Linear PSU fix help

[sanchezxxx]

Hey All,

My Linear PSU used to power my Beresford / Dorado combo has stopped working.

When I turn on the PSU I get a little flicker on the bottom right of the voltage indicator display but nothing else. If I leave it on it will get warm but not show a voltage output or power up the Dorado.

Took it apart and noticed some discolouration around cable connecting to on/off switch and underside of the of the LTLinear chip where it connects to the circuit board.

Anyone have any ideas of what could be wrong / how to fix?

Much appreciated,

https://imageshack.com/i/pmcQgcrMj

https://imageshack.com/i/pn0N6I4ej

https://imageshack.com/i/pmNucpRPj

https://imageshack.com/i/pnk0aPNMj

[Firebottle]

Looks to me like the regulator was probably getting hot and has probably failed.

Replace it, LT1083, but beware there are fakes about from the far east. I bought a tube of 10 and none worked as they should have done.
Expect to pay £5-9 for a real one, if the price is a lot less they could be fake.

[willbewill]

Looks to me like the regulator was probably getting hot and has probably failed.

Replace it, LT1083, but beware there are fakes about from the far east. I bought a tube of 10 and none worked as they should have done.
Expect to pay £5-9 for a real one, if the price is a lot less they could be fake.

I had the very same problem with a similar PSU recently, regulator getting very hot! Mine was giving 22.2v before rectification so while the load was only 490mA the regulator was having to dissipate over 6w!! These PSUs don't perform as they promise and could even be quite dangerous.

[Mr. C]

I agree with Alan a lot of piss poor lt1083 kicking about if you would like a real one I do have one I can let you have.

In the end I just designed our own 10 amp regulators, heat dissapation is critical here especially if you having to drop voltages over 3.5Vdc

[Firebottle]

I had the very same problem with a similar PSU recently, regulator getting very hot! Mine was giving 22.2v before rectification so while the load was only 490mA the regulator was having to dissipate over 6w!! These PSUs don't perform as they promise and could even be quite dangerous.

Yes it's so much better to mount the regulator to the case, not a poxy little inadequate heatsink. The case would provide much better heat dissipation.

I have a Baldwin Hi-Fi psu that on first glance appeared well thought out, with the two pass transistors mounted on what appeared a solid aluminium bar attached to the case. On closer inspection the 'bar' was a thin finned heatsink with very little physical contact to the case.

I relocated the pass transistors to directly mounted on the base and it runs so much cooler.

[Mr. C]

Yes it's so much better to mount the regulator to the case, not a poxy little inadequate heatsink. The case would provide much better heat dissipation.

:)

[sanchezxxx]

That would be amazing. Will PM, thanks so much.

[Covenant]

Looks like you are on your way to being sorted. Are you going to replace it yourself?