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Digimess BP3002 PSU |
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peterb ![]() Senior Member ![]() ![]() Joined: 02 Feb 2017 Location: Cornwall Status: Offline Points: 330 |
![]() ![]() ![]() ![]() ![]() 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.![]() 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 |
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Peter
--------------------------------------- Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2 |
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gwebster ![]() Senior Member ![]() Joined: 04 Oct 2014 Location: Liss, UK Status: Offline Points: 175 |
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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
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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 ![]() Admin Group ![]() ![]() Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16280 |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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peterb ![]() Senior Member ![]() ![]() Joined: 02 Feb 2017 Location: Cornwall Status: Offline Points: 330 |
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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 !
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Peter
--------------------------------------- Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2 |
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peterb ![]() Senior Member ![]() ![]() Joined: 02 Feb 2017 Location: Cornwall Status: Offline Points: 330 |
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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.
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Peter
--------------------------------------- Dual 505-1, Cyrus CD T, DIY 80W MosFet amp and PreAmp, 2xKEF 103.2 |
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gwebster ![]() Senior Member ![]() Joined: 04 Oct 2014 Location: Liss, UK Status: Offline Points: 175 |
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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.
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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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