Build Your Own Clone Message Board

Hi guys,
Have no effect when powering my new build and would appreciate your help. Have bypass and LED comes on when engaged. Checked a few other posts related to this pedal and checked some voltages:

IC1
(1) 8.7, (2) 5.9, (3) 8.7, (4) 0, (5) 0, (6) 4.1, (7) 8.3, (8) 9.2

IC2
(1) 9.2, (2) 0, (3) 0, (4) 0, (5) 0, (6) 4.1, (7) 4.1 (8) 9.2

Some weird results, I know.

Top R13/R14: 4.12
Bottom R14: 2.83
Top R15: 2.83
Top R2: 2.12
Bottom R2: 2.83

Q1 (L to R) 9.2, 2.1, 4.3

Got these same results both before and after retouching solder points. Here's some pics:











Thanks in advance.

Pins 1 (outputs) of the the two op-amps should be at about the same as Vref. Vref on pins 6 is 4.1 (for both amps) so that is as it should be. The outputs of the two op-amps are hard positive. This is not right considering that the inverting input of one is also quite hard positive while the inverting input of the second is at Vref. Since the inverting inputs and the outputs are both eventually AC coupled through capacitors, as far as I can see both inputs and outputs should sit at Vref. Maybe there is a short around IC1 or the IC is dead. looking at your pics it looks like there is some junk floating around on the back of the PCB that might be causing a short.

I can't see if you socketed the ICs. If you did, unplug them and then measure the voltages on pins 7 and 1 of both op-amps. With the ICs removed you should have 0 volts on these pins. If you don't, measure back away from those pins to see which components have a voltage on them and you may be able to trace which component is shorted across to DC. None of the resistors associated with the op-amps should have any DC on them (with the op-amps removed) as far as I can see.

Good advice from Tark - also, check that the chips are oriented correctly: pin 1 on the top chip is oriented toward the top and the lower chip's pin 1 should be at the bottom.

Hi guys,
Thanks for the input. ICs are socketed and oriented correctly, IC1 pin 1 at top and IC2 pin 1 at bottom. Checked voltages per Tark and both pin 1 and 7 for IC1 are reading a couple 10ths of a volt and slowly dropping. Followed path and measured at 470 and 15k resistors and am getting same couple tenths and dropping. Followed IC 1 up to the Volume Pot. IC2 pin 1 and pin 7 are measuring essentially 0V. Checked at the 470, 10k, 33k and 8k2 resistors and both treble and bass pots for IC2 and also getting 0V. Is this what you were looking for? Anything else you guys suggest?

Zero volts on pins 1 and 7 of both amps (with op-amps removed) is what you should see. The voltages, as you say, may take a little while to settle as the charge on the various capacitors stabilises. It is worth checking the other pins - pins 8 +9 - pins 3,4 & 5 all zero. if that is the case it would seem to me that you have maybe one and possibly two damaged op-amps.

Thanks again Tark. Here's other pin readings with the ICs removed:
IC1: (3)-(5) all at 0, (6) @ 4.6V, (8) @ 9.2V
IC2: same - (3)-(5) all at 0, (6) @ 4.6V, (8) @ 9.2V

Well that all seems as it should be. I hate to say it but I think you have two damaged op-amps. Were you perhaps working in static prone conditions? very low humidity and or central heating / synthetic carpets and or clothing?

Did you perhaps, as has been suggested in the DIY section, organise all your parts by sticking them into a piece of polystyrene foam (not a good idea for many ICs and semiconductors which can be damaged by the very high voltages that can accumulate on such foam).

Thanks Tark. Well it is winter in Chicago so the heat's on - humidifier too, though. Work area is hardwood floors. ICs only "stored" stuck in the foam strips as they came with the kit. Guess I'll look up some replacements.

Well that sounds like the chances of static damage were reasonably low. Unfortunately in some ways the easiest path is to obtain 2 replacement chips and try them in the pedal. However if that does not work it is going to be a bit annoying

If I'm not mistaken there have been a few instances of bad op-amps being shipped with this kit. The thing to do is use a signal probe to see if it's one or both chips that are at fault.

Hi Stephen, I know just enough about circuits and schematics to be dangerous. Got the signal tester out and I'm only getting signal on IC1 at pins 1, 2 and 7 and on IC2 - nowhere. I swapped the ICs around (I remembered to make sure they were oriented correctly) and get no signal at any pin for either IC.

Then it would seem that the IC that was originally in the IC2 socket before you started, is dead.

Got the replacements in the mail today, popped them in, and it works great. Don't know if it was Mike Marsh or Duhvoodooman who said it earlier, but it does play really nice with the Champlifier to add some sparkle. Thanks everyone.

Cool! It was in fact DVM, I just agreed - sounds GREAT with the Champlifier!