Weird voltage problem.

[wilcorocks]

I built two sunkings this week, both worked great when tested out.  After I boxed both and sent them to my buddies, they both came back with funky popping sounds.  After looking through it, I went to test voltages on the ic's and got no readings.  I went to the power supply and found that it was only pulling .231 volts!  What could have caused this?  I think my brain is fried because I can get my head around it.

Thanks.

[jkokura]

Have you tried new charge pumps? It's possible they got blown if fed too high a voltage. Did your friends tell you how the problems started for them? It's weird that it happened for both of them.

Jacob

[wilcorocks]

Tried all new IC's.  No dice... It powers up for a second (5 volts) then rapidly drops voltage draw and starts thumping.  Strange thing is it works with a battery!  I don't know what to make of it.  Can't read the pins because voltage never makes it there.

[wilcorocks]

New update...

Played it with a battery for a bit... After about 1 minute I started to smell something... Felt the 7660spca and it was super hot.  Looked around and found no solder bridges.  What could it mean?

[jkokura]

Check for continuity between power and ground. If your power is going to ground you could experience that problem. Without more data I can't say for sure.

Jacob

[wilcorocks]

Thanks Jacob,


Without sounding like a total idiot, how would I check for continuity between power and ground (I know how to get my multi on the setting, just don't know where to look in the pedal).

[madbean]

Post some pics if you can. In my experience, a hot IC means it is in backwards, Not always, but sometimes.

[jkokura]

Good suggestion Brian.

Put one lead on ground and one on power. If the multimeter beeps, that means they're connected.

Jacob

[wilcorocks]

Here are links to a few pics.

http://i1130.photobucket.com/albums/m522/wilcorocks/IMG_0533.jpg

http://i1130.photobucket.com/albums/m522/wilcorocks/IMG_0532.jpg

http://i1130.photobucket.com/albums/m522/wilcorocks/IMG_0527.jpg

http://i1130.photobucket.com/albums/m522/wilcorocks/IMG_0524.jpg

Sorry, don't know how to embed from a website yet.

Josh

Oh, All IC's were in the proper way.  Looking for continuity to ground now.

[wilcorocks]

The only places I found continuity on the board that I was confused about was the back end of D3 Pin 3 (Should go to ground my miss) of IC 3 Pin 4 of IC 1 but not IC 2.  Did I miss something?

[wilcorocks]

Changed the ICs for a third time... it worked.  Just played it for 30 min and no problems... I'm guessing that they plugged into a 18 volt outlet, followed by my ability to pull out an IC and put it right back in and think I changed it.

Thanks guys.

[madbean]

Plugging an 18v into it could have burned up the Zener protection diode or the charge pump. The TC1044/ICL7660 can accept up to 10v. Beyond that it won't work...and could be damaged. The Zener diode protection is actually a little over-rated...it's 12v, I think.

However, I've heard that those pumps can take 12v without a problem. FrequencyCentral, who designs a lot of sub-mini tube amps, uses a 12v input on a charge pump and then bumps it up to 70v for his tubes.

I'm pretty sure this is why Finnegan uses the weirdo DC plug on the Klon....so that you can only use his supplied wall wart and not plug in 18v to the thing and destroy it.

[wilcorocks]

Yeah,

I actually replaced the zener as well, but I did that first and after testing it was still not pulling power, I'm thinking the 7660 may have been blown since it heated up so quickly.  The new one stays nice and cool.

Thanks again!