Total Recall voltages and biasing Now with pictures!

[jimilee]

I can get a louder fuzz sound out of my BBDs. I have replaced the 4558s and the CD4047 with the same results. Every resistor and Cap checks out, reflowed everything. Where can I start?

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[jimilee]

I swear the pictures were there last night.


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[Scruffie]

How can you possibly have ~ -15v coming from the regulator and on IC1 power supply (pin 4) and 18V & 17V on all those other chips... you've either made a mistake measuring, there's a ground problem or something has gone horribly, horribly wrong.

I suppose out of that the compander looks most wrong but the voltages are nonsensical so I wouldn't trust that.

[jimilee]

How can you possibly have ~ -15v coming from the regulator and on IC1 power supply (pin 4) and 18V & 17V on all those other chips... you've either made a mistake measuring, there's a ground problem or something has gone horribly, horribly wrong.

I suppose out of that the compander looks most wrong but the voltages are nonsensical so I wouldn't trust that.

Ok, remeasured my voltages. I noticed something a little off. Could a trace be bad somewhere?


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[Scruffie]

I can't make heads or tails of it, 18V in to and out of the regulator?

For the time being I suggest taking the MN3005 out of the circuit as a precaution because if those voltages are actually right, they're 1V off terminal.

I can say that in relation to the (incorrect) supply voltage, IC5 pin 1-3 are obviously bad so there's something going on in that area, possibly a bad chip or electro (C22).

[jimilee]

I can't make heads or tails of it, 18V in to and out of the regulator?

For the time being I suggest taking the MN3005 out of the circuit as a precaution because if those voltages are actually right, they're 1V off terminal.

I can say that in relation to the (incorrect) supply voltage, IC5 pin 1-3 are obviously bad so there's something going on in that area, possibly a bad chip or electro (C22).

Thanks scruff. I'll have a look this evening. It's the 1 watt resistor that brings it down to 18 from 27.

[Scruffie]

I'm aware of how the power section on this works  I meant, your previous set of voltages had it correctly outputting -15V and I was pointing out that ain't right now so something may have killed the regulator or you're measurements are getting messed up somehow.

Please put up your previous voltages again, I need to see what's changed between the two.

[jimilee]

I'm aware of how the power section on this works  I meant, your previous set of voltages had it correctly outputting -15V and I was pointing out that ain't right now so something may have killed the regulator or you're measurements are getting messed up somehow.

Please put up your previous voltages again, I need to see what's changed between the two.

Sorry, I didn't mean to imply your didn't, it was just an observation.



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[jimilee]

Here is where we're at after I replaced C22. Poking better, half of  IC 5 is still whacky though. I replaced it with a couple of different ICs with the same result.



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[jimilee]

This one is trashed at this point. Solder PAFs keep coming off both sides. I'm pretty sure I'm just gonna order another one and give it a go. There are lots of screwy things happening on this one.


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[jimilee]

I think I figured it out. As I was building the second one, I discovered I swapped the polar and non polar 2u2 caps.


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