LM317 / LM337 Power Supply

Thread Starter

weyerma

Joined Oct 21, 2017
9
Hi all,

I have bought 2 of these power supplies. Now the problem is the negative voltage can be only trimmed down to -6.9v but i would need -5v.
Anyone of of you have an idea how i can mod the TL431 circuit at the LM337?
Its working in the positive circuit with the LM317.

Thanks
 

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AlbertHall

Joined Jun 4, 2014
8,762
R4 -10.8V / -3.7V
R3 -1.22V / 0V
I just noticed that the two resistors we are talking about are R3 and R41 (R4 is 220Ω across the LM337)

Set W2 for minimum voltage then measure the voltage between ground and:
The junction of R3 and W2
The junction of W2 and R41
The output voltage
 
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