DD-3 Mod Help

[Skubator]

So tonight I attempted the effects loop mod I found in this post over here: http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=47268e2a8809eda4e5fa2e476d2c7991&topic=42738.msg309116#msg309116

I've built a stompbox from a kit, and done a few mods on some of my other pedals successfully, but I'm still pretty new at this whole DIY thing and I'm having some trouble. I've got everything connected the way I think its supposed to be, but it's not working. For one thing, the pedal only works if I have something plugged into the direct out jack. I'm also getting a very loud buzzing sound as well; when I tested it with a guitar, I was able to hear the guitar under the buzzing, but the buzzing was much louder.

So, clearly I did something wrong! Based on what little I know about electronics, the buzzing makes me think that there's some sort of grounding issue involved. Also, something's got to be hooked up to the TRS jack wrong that it won't work without something plugged into it. I'd be more than happy to supply additional information as necessary, and thank you in advance for all of your help!

[duck_arse]

hello and welcome, skubator.

please be finding and posting the schematic [or links to] of the original pedal, and/or the schem with mods. and then post us some photos of your work, nice and clear shots of your wiring. but not too big, mind.

[Skubator]

Noted! I'll post some photos, and the schematic of the exact version of the DD-3 I'm working with tomorrow. It's 6AM where I'm at, so I'm just about to turn in for the night.

[Skubator]

So! Here are the innards of my DD-3 right now: https://i.imgur.com/xGfBvWw.jpg
I attached the original wires to the normal connectors of the TRS jack in the same configuration as the stock jack, and then jumpered from the normal side tip to the switched side ring connector. The yellow wire on the tip goes to node 22, and the purple wire on the ring (was originally blue, but I cut off too much replacing the jack and needed a longer wire haha) goes to node 2.

I was doing more research, and it sounds like I also need to cut the wire going to either node 12 or node 13, and connect my TRS jack there? Which connectors would I add that connection to? Also, the original post said to jumper from the wiper of the feedback pot to the tip of the TRS jack, so it sounds like that's something I did wrong. I'm not sure which node to jumper from in this case.

As for the schematic, it should be the one described in this service document: http://www.synfo.nl/servicemanuals/Boss/DD-3T_SERVICE_NOTES_3rd.pdf

Thanks again for all your help!

EDIT: bad image embedding
EDIT2: worse image embedding, so sorry.

[duck_arse]

I hate those jacks. the re-an one you added needs to be checked. I don't use them so I don't know the connections off the top of my head. the contacts short side-to-side, when you insert the plug one row of contacts disconnects, so if you've picked the wrong, performance is not as expected.

and if you wire the tip connection to a ring connection, inserting a mono plug will ground the signal, which may not be what you expected. save me wading thu that thread, what do you expect your mods to do?

[slacker]

I think like you said some of it is a ground problem, the original jack sockets are metal and only one of them has a ground wire attached the others are then grounded through the metal to metal connection with the case. You're using a plastic jack so if that black wire is the one going to the footswitch it isn't grounded. If the jack has a washer you can strip some wire and wrap it round the washer and then solder it to the ground lug on the jack that the black wire is attached to. The washer will press against the case and make a ground connection. Or if one of the other jacks has a ground wire you can add a wire from there to the ground lug on you jack.

Referring to the schematic to do the mod you just need to remove the wires between the direct out and the board,so the blue and yellow wires going to points 2 and 22. Then remove the wire joining C51 to the main board, points 9 on the schematic. Connect one point 9 to the tip of your jack and the other to the ring, with the wire to normalise it like you have now.

Like Duck said to connect a pedal in the loop you need a stereo to two mono splitter cable.

[Skubator]

So I would just remove the wires connecting nodes 2 and 22 entirely, so that nothing is connected at all? Then I would essentially take the wire connecting point 9 and cut it to add the TRS jack in between? Does it matter whether it's connected to the tip or the ring?

And as for your question Duck, the mod turns the direct out jack into a send-return loop. If you plug a stereo cable in, it lets you add other effects which get added to the repeats.

[slacker]

So I would just remove the wires connecting nodes 2 and 22 entirely.

Yes.
The way that part of the circuit works is point 22 has the dry signal on it which goes to the tip of the direct out. Point 2 goes to the ring of the direct out and controls Q2 via Q1, when nothing is plugged into the direct out the dry signal passes though Q2 to be mixed with the delayed sound to go to the Output. When you plug a mono jack into direct out it connects the ring to ground making Q1 open Q2 which cuts off the dry sound from the output, so you get delayed sound only from the output and dry signal from direct out. If you just completely disconnect point 2 and 22 then the pedal should work as normal as though nothing was plugged into the direct out.

Then I would essentially take the wire connecting point 9 and cut it to add the TRS jack in between? Does it matter whether it's connected to the tip or the ring?

Yes. Cut the wire and put the tip and ring in between. It doesn't matter which way round you connect tip and ring, the one that goes to the end of the wire that goes to the feedback pot will be the send and the other one will be the return.

[duck_arse]

hmm, well, I was going to put something, but I think slacker has a better idea as to what's going on here.

it would be nice to have a circuit diagram of the switch mod itself, for dopes like me. and, you still need to check the connections to the new socket are on the "moving" contacts (rather than the fixed contacts, which are NC when a plug is inserted).