Electronics > Repair

Hameg HM8143 broken, need a little help.

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shempe:
Hello,

I bought a "working" Power Supply a few weeks ago. It was not....ok.
I agreed with the seller on some return money because I think it is a good Power supply and worth a repair.
So after I bought it, my money box is mostly empty in the moment, and R&S ask for a hand and a limb in repair.
I decided I will try to repair it and if I can't fix -> R&S must do it.

First all looks ok and working, it start´s without an Error, I can set the Parameters local and remote.
But, when I enable the Output, Cannel 1 and 3 there is no regulation, Volts goes to some other Values and Amps are not there.
So it looks something is broken.
Because im lacking a Service Manual I can only guessing what is broken.

So I Inspected the Circuit and found something suspicious, one chip looks like it was loosing his smoke.

Can someone Identify this ic ?

Here the Smoky one



Here the other one from Channel 1.




A few pics from the Board´s because I know, someone like to see the whole thing.







Thanks a lot for your time and help.
Stefan

bktemp:
Looks like a TL431 shunt regulator.

mij59:
The TL431 is a good candidate, but its not the only problem, maybe the transistors close to the TL431.
Seems to me you got two identical boards, assuming that one is working you can compare it with the faulty one. 

shempe:
TL431B could be possible.

Yes there are 2 identical Boards but the regulation on the output is on both not working,
maybe because one channel is broken it affected also the other channel.

I will compare the components with the "working ?" channel.

Maybe it will give me a clue, what also wrong.

mij59:

--- Quote from: shempe on October 25, 2015, 03:08:37 pm ---
Yes there are 2 identical Boards but the regulation on the output is on both not working,
maybe because one channel is broken it affected also the other channel.


--- End quote ---

Both channels should be galvanic isolated, the only thing they have in common is the controller board for setting the voltage and current, maybe there is a problem with data transfer, e.g. by I2C or SPI.

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