty close
Remember capacitors have a tolerance rating so you may get a coupla 100nfs a little over
If I use paralell caps I usually cut one caps legs short, leave the other long twist and solder them together near the top of the legs
Q1 seems to be your main problem area
What voltages do you get on the empty socket of Q1
I notice you’ve soldered Q2 and 3 into their sockets? Q1 socket looks different
Do you have a DC jack wired or is it just the battery
Probe the +9v and Gnd pads on the pcb what voltage are you getting there, is it still 6.6v
This is how I’d normally use the schematic to try and highlight where my problem might be yours appears to be working if you have 6.6v going in and your VB is half that, which is correct with your VB points being 3.3v that tells us your voltage divider is working albeit not exactly the voltage we want but still half your power supply, your VC is correct with 4.95v at Q2 collector, so it appears VA just isn’t getting to Q1 drain so I’d check your VA point above R29 and Q1 drain out of socket where you should be getting whatever voltage is going into the pcb
With your meter impedance it’s not absolutely critical as long as you take it into account
Some info here from Tonmann on the old site
https://guitarpcb.webs.com/apps/forums/topics/show/12988309-troubleshooting-opamp-circuits
Well worth a read as it also outlines troubleshooting op amp circuits
You don’t put them on the underside would be my understanding
The suggestion is you put them as shown in the photo the reference to sides would be the switch, on one side of it D5 and 6 switched to the other side D1, 2, 3 and 4
You should find your meter impedance from the make and model basically you want a 10M ohm impedance for accurate readings
BIAS: Controls the filter resonance frequency. When Sensitivity is turned fully off the Bias can be used as a sweepable filter.
There’s some information here on the old site which runs through the circuit with the block diagram (below)
https://guitarpcb.webs.com/<wbr />apps/forums/topics/show/<wbr />8230458-swah-super-white
If you click on a link that doesn’t work just add .webs to the url eg guitarpcb.webs.com
I wouldn’t give up with this pcb you can always bypass traces if pads are lifted by connecting components directly with jumpers as you have with Q1 the pads are also double sided so you can solder component side also if needed
I’ve had a quick look I’m at work at the moment
All your values that I can see look correct can’t see all of what makes up R27 or the majority of the capacitors or TR1 value which should be a 503 code
Your voltages are off the voltage designations are
VA 9v
VB half power supply around 4.5v
VC 5v
We can see IC3 works with Q2/3 collectors at 4.95v so VC is ok
I’d check your power circuit first check what voltage you get on the 9v pad then through D4 the anode should be power supply then a little less at the cathode side then follow the schematic to the junction of R29 and 30 the voltage divider which should be half of your power supply (below) as you say Q1 drain voltage is way off hence why I’d start at the power supply circuit to see if your problem begins here, Q1 drain you’re looking for power supply less the voltage dropped through D4 around 0.7 to 1v
Here’s what your voltages should be around
Proper Q voltages for comparison (all pots full CCW)
Q1: (7.27 – 3.71 – 3.23 – DSG) Drain Source Gate not CBE
Q2: (5.05 – 3.75 – 2.90 – CBE)
Q3: (5.05 – 2.90 – 2.86 – CBE)
What is the input impedance of your meter that would let us know the accuracy of your meter readings
Getting wrapped up in the old days haha
I actually came to comment on your build which I like I wouldn’t change those knobs I think they give it a great look
That’s one of Pete’s, just showing one of his builds
Pete used to document a lot with his builds and ideas you may find some very useful stuff in his photo gallery on the old site
https://guitarpcb.webs.com/apps/photos/album?albumid=14577966
