Effects DIY Troubleshooting

[Staccato]

Starting out with some DIY equipment/tools and two repair/finish projects, and have several questions before going forward.
(These were very low cost DIY projects-so far. Also found several good Muff effects sites with internal specs. online. And, have experience on radio shack soldering projects.)

The two projects (see photos):



• GGG Muff - BMP Kit not-yet-complete (incl. parts to make any of 7 Muffs) This one is new/nearly complete with two purple wires unsoldered and 'power on' light unsoldered. So far I have not connected it to power.



• Russian Big Muff-Black (Sovtek) This latest black version appears untampered with, and 'lights up' with a 9V (no power adapter option on the stock unit).
It needs troubleshooting for bad pots/switches/connections.

Questions for other DIY TB'rs:
1. How to test the pots and switches?
2. How to check other solder connections?
3. Already have the multimeter (below), is one of these necessary to troubleshoot?
4. Any other testing equip. recommended for testing?

On-hand-Multimeter:
Greenlee DM-40
Including:
• Audible continuity and diode test

On-hand soldering gear:
• Two soldering pencils;
• Soldering gun;
• Soldering stand/sponge.

[UncleFluffy]

Originally Posted by Stacatto

Questions for other DIY TB'rs:
1. How to test the pots and switches?
2. How to check other solder connections?
3. Already have the multimeter (below), is one of these necessary to troubleshoot?
4. Any other testing equip. recommended for testing?

1. In-circuit or out-of-circuit? It's much easier to test them out-of-circuit. Once they're in the circuit you need to take a look at what they're connected to to figure out what to expect. Most of the time the other components will give an effective extra resistance in series or parallel with the piece you're testing. If all you're wanting to check is "is this dead or alive", just look for a resistance change when turning the knob / flicking the switch.

2. 9 times out of 10 all you need is to jiggle the connection and if it's loose you should hear a crackle. If you're working from a "no output at all" situation, set your multimeter to measure current and put it in the supply line. Jiggling a loose connection may cause a temporary change in supply current.

3. If your meter is any good you don't need an additional continuity tester. An audible beep is nice, but not necessary.

4.

(a) Cheapo piezo earpiece - you can use this to trace the audio signal through a circuit. The impedance is high enough to not affect most circuits so you can just travel from input to output following the signal if it's at a high enough level.

(b) Oscilloscope, if it's in your budget. Wallet-friendly options are either an older 80s model from eBay (I'd avoid anything earlier than that due to weight and crankiness) or a software addon to a PC.

(c) LTSpice - build a software model of your circuit, note predicted DC voltage levels at each point, compare with what's actually there.

[moose23]

Good advice there but I'd just connect it all up and hope it works then if it doesn't then start working out what's wrong. You're soldering looks spot on to me so there's a good chance it will work if all the connections are right.

Here's a thread with a good list of things to check in addition to what Uncle Fluffy already mentioned:

http://www.diystompboxes.com/smfforu...?topic=29816.0

[UncleFluffy]

Originally Posted by moose23

Good advice there but I'd just connect it all up and hope it works then if it doesn't then start working out what's wrong. You're soldering looks spot on to me so there's a good chance it will work if all the connections are right.

Here's a thread with a good list of things to check in addition to what Uncle Fluffy already mentioned:

http://www.diystompboxes.com/smfforu...?topic=29816.0

For first power-on, put your meter in current mode in series with the supply before switching on. If you see a big current, switch off fast, because you've got a short somewhere.

If you're using a psu or a large battery, stick a 10 ohm 5W resistor in series to avoid popping the fuse in your meter. If just a PP3 then the extra resistor isn't necessary.

[Staccato]

Good advice, everyone! Thanks!

Yeah, I'm not new to soldering, but testing is a whole new ballgame for me. It's a slow process, but I'm starting to learn.

Looking for a separate DIY area on TB - one of these days...

[Jerry J]

Originally Posted by Stacatto

Good advice, everyone! Thanks!

Yeah, I'm not new to soldering, but testing is a whole new ballgame for me. It's a slow process, but I'm starting to learn.

Looking for a separate DIY area on TB - one of these days...

Hey John, good timing....look here.
Effects DIY forum on TB?

I think that if we show enough interest that a new forum would be feasible.

[rcubed]

My suggestions based on your photos would be to solder the components from the top side and for your leads, leave as little bare wire as you can showing. This will help eliminate mechanical connection issues that might arise. Also use the standoffs that were supplied, that way you know you're board won't move around inside and short something out.