Sorensen DLM300-2 need blown part numbers.

[R-1125F]

I am working on an Sorensen  DLM300-2 power supply.  It shuts down when the voltage is turned up to 004.  It looks like the OVP is shutting down when adjusted to over 4 volts.  Some parts are damaged and I can’t read the part numbers. See attached photo. 

R385 is burned but looks like 4R?   Last digit is not readable. I would like to know the value of this part.

R322 looks overheated but appears to be a 22R1 or 20R1.  I would like to know the exact value.

Q48 is destroyed and code is not readable.   Q40 is a Onsemi P1F, PZT2222AT1.  I am guessing that that Q48 is the complementary PZT2907AT1.  Could someone verify this?

[fzabkar]

Can you identify Q101 and Q100? These appear to be the driver transistors. That should tell you whether the next stage is PNP or NPN.

[R-1125F]

Thank you.

Q101 is coded as 2F (2N2907A ?)
Q100 is coded as 1P (2N2222A ?)

[fzabkar]

Those two transistors are described as complementary to each other.

https://www.diodes.com/assets/Datasheets/ds30041.pdf
https://www.diodes.com/assets/Datasheets/MMBT2907A.pdf

Therefore, I think your guess for the damaged transistor is probably correct.

I would think that "4R?" is most likely to be 4R7, as this is a preferred value.

If we assume that this circuit is symmetrical, then R322 = R289 = 2001.

[R-1125F]

Should that be 4.7 Ohms or 4.7k Ohms?

[fzabkar]

R denotes a decimal point, so 4.7 ohms.

[coromonadalix]

r385  seems toasted

look a like symmetry ?

r288 = r321

not sure if r289 is =  r350 or r322 

WL3 ??   as the same value as R350   deductions seems right  = 1002 value ? oops loll 2001   be sure to measure it

[R-1125F]

I got everything back together and working but with one issue.  Without a load, the output transformer is buzzing.  Without a load, the buzzing get louder as the voltage is increased.  Under load it is quiet.  While is was buzzing I tried to press on the transformer winding and the core but there was no change.  As I said, there is no problem under load.   Could there still be a problem that is causing the transformer to buzz without a load?

[coromonadalix]

could be some "normal"  behavior   since some of theses psu can be phase controlled / pwm controlled  etc ... and the x-former run on light load

unless you remove it, and dip it in rosin with some vacuum air out, i would not touch it

i have other brand similar psu's,  and you do hear some supply noises   unless it is to loud ??

was it like this  before the problems ?

[R-1125F]

I bought this as not working so I don't know how it worked before.   I guess I should test it to see what the minimum load is needed to quiet down.  It didn't blow up when I put a heavy load on it, so that's a good sign.