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Digimess BP3002 PSU
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peterb View Drop Down
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    Posted: 09 Mar 2023 at 3:14pm
Dual 30V 3A Linear PSU.
Possibly wishful thinking but does anybody know where I might find a circuit schematic for my PSU, the +ve channel voltage is unstable below about 20V, the manufacturer has gone to the wall.Dead
I have opened up the case and it seems to comprise of several secondary transformer tappings feeding LM regulators, Op Amps and 2 power transistors, please see photo. The -ve channel seems to use exactly the same components as the +ve.
Thanks.




Edited by peterb - 09 Mar 2023 at 3:15pm
Peter
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Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2
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gwebster View Drop Down
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Having a search on the internet came up with this, which may be worth following up:

Also, if the two channels are identical, a direct comparison of voltages around the circuit could pinpoint the problem. If is going unstable below a voltage, I would suggest a decoupling capacitor in the voltage reference feedback loop has gone (channel oscillating).

Geoff
Inspire Apollo tt, O/L modded RB250, Ortofon 2M Black, Slee Different Approach inspired Phono, Putzeys Pre, Cusat, Raspberry Pi/Volumio, Bitzie, Self Load Invariant Power, Acoustic Energy AE509s
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Graham Slee View Drop Down
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Points: 15025 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2023 at 10:28am
Try https://elektrotanya.com/
My blog is sponsored by Cadman Enterprises Limited
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peterb View Drop Down
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Points: 279 		Post Options Post Options   Thanks (0) Thanks(0)   Quote peterb Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2023 at 10:44am
Thanks Geoff and Graham.
Geoff: Yes my thoughts exactly about comparing voltages and a capacitor fault. 
I have bought the circuit diagrams option (£5) to check if my model is listed, waiting for its arrival.
Graham: I am afraid searching that site came back with nothing. 

I have to say I am puzzled that the circuit uses fixed voltage LMs and not the variable voltage ones. If I can get a schematic maybe it will become clearer !
Peter
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Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2
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peterb View Drop Down
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Points: 279 		Post Options Post Options   Thanks (1) Thanks(1)   Quote peterb Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2023 at 10:10pm
Geoff your link turned up trumps, not just a likely schematic but an email contact that used to be a director of the old Company!
I have followed his suggestions and I still can't believe it, cleaning the control pot fixed it !!
Now I just have to take it apart again to clean the other pots, then it is good to go. Smile
Peter
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Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2
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gwebster View Drop Down
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Points: 165 		Post Options Post Options   Thanks (0) Thanks(0)   Quote gwebster Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2023 at 8:12am
Pleased to hear its fixed. Funnily enough, as I read your previous post, it had occurred to me that it could just be a dirty pot. 
Inspire Apollo tt, O/L modded RB250, Ortofon 2M Black, Slee Different Approach inspired Phono, Putzeys Pre, Cusat, Raspberry Pi/Volumio, Bitzie, Self Load Invariant Power, Acoustic Energy AE509s
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