SOLVED War Scythe (tonebender part) volume/input issues

[kcrimson13]

Hi everyone, first post here. I was wondering if anyone could help me troubleshoot the tonebender part of my warscythe build. Both the octave and the big muff part of the pedal work perfectly fine.

The issue with the tonebender was identified as a perceived volume drop when circuit was engaged (all knobs at noon is less than unity). All the knobs apper to work (tone is more bassey on max, more trebly on minimum/ fuzz increases fuzz/ level affects volume).
After many attempts to debug without success (I don't think i've fried the germanium transistor while soldering), I built an audio probe, which quickly revealed what I now think is the issue. When tonebender is engaged, the input signal directly from the guitar is not clean, and has less volume than when circuit is bypassed. Rotating any of the knobs doesn't change this signal. I am at a loss at what could be causing this. Anyone has any suggestions/ideas on how to proceed from here?

Thank you for reading!

 

[okstateblues]

Good clear pictures will help the group if you would post some of both sides of the board for diagnosing.

 

[kcrimson13]

Of course. I added a dpdt switch on the muff side lifts both diodes and replaced the octave diodes with schottky (those are the only mods from the original schematic )

 

[kcrimson13]

the last 2 photos are the tonebender circuit - the only part that isn't working as supposed to :S

 

[Chuck D. Bones]

Q2 is leakage biased. Not all transistors work well in this circuit. With power on and no signal, measure the voltage on Q2's collector. What part # did you use for Q2 and where did you get it?

 

[kcrimson13]

for Q2 i used the 2N404 provided with my musikding kit. Okay, I'm new to measuring transistors, but with the 9V power supply in the circuit and the tonebender switched on I checked the terminals of the Q2 transistor with a digital multimeter set to diode mode:

Base to Collector - 0.214V in one direction, infinite in the other;
Base to Emitter - 0.216V in one direction, infinite in the other;
Emitter to collector - 0.700V in one direction, infinite in the other (is this normal?)

Were these the measurements you wanted?

 

[Chuck D. Bones]

First of all, 2N404 is a PNP transistor and will not work for Q2, wrong polarity. You need an NPN germanium transistor and like I said earlier, not all Ge transistors will work in this pedal so use a socket for Q2.

Tell us every part you used that does not match the BOM. I can tell by looking that Q4 and Q5 are neither 2N1308 or MPSA13. We're here to help, please make our job easier.

Here's how to measure Q2's collector voltage: Set your DMM to measure voltage, 20V scale. Connect black lead to ground on one of the jacks. Connect the red lead to Q2 collector. Apply power. Does not matter if the TB is enabled or not, the readings will be the same. No point in making this measurement until you have the right polarity transistor installed.

 

[kcrimson13]

Hi, thank you very very much for fast reply.

I bought the kit from musikding, and I told the changes that I did - I hadn't thought that the material provided would be different than pedalpcb's BOM - stupid of me xD.

These are all of the transistors used (also the red LEDs in the clipping section are not 3mm)
Q1 - MPSA18
Q2 -2N404
Q3 - 2N3904
Q4 - BC107A
Q5 - BC107A
Q6 - 2N3904
Q7 - 2N5089
Q8 - 2N3906
Q9 - 2N5089

So, Q2 is definitely not going to work since its not the right polarity - thanks for pointing that out and for teaching me how to measure transistor voltage! Is there a problem with Q4 or Q5 (even though the muff side works good)? Do you think this could be the cause of my issue (I mean - should I update the title to include SOLVED)?

 

[Chuck D. Bones]

Q4 & Q5 will work, the muff is pretty forgiving for transistors. They are NOT what EQD puts in their pedal. Q2 is completely wrong. I guess you can't trust these "kits." Gotta verify every component against the BOM and then try to figure out if the parts that don't match will still work.

Do you know where to get a good transistor for Q2? What country are you in?

Save that 2N404, it will be useful in something else. Assuming it's a real 2N404.

Fingers crossed, but let's wait until your pedal is up & running before we mark it SOLVED.

 

[kcrimson13]

I am in Portugal - most eletronics stores around me don't carry germanium transistors I think (they don't stock germanium diodes, or at least I could not find any). I will try to contact kit supplier or maybe even order some online. I will do what you said about socketing transistors (Q2 Q4 and Q5) and trying different ones to see if I hear any audible differences. And next time I will definitely check the BOM, for this mistake has cost me many sleepless nights!

Once again thank you If it doesn't work after the transistor swap now I know where to troubleshoot.

 

[Chuck D. Bones]

Be very careful about ordering transistors online. Many unscrupulous sellers out there.

 

[music6000]

Contact Hector at Retroamplis in Spain, He should be able to help you,
I have purchased twice from him for Klon Panasonic capacitors, I'm in Australia!

https://www.retroamplis.com/epages/...Products&SearchString=germanium&SearchButton=