Author Topic: Strange noise

January 18, 2022, 10:11:58 pm
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Pierre

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Hi,
I have 2 issues :
- i don’t have -16V when i test V-
- when i turn on , i hear a little electric buzz, it come regulary, and stop, like a clock. This sound come from the switcher. For the moment i can’t test the switcher, because i don’t have 12V Electric device 

Big big thanks for your help !!!

January 19, 2022, 09:45:10 am
Reply #1

JPK

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You do need to test the switcher alone in order to find out where is the issue.
You can use the power adapter as a 12V source.
JPK

January 22, 2022, 11:15:21 pm
Reply #2

Pierre

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Hello

I just test the switcher 
I don’t have -19V , i have -33V
I don’t have +19v, i have 17 to 26 V
I don’t have 55V, i have 86V

I test the whole 501 too :

I have 11,86v (not exactly 12v)
I have 38 to 51 V (for 48v test)
I have -16V
But i don’t have +16v (1 or 2 V)

Maybe i damaged some component with too much heat ??

Always a little buzz

CAN i do something?
Thanks!!

January 23, 2022, 09:06:24 am
Reply #3

JPK

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So the switcher works, good point!
Check that the case of U1 (LM317T) is not touching any pad or track on the PCB.
Look for a solder bridge on the main PCB.
You can check with the ohmmeter if you have a short circuit between 0V and +16V (finger #12 down).
JPK

January 24, 2022, 11:08:00 pm
Reply #4

Pierre

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Hi, i had to do a better solder for the LM317T
And after, i did all the test again : and it work great !!!

But, when i screw everything in the box , i had to press a little because it's a little narrow
I turn on : nothing:'(:'(

I take everything off the box
And test again
The main pcb work ok
But the switcher don't work now
All the switcher test failed
And no little buzz too
No red ligh
i checked every solder, because i could destroy a solder with the pressure i made to put everything in the box
But a don't see any issue

It's strange
Any advices?
Thanks




January 25, 2022, 04:58:18 pm
Reply #5

JPK

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Try to see what the pressing may have moved?
Probably a solder joint somewhere.
JPK

January 25, 2022, 08:25:02 pm
Reply #6

Pierre

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Hi
I open the switcher and check all the solder joint, nothing move, i check especialy the inductances radiales and the electrolytic condenseur, because it's the higher component, so the pressure could crush'em, but nothing moves, solders look ok
Honnestly i don't now where is the problem. 
Everything works great before i put it in the box
Should i test each component? I don't really know how to do
Thanks!

January 26, 2022, 11:04:00 am
Reply #7

JPK

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Difficult to say from a distance.
Maybe you can send us the switcher for a diagnosis?
JPK

January 28, 2022, 06:52:03 am
Reply #8

Pierre

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Ok, i'll send you an email to know how send it to you