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JDSLabs BB-CMoy v2.02 Amp Issues

post #1 of 14
1/6/10 at 6:57pm
Thread Starter 
[Precursor]
Hey everyone - as my first DIY project I decided to go with the bassboost CMoy and everything went perfectly. However, while installing it into the chassis (altoids tin) I realized the wires for the external bass boost switch were too short. So I unsuccessfully tried to desolder cleanly, eventually I ended up just breaking the wires off accidentally and leaving the copper pads scorched to oblivion. So instead I soldered wires to the back of the PCB (for two of the wires, I had to solder them directly to the next inline hole, bypassing the boards circuits) I eventually got all the wires soldered back in, popped it into the enclosure and began to test the amp with my PC350's.
[/Precursor]

About 5 minutes in, I noticed the LED began to flicker, the SQ dropped dramatically, and I began to see smoke coming from the altoids tin. I rip out the battery, turn the lights on (it was 4am at this point) and identify the source of the smoke as the Texas Instruments IC (TLE2426). By now I'm pretty spooked because the thing nearly caught fire in my hand, but I go upstairs and check all the joints/solder points/connections and everything appears to be fine.

Here's the issue, it was working perfectly before I resoldered longer wires in, so I'm assuming they're the cause of the problem. So I've taken photos, can you guys see anything wrong with the soldering? (After taking the photos, I went ahead and reflowed all the cold solder joints/added more solder)

http://img63.imageshack.us/img63/6152/img0809c.jpg
http://img696.imageshack.us/img696/7772/img0810v.jpg
http://img43.imageshack.us/img43/1509/img0818un.jpg
http://img8.imageshack.us/img8/1231/img0821i.jpg

I'm pretty positive there's a short between V+ and Vgnd, but I can't find where. My multimeter doesn't have a continuity checker, instead I just measured the resistance and received the following:

V+ and Vgnd = 34.5 Ohms
V- and Vgnd = 0.553 KiloOhms
V+ and V- = 0.520 KiloOhms

Also took the voltage, the desired voltage is in parenthesis.

V+ and Vgnd = 1.372V (4.5V)
V- and Vgnd = -6.73V (-4.5V)
V+ and V- = 7.98V (9V)

Any help would be great, and I realize I'll need to replace the IC, but only after I find the short.
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post #2 of 14
1/6/10 at 7:30pm
I've got a bad feeling you've fed power into the IC the wrong way. A short circuit would have caused it not to operate at all and make the battery heat up quite badly.

I'd advise you to go over the switch wiring again and make sure it's correct, as that's probably where the problem is.

On another note: Did you try to desolder using a pump or wick? They cost next to nothing and are as handy as anything.

Ooops, just noticed. When you stuck it into the tin, did you cover up the wire joints on the bottom of the board? That could be a big culprit.
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post #3 of 14
1/6/10 at 7:40pm
Thread Starter 
I think the IC is oriented correctly for two reasons, one - it fits the pattern on the board, and two, the CMoy worked perfectly before I went ahead and resoldered. And regarding desoldering, I tried to desolder using copper braid, which ultimately failed because I couldn't get the solder out of the hole. I'll try to find a pump when I'm next at Radioshack (do they stock IC's?)

Cover them up? I used three layers of masking tape in the tin to prevent it from shorting out the board - if that's what you mean.
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post #4 of 14
1/6/10 at 7:55pm
Did you install another TLE2426 already?

If you did and checked it was put right way, then clean the PCB with ethanol or acetone and toothbrush. Short circuits that are invisible to the naked eye can be caused by flux residue.
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post #5 of 14
1/6/10 at 7:57pm
Thread Starter 
The flux visible in the photos was only temporary, I later cleaned it off before testing the resistance/volts (and testing the CMoy)

And no, I'd hate to burn another IC.
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post #6 of 14
1/6/10 at 8:35pm
Dunceiam: I would imagine Radioshack would sell the lower end version op-amps, but I doubt they'd sell the better ones.

I wasn't suggesting the chip was orientated the wrong way, just that the power was being supplied to the wrong pins via the short circuit.

The only thing I can think of now is desolder the wires again and check that no damage was done when you soldered/desoldered the wires. Then resolder the wires again, but make sure you solder them in a way that there is no chance of crating a short circuit.
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post #7 of 14
1/6/10 at 9:52pm
Thread Starter 
Quote:
Originally Posted by Pageygeeza View Post
Dunceiam: I would imagine Radioshack would sell the lower end version op-amps, but I doubt they'd sell the better ones.

I wasn't suggesting the chip was orientated the wrong way, just that the power was being supplied to the wrong pins via the short circuit.

The only thing I can think of now is desolder the wires again and check that no damage was done when you soldered/desoldered the wires. Then resolder the wires again, but make sure you solder them in a way that there is no chance of crating a short circuit.
I'll try it tomorrow and report back.

Simple question, how would you wire two 9V batteries in series? John (JDSLabs) sent the following, "In the mean time, you can remove U2 and use two 9V batteries wired in series. Connect the positive end to V+, the negative end to V-, and the center to Vgnd. Be very careful--batteries will behave similar to U2 if the circuit is not fixed."
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post #8 of 14
1/6/10 at 10:03pm
Dunceiam, obtain some desoldering braid and soldering flux. Try this:

1) Desolder all four wires and clean up the pads with the flux & braid. Once fixed, the amplifier will work fine this way (bass boost will be stuck "on").

2) Desolder the TLE2426 and clean those pads as well.

3) Remove the opamp

4) Repeat continuity measurements. If the short is cleared, solder in a new TLE2426. You might also need a new opamp.
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post #9 of 14
1/6/10 at 10:05pm
Thread Starter 
Quote:
Originally Posted by jseaber View Post
Dunceiam, obtain some desoldering braid and soldering flux. Try this:

1) Desolder all four wires and clean up the pads with the flux & braid. Once fixed, the amplifier will work fine this way (bass boost will be stuck "on").

2) Desolder the TLE2426 and clean those pads as well.

3) Remove the opamp

4) Repeat continuity measurements. If the short is cleared, solder in a new TLE2426. You might also need a new opamp.
Appreciate it, and will do.
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post #10 of 14
1/6/10 at 10:10pm
The switch behind the output socket looks like its started to melt you might need to change it as well,
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post #11 of 14
1/6/10 at 10:17pm
Thread Starter 
Quote:
Originally Posted by Fred_fred2004 View Post
The switch behind the output socket looks like its started to melt you might need to change it as well,
How much effect on SQ would a melted switch have?
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post #12 of 14
1/6/10 at 10:25pm
Quote:
Originally Posted by Dunceiam View Post
How much effect on SQ would a melted switch have?
Fred is correct. The short could possibly exist there. SQ is not the concern.
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post #13 of 14
1/6/10 at 10:28pm
Quote:
Originally Posted by Dunceiam View Post
I'll try it tomorrow and report back.

Simple question, how would you wire two 9V batteries in series? John (JDSLabs) sent the following, "In the mean time, you can remove U2 and use two 9V batteries wired in series. Connect the positive end to V+, the negative end to V-, and the center to Vgnd. Be very careful--batteries will behave similar to U2 if the circuit is not fixed."
Virtual Ground Circuits The bit about 2 batteries is what John is describing.

Do heed his warning though, as well as Tangent's about what happens if one battery should die before the other.
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post #14 of 14
1/7/10 at 12:10am
Don't sweat the SQ until the smoke clears
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