Boneyard Issues--Resolved!

[jkokura]

Oooh...

If your battery is draining fast, that might mean you power is leaking to ground. Does that battery get hot while that's happening?

Jacob

[Myramyd]

Doesn't seem to be getting hot yet. But, it went from 9.33 to 8.09 pretty quick.

I can't see anything off hand where the power lines are going to ground.

But, that would make sense. It does sound a little like when a fuzz gets low voltage fed to it.

J

[jkokura]

If your battery died that quickly, I'd be using my DMM to do a continuity check between ground and power. You DEFINITELY have an issue with your power, and you need to sort that out.

jacob

[Myramyd]

Okay,

My current DMM doesn't have a continuity check on it (stupid Rat Shack!). So I'm going to get a new one and trace the power & grounds with that. I will report back after that happens. Hopefully tomorrow.

J

[madbean]

I'll put some detailed thoughts in ASAP, but one thing: DC on pins 1-2 and 5-7 should be 0v as you've shown. The power supply is bi-polar, and the reference voltages sits exactly in the middle, which is 0v. It's the same with the Plexitone, except in that case it's +-12v instead of 9v.

I'll try and read over everything else tonight and post more.

[Myramyd]

Thanks so much Brian, I really appreciate it!

J

[madbean]

Correction, I forgot that the order of the op-amps in the PCB design is different. Here are the approximate voltages you should be reading:
This is off an 8.89v supply using a TC1044SCPA charge pump and LM347n

1-> -2v
2-> 0
3-> 0
4-> 8.86v
5-> 0
6-> 0
7-> 0
8-> 0
9-> 0
10-> 0
11-> -8.39v
12-> 0
13-> 0
14-> 0

Interestingly, pin8 sometimes seems to read differently on mine. At first I used an auto-sensing DMM to do the voltages and it did not seem to work well. On my old cheapie I got more reliable results. The output should be 0v, and that's why a de-coupling cap was not used in the original design, I'm guessing.

More later.

[Myramyd]

So, I'm back to looking at this again...

I can't find any new issues. I can say that there is no voltage reading at any of the grounds.

I'm about to just order a second board and start over with all new parts. I have a feeling there is a bad part or two somewhere but I don't know how to figure out which ones. I suppose I could just try a new LM347N first.

Any other ideas I can try?

J

[Myramyd]

Here's an update...

I got a new LM347N and replaced the MAXX1044 with a TC1044 for good measure.

The voltages now match Madbeans and it overall has a decent tone but there are still two issues.

1- Not enough gain: The "high-gain" setting sounds about like what I think the low-gain should sound like. The low gain is about like a TS on half gain. This is with both gain knobs on max.

2- Tone knob: doesn't really function. It's more like a high cut. In the demos I've seen people have it about half way and it's pretty trebly. With mine, all the way up still sounds a little dull.

Any thoughts or should I buy a new board and start over? This thing has taken the damn life out of me!

J