Title: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 16, 2020, 12:55:49 AM
Post by: jimilee on January 16, 2020, 12:55:49 AM
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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Title: Re: Total Recall voltages and biasing
Post by: jimilee on January 16, 2020, 08:15:16 PM
Post by: jimilee on January 16, 2020, 08:15:16 PM
I swear the pictures were there last night.
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Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: Scruffie on January 16, 2020, 08:34:17 PM
Post by: Scruffie on January 16, 2020, 08:34:17 PM
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.
I suppose out of that the compander looks most wrong but the voltages are nonsensical so I wouldn't trust that.
Title: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 17, 2020, 12:35:36 AM
Post by: jimilee on January 17, 2020, 12:35:36 AM
Quote from: Scruffie on January 16, 2020, 08:34:17 PMOk, remeasured my voltages. I noticed something a little off. Could a trace be bad somewhere?
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.
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Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: Scruffie on January 17, 2020, 12:24:40 PM
Post by: Scruffie on January 17, 2020, 12:24:40 PM
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).
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).
Title: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 17, 2020, 01:02:25 PM
Post by: jimilee on January 17, 2020, 01:02:25 PM
Quote from: Scruffie on January 17, 2020, 12:24:40 PMThanks scruff. I'll have a look this evening. It's the 1 watt resistor that brings it down to 18 from 27.
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).
Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: Scruffie on January 17, 2020, 01:40:46 PM
Post by: Scruffie on January 17, 2020, 01:40:46 PM
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.
Please put up your previous voltages again, I need to see what's changed between the two.
Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 17, 2020, 01:42:39 PM
Post by: jimilee on January 17, 2020, 01:42:39 PM
Quote from: Scruffie on January 17, 2020, 01:40:46 PMSorry, I didn't mean to imply your didn't, it was just an observation.
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.
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Title: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 17, 2020, 11:45:34 PM
Post by: jimilee on January 17, 2020, 11:45:34 PM
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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Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 18, 2020, 04:10:04 PM
Post by: jimilee on January 18, 2020, 04:10:04 PM
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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Title: Re: Total Recall voltages and biasing Now with pictures!
Post by: jimilee on January 30, 2020, 02:30:08 AM
Post by: jimilee on January 30, 2020, 02:30:08 AM
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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