I'm gonna give up building soon

[evildead222]

IT WAS JOE DIRT! JOE DIRT! JOE DIRT!

[stevie1556]

I'm not thinking straight at the moment as I was up stupidly early for work today. But I've tested my AM Radios (both of them) with the continuity tester on my DMM. Checked the joints with it and all the wires and everything was fine. Apart from when I tested the power and ground.

If the power supply is off, then there is no continuity, but when the power is switched on, there is continuity between the two. Now, am I being silly in my sleepy state, or would I be correct in saying there is a short somewhere on the boards? Or is it just the DMM making a complete circuit?

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[muddyfox]

If the power supply is off, then there is no continuity, but when the power is switched on, there is continuity between the two.

I'm sorry Steve, I'm not following. "Between the two"... two what?
Is your pedal wired as true bypass?

[stevie1556]

I'm sorry Steve, I'm not following. "Between the two"... two what?
Is your pedal wired as true bypass?

Hey G,

I've just re-read what I wrote and it wasn't clear. I ment that when the power is switched off, there is no continuity between the positive and negative terminals. However, when the power is applied, with the pedal in either bypass or on, I get continuity between the + and - within the pedal. But, it's only if I put the positive probe of the DMM on ground, and the negative probe on any 9V connector.

Surely it should be the other way round. I'm pretty sure I've got the wiring right, unless I've messed up 7 wirings in a row.

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[muddyfox]

Errrr... so if I'm understanding you correctly, you are trying to test the continuity of the entire board?
It's been almost 20 years since I leant about these things last but here's what I (think I) remember.

Continuity testing is actually testing the resistance between your test points. If those two points are at a same electrical potential, there's no resistance between them and you consider them connected and your DMM beeps. When your battery isn't connected, you are measuring the resistance between 9V pad and a ground pad. Since there are components between those potentials, depending on what sort of components are there I'm guessing you could read anything between kOhms and MOhms on your DMM (and your DMM set for continuity wouldn't beep). Now, once you connect your 9V battery, everything changes. 9V battery has what, 1Ohm, 2Ohm internal resistance? On one side, your dmm sees a bunch of Ohms (your circuit) and on the other side it sees say 1Ohm and concludes that it's low enough and can be considered electrically connected and it beeps.
Again, it's been a while so I may be talking out of my arse but there's plenty of smart people who can set me straight if I misspoke.
Also, this in no way helps you troubleshoot your circuit.  As long as you have a dmm in hand, check continuity between your jacks and 3pdt, 3pdt and pcb and see if things change as they should when you press the switch (input gets connected to output on 3pdt etc).

[derevaun]

Yesterday I was testing a relay switching board that I had fabbed to use instead of the wicked switches CMOS switching scheme, because the latter board had a weird attenuated signal happening. And then, the relay switching scheme had the same tone-suck attenuated signal. So, the only advice I can give after nearly tossing out another board is, are you sure your cables are working OK?

In any case, having a didn't-work-on-first-try box is a really good idea. I wish I hadn't thrown out a board or two.

[lincolnic]

Actually, I'm pretty sure you shouldn't ever be reading continuity between power and ground. Sounds like you've got a short somewhere.

[aballen]

First off, that wiring looks gorgeous.  Don't quit, it would really be a shame to put those skills on a shelf.

I will say though, 7 pedals in such a short period is suspect.  That's a lot of work in a short period of time.  Consider the speed/quality/cost paradigm... You only get two.

You should rock before you box.  It's really the best way to know your circuit works. No 3pdt, jacks, or wiring etc to cloud the issue. 

To give you an idea, I just spent most of my weekend drilling and fitting four enclosures... Worked on the graphics made sure they fit too.   Next weekend I hope to have time to envirotex them... And maybe get them all permanently wired.  I probably took 2-3 months getting the boards stuffed and tested.

So what I'm saying is, take your time.  Pick one up from the pile of fail, take it out of the enclosure.  Get it working, box it back up, then move to the next.

You can get them all working... Just take your time... And maybe take a break before you dive back in.

[stevie1556]

Aballen - I know what you mean about taking your time with them. I have a fairly local place that drills them on CNC (it took me hours with marking out and using the drill press, and the holes still weren't accurately drilled). I'll then powder coat them and take them back down there to have the labels laser etched, so the box finishing doesn't take too long thankfully.

Lincolnic - That's what I thought but I think it's my tester is making the connection between the two.

Derevaun - I know a few of my cables are intermittent, but when I'm testing they seem to be ok. A box of fail is definitely a good idea, when I split with the ex last year I was in a rush to get out the house and threw away loads of non working circuits as I didn't have the space to pack them.

G - Cheers for sending the instructions on a audio probe!

Thanks to Muddyfox, I crudely constructed my first audio probe! One of these would have saved me so many hours on my previous box of fail! My AM Radios I found the problem, I didn't have a capacitor, so I stuck 2 together and they aren't working (the same technique has worked in another part of the circuit though). I now have sound coming out of them and the volume pot works, when the new caps come I'll swap them over and hopefully the gain pot will then be fully working. On the other one, I've somehow managed to swap the input and output jacks! It's basically a LofoMofo, and I must say, even with just the volume pot, it's great fun to play with!

Another pedal, after testing it again, it did seem to work, but with 'bop bop bop bop bop' coming through the speaker (really loudly). I found it was a bad IC, but when I was removing it I ripped up a pad. It's only a ground pad so I'll attempt to run a wire from it to ground. I'm just worried that all my ICs might be bad as they turned up in tin foil! FYI - desoldering a SMD chip is a PITA.

I'm on standby today, so if I'm not called out, I'll be designing a nice testing rig, with hopefully a few useful features. I've been very lucky to last this long without one though.

[muddyfox]

You may want to save yourself some time and wait for Jacob's testing rig that's (hopefully) about to make an appearance before long.
OTOH, any circuit design practice is good practice so you may want to do your own despite of it. 

[stevie1556]

You may want to save yourself some time and wait for Jacob's testing rig that's (hopefully) about to make an appearance before long.
OTOH, any circuit design practice is good practice so you may want to do your own despite of it. 

I've been waiting with baited breath since it was announced!  I've got the basics nearly laid out on paper, but if the testing rig if about to be released then I'll probably wait for that.

I want to say to everyone, a massive thank you for all the help and advice! Not only on this thread, but I used the search function recently to look some things up and the forum is truely a gigantic wealth of knowledge!

With my AM radios, they are now working! The new caps turned up, so I replaced the double cap solution that I did, and still no working gain pot. After scratching my head, I realised that I connected the gain pot after C1, not before. I scrapped the trace off the board, added a small wire, and now it works perfectly! Great little circuit, and great fun to play through! I've still got 8 boards left if anyone wants to try it out.

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