SOLVED DOD-FX59 Thrashmaster repair

[fancypete]

This is my first post on this forum and I want to start by saying how cool this community is. I'm brand new to building guitar pedals and am excited to get into this cool hobby. Demystifying these devices that have intrigued me for years has been very gratifying! That said, I was wondering if anyone could help me with a repair question.

I have a DOD-FX59 Thrashmaster that has the usual DOD issues. The tactile switch works intermittently of course, and I plan to replace it. The effect works fine when it's on, but the mystery happens when the pedal is bypassed. At first the clean guitar sound is ok, but over the course of about 30 seconds the volume starts to decrease until it is very quiet. I could just keep the effect on all the time and use an external pedal to switch it on and off, but that's no fun and takes up space.

Any ideas what could be going on? I was thinking of replacing all the electrolytic caps, but really that's just a guess. What seems odd to me is that it doesn't drop in volume when the effect is on, only when bypassed.

Anyhow, thanks for any ideas you guys have!

 

[Chuck D. Bones]

How old is this pedal? Aluminum electrolytics do go bad after a number of years, but that's not the only possible cause. Is there any sign of corrosion on the board? Has this pedal been modded or repaired in the past?

Take a look at other posts in this forum. The usual protocol is to post hi-res pics so we can see what's going on.

 

[fancypete]

Thanks for the reply. Doesn't look like any mods have been done, short of a hack job on the 9v snap (I'm definitely replacing it). Looks decently clean inside to me.

I'll post some pics.

 

[fancypete]

 

[fancypete]

 

[Chuck D. Bones]

I suspect C28 is the culprit. It's the black electrolytic near the center of the board. Switches do wear out or the contacts tarnish, so replacing S1 is a good idea. Check the mechanical alignment to make sure the stomp pad is fully actuating the switch.

 

[poltow]

fancypete
I have the same pedal. I need to fix it. Do you mind taking a few more pictures so I can see all the connections and try to re solder mine? I'd really appreciate it!!! Thanks!!!

 

[Barry]

http://files.effectsdatabase.com/docs/schematics/dod_fx59.gif

This Schematic might help

 

[fancypete]

I'll post some more pics asap, I'm not home until tonight though.

Also, regarding the schematic, I've read that there are some errors in it. Although I haven't verified that myself. Apparently DOD wasn't very consistent with their documentation. Maybe someone who is savvy with this sort of thing can analyze the diagram and confirm.

 

[fancypete]

 

[fancypete]

Not sure if these pics will help you but here they are!

Just got some tact switches in the mail. Will solder it up and post results soon.

 

[fancypete]

OK, I removed the old switch. I tested it with my multimeter and it was faulty. I installed the new one I got from Tayda (A-5153), and voila. Pedal works great! I hope this helps somebody in the future who encounters a similar issue. I may still replace some of the caps, but in the meantime I'm happy.