Aldrin (Lunar Module) to Screw Driver transformation

[Chuck D. Bones]

You don't need to reinstall the caps to make the voltage measurement on R6.

What's the value of R1 & R2?

That soldering on R14 & R15 is horrible. I sure hope that pedal didn't come from Skreddy like that.

Reinstalling ceramic SMD caps is risky. They are easily damaged by the heat of soldering. They don't always fail right away. The thermal stress can cause microcracks, which leads to failure later on. I highly recommend getting new caps and when you solder them, don't touch the tip of the iron to the caps. If you have a hot air pencil, use that.

I'll update my schematic. Looks like a few ref des changed.

It's not surprising that Skreddy had problems with Ge transistors. Good ones are hard to come by and when you build thousands of pedals, warranty returns could be a real problem.

One more thing, can we get photos of the front panel and the serial number? Thnx

 

[MattG]

One more thing, can we get photos of the front panel and the serial number? Thnx

Sure… but what do you mean by “front panel”?

 

[Chuck D. Bones]

Does it look like this? If yes, then I don't need a pic.

 

[MattG]

It does look like that, but for completeness, I'll post anyway!

I added R1 and R2 to the original post. R1 is 2k. R2 is not labeled, will it be sufficient to measure voltage drop across it when powered up?

Thanks for the tips on the ceramic SMD caps! I got a heat pen a while ago for doing SMD work, but I haven't had a chance to use it, now I finally have a reason!

Edit: just measured across R6 and R2 while powered up from battery. Battery reads 9.6v. I get zero volts across both resistors (well, 0.02mV across R6)?

Let me know if I can get any more pics or info for you!

 

[Chuck D. Bones]

Verify C8 is 10uF. Recheck C6; 180pF seems too small. You can measure the resistance of R2 while it's on the board. Power off, + lead of the DMM to the side closest to Q1 .Wait for the reading to settle as C3 charges up. Zero volts across R6 is wrong, try it again. If you're using a battery for power, you have to plug a cable into the IN jack to get power to the board.

 

[MattG]

Verify C8 is 10uF. Recheck C6; 180pF seems too small. You can measure the resistance of R2 while it's on the board. Power off, + lead of the DMM to the side closest to Q1 .Wait for the reading to settle as C3 charges up. Zero volts across R6 is wrong, try it again. If you're using a battery for power, you have to plug a cable into the IN jack to get power to the board.

R2 - 1.5k

I re-checked C6, I'm getting 141 pF now.

C8 measured 8.5uF, which is within 20% of 10uF.

I measure 1.8v across R6, does that seem reasonable? (I have to press really hard with the probes on either side of R6 to get a nonzero reading.)

 

[Chuck D. Bones]

That makes sense. Except for C6. I believe your measurement, but at 150pF C6 is too small to do anything audible. It's possible that C6 was damaged when it was desoldered.

1.8V across R6 implies that R6 = 22K.

 

[Chuck D. Bones]

Here's the schematic based on Matt's photos, measurements and research.

 

[fig]

Is this the tone stage?

 

[Chuck D. Bones]