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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
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Old 5th July 2020, 12:48 PM   #971
thompsontechs is offline thompsontechs  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
Andy,


Check your wiring on Q12, I had the same issue and I had it miss wired the flying leads, easy to do. As for the higher rail, that's about right without a load.
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Old Yesterday, 06:37 AM   #972
andyr is offline andyr  Australia
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Quote:
Originally Posted by xrk971 View Post
Hi Andy,
Please measure the voltages at all major nodes in the circuit (each pin of each transistor) and redline a schematic with those values. That way, we can troubleshoot with you. Itís like going to a doctor when you are sick and donít know why. Dr needs diagnostics: vitals, bloodwork, xrays etc.

So far, we know the negative rail is sick.
Hi X. OK, measurements as follows:

* traffo input to the -ve rail: 19.49 AC
* 2SC5200 pin 1: -26.9v DC
pin 2: -25v DC ... and dropping
pin 3: -26.9 DC
* BD140 pins 1 & 3: -26.7
(can't safely get to pin2.)

Regards,
Andy

PS: Just now, I measured pin 2 of the 2SC5200 again - which is the -ve out voltage - and got -0.25v!!

Last edited by andyr; Yesterday at 06:44 AM.
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Old Yesterday, 06:46 AM   #973
andyr is offline andyr  Australia
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Quote:
Originally Posted by thompsontechs View Post
Andy,

Check your wiring on Q12, I had the same issue and I had it miss wired the flying leads, easy to do. As for the higher rail, that's about right without a load.
Thanks, JT. Just checked - the Q12 wiring is correct.

Andy
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Old Yesterday, 05:19 PM   #974
xrk971 is offline xrk971  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
It’s a slow effect. Look at your electrolytic capacitors C16, C18, something may be bad and takes time to show up. Looks like maybe a 30 second time constant?

What are other voltages when it goes bad? We need to know the voltage at the node of pin 3 of Q11.
Also accessible via the other parts connected to it. R16, C18, RV2.
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Last edited by xrk971; Yesterday at 05:26 PM.
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Old Yesterday, 06:16 PM   #975
nicoch58 is offline nicoch58  Europe
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will be a nice safety controll to avoid DC on speaker ....
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Old Yesterday, 09:28 PM   #976
xrk971 is offline xrk971  United States
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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
The problem Andy has is a malfunctioning PSU. We have DC protection for speakers here:

Ready-to-Run (RTR) SSR DC Speaker Protection and Delay GB
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