Build Your Own Clone Message Board

I tested the OD2 with the battery and it worked fine. After testing with the adapter the MOSFET build Boost no longer worked. I noticed that a small piece of copper wire from the BOOST OUT (pin 7) made contact with 4K7 resistor. As a result I had 9 V on the BOOST OUT circuit.

The OD and both leds still work. After switching to BOOST I get silence. Any ideas which components I need to replace ?

Thanks for your suggestions...

Paul

Following the boost output backwards into the boost circuit, the first sensitive component that the +9VDC would hit would be the 10uf electrolytic cap up near the boost level pot lug connections. It would be entering the cap in the wrong direction of polarity and could potentially blow the cap. The next polar component it would hit would be the drain leg of the BS170 MOSFET, but that already has significant positive voltage on it. Since the MOSFET boost is rated for 18V operation, I doubt that would be a problem. So that electrolytic cap would be my best guess. Did you hear a "pop" when it happened, or is there any visible deformation of the cap or leakage of material from it?

Another thing to be *sure* to check is that the output of the adapter is DC, not AC. If it's AC don't use it again!

Also, do you smell anything that smells like it got burnt up (ozone)? There's a trick you can do with a small drinking straw where you can get a more accurate detection of a burnt component. It sounds silly, I know, putting a straw up to your nose and all, but it does work - lol. Just don't use the straw to sniff anything else.

Thanks for your suggestions!

I used a one spot adapter, so no AC but a lot of mA's (which was not such a good idea for testing). I did smell the ozone, it seemed to come fom the pot. But that measured ok. I'll check it further with the straw (good idea).

I replaced the e-cap with no success.

The current rating of the Power Supply isn't a factor. It simply tells you how much current it can provide if asked to do so. If the pedal only requires a few milliamps of current that's all the PS will provide. The PS could be rated at 100 amps but if the load only requires 5ma nothing will be damaged by the PS.

I'm beginning to suspect that the power supply had nothing to do with the failure - it was coincidental to a failed solder connection, perhaps? Can we see some pictures?

Do you have a DMM available to check the function of the two diodes in the MOSFET boost stage, and to get DC voltage readings off the legs of the MOSFET?

Yes, diodes ok, MOSFET legs, s: 0.4 V, g: 2.2 V, d: 4.5 V, battery 8.7 V

That all looks normal. With the boost footswitch engaged, to you have continuity between lugs 7 & 8?

Thanks, yes i have continuity.

I bought a new dmm and checked the circuit again. It seems I have a problem with the A100K pot. I measure 100 k between 1 and 3 and nothing on 2. So i think this is my problem.

Thanks for your help and suggestions.

Paul

Was the pot turned fully CCW when you measured it? If so then your zero ohm measurement is normal. When a pot is turned fully CCW lugs 1&2 are shorted together. When you turn it fully CW lugs 2&3 are shorted together.

Yes I tried various settings. I have tested the boost circuit with 2 and 3 externally shorted and then I get a boosted signal...