DC effects loop mod

[Gerax]

Resurrecting the thread. Still the same situation (man, it's been years I haven't touched open that amp...) but I really need to understand how to convert the FX loop to serial, as I'm going to use two DC3s in a rack project with a switching system for pedals and preamps and a line mixer for effects. All in stereo (so I need to mod both amps).
Anybody can help? Picture of the amp is the one right above.
Thanks

 

[Monsta-Tone]

PM me with an email address
I’ll send you the drawing

 

[Gerax]

I never found a complete how-to for this and had to figure it out for myself, so here's the deal...

At first, I just removed the white wire from the pot and bridged the other two terminals of the pot with a jumper wire. But, as others have described, this caused the amp to go silent if the loop wasn't in use. If this is all you do for the mod, then you have to use a cable to patch the send and return jacks together. The solution is to move the bare wire that comes from the positive "no-plug-inserted" side of the return jack so that it connects to the positive terminal of the send jack.

So here's the complete how-to for the FX loop mod:

1. Remove the white wire that goes to the mix pot and tape it off. This wire seems to connect back to the FX send positive terminal, but it goes through the circuit board in-between for some reason.
2. If you're leaving the mix pot in place, just put a jumper wire between the orange wire and the pink/red wire on the pot to effectively bypass the pot. If you're removing the pot, connect the orange wire and the pink/red wire. The red/pink wire is the positive lead from the FX return jack (from the side of the jack that's active when something is plugged into the jack). The orange wire goes to the power amp.
3. At least on my early 1991-ish DC-5, there's a bare wire coming from the FX return jack that normally meets up with the orange wire at the mix pot's middle terminal. Move this wire to the positive terminal of the send pot. This wire is the alternative route of the FX return when there's nothing plugged into the jack. When there is no plug in the return jack, the jack bridges that no-plug-inserted positive terminal to the plug-inserted positive terminal (which is where the pink/red wire is). So when no plug is inserted, you now have a circuit connecting the send positive terminal to the pink/red wire, which connects to the orange wire, which goes to the power amp. So we now have a proper bridge between send and return for when nothing is plugged into the loop. No patch cable required.

Enjoy.

Hi, do you think your procedure is going to work on my DC3?, A pic of the current status of the loop is just under your last post.
Thank you.

L.

 

[Monsta-Tone]

Works really well on all DC’s

 

[Gatroe]

Bumping this thread to see if anyone has a drawing for this mod. My DC-5 had the effects loop disconnected when I purchased it and I have different color wires that the ones pictured in here. Thanks!

 

[jpistolas]

I hope Monsta-Tone doesn't mind me posting his illustration of the mod but here is the one I saved & used to convert my DC-5 to serial. I hope this helps.

 

[Gatroe]

Finally have some time to dig in. Does anyone have a picture after they completed the mod? This is how my amps FX loop is currently set up.

 

[Gatroe]

Finally have some time to dig in. Does anyone have a picture after they completed the mod? This is how my amps FX loop is currently set up.

Tried this as a temporary setup. While I got signal without anything in the loop, when I connected a delay, it did work but the delay repeats were very low even with the mix all the way up. Threw the delay in front of the amp and got the correct repeats and sound that I would like to have from the loop.

 

[Gatroe]

Ended up figuring this out this weekend and thought I’d provide some pictures after completing the mod.

I soldered together the red from the return jack, the orange from the board and in this picture, the grey wire from the switch terminal of the send jack. It might be a bare wire for some people but I didn’t have one so I swapped it for a piece of wire I had sitting around. Disconnected and capped off the short white wire that went to the pot.

Works and sounds great. Thanks to anyone who reached out with paperwork and schematics.

 

[Kstarrguitar]

Ended up figuring this out this weekend and thought I’d provide some pictures after completing the mod.

I soldered together the red from the return jack, the orange from the board and in this picture, the grey wire from the switch terminal of the send jack. It might be a bare wire for some people but I didn’t have one so I swapped it for a piece of wire I had sitting around. Disconnected and capped off the short white wire that went to the pot.

Works and sounds great. Thanks to anyone who reached out with paperwork and schematics.

 

[Kstarrguitar]

Yes this is very easy thanks for all the info guys I made mine look like this. FYI the white wire that was on the pot is tied back and you cannot see it. At first I just removed the white wire and soldered a jumper between the red and orange on the mix pot and yeah that works if your using the effects loop or a patch cable otherwise the amp will sound all whacky in and out like. So yes this picture is correct! You can do it like Gatroe’s pic if you don’t feel comfortable soldering!