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B1 preamp build thread
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Old 7th August 2018, 01:46 PM   #551
Zen Mod is offline Zen Mod  Serbia
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B1 preamp build thread
right now I can't understand what's wrong - PSU or whatever you connect to it

anyway - if PSU isn't having intended voltages at outputs, just replace LM regs where voltage isn't ok

simple as that
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Old 7th August 2018, 01:53 PM   #552
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the issue was that by accident i attached the power supply to my b1 with reversed polarity (that was 2 month ago). you helped me troubleshoot the b1 and it seemed not to have taken any damage.

then you gave me advice on how to check if the psu survived the reverse polarity. to do so you advised me to attach 1r resistors in line with the rails and measure voltage across them. this is what i just did and the voltage is exactly the same as without resistors. now i was wondering
1) what the purpose of the measurement with the resistors in line is?
2) if that tells me that the psu is fine?

the voltage between +/- is 30v. 15v if i measure across "+" and ground or " - " and ground. that's the way its supposed to be i guess.

sorry for the confusion
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Old 7th August 2018, 02:23 PM   #553
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in line resistors where there to measure voltage sag across them , and reflect is there any malfunction

it was supposed that you do that and write back your findings , so we can proceed further if needed , or declare it OK

this way , asking zillion years later , you're just adding confusion to already confused ZM

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Old 7th August 2018, 02:26 PM   #554
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i understand that my reply comes a little late - sorry for the confusion!

seems that there is no voltage sag across the resistors, does that mean the PSU can be declared ok?
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Old 7th August 2018, 02:43 PM   #555
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B1 preamp build thread
If you measure +/-15V on the output of that PSU it's probably fine. However, what isn't fine is that you seem to have a dual-rail PSU supplying a single-rail amplifier. Can you draw how the two boards are connected together? From an earlier picture it looks like you have previously run the B1 on two 9V-batteries in series - did it hum then?
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Old 8th August 2018, 01:41 PM   #556
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Quote:
Originally Posted by Nisbeth View Post
If you measure +/-15V on the output of that PSU it's probably fine. However, what isn't fine is that you seem to have a dual-rail PSU supplying a single-rail amplifier. Can you draw how the two boards are connected together? From an earlier picture it looks like you have previously run the B1 on two 9V-batteries in series - did it hum then?
i'm afraid you're quite right. i did use the dual power supply for the (single rail) b1. i have to admit that i really only used it for maybe 5 seconds - with reverse polarity as mentioned before. after that i only used the two 9V batteries. and yes, there was some hum - how did you know?

unfortunately i don't remember how i connected the together. i believe +15v to '-' on the B1 and -15v to '+' on the B1. Wrong obviously.

Would it be possible to use a dual supply for a single rail amp at all?
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Old 8th August 2018, 02:03 PM   #557
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quite possible
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