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Philips "Black Tulip" 380/280 Pre-Amp Failure

A

abarrutia

New Member
Hello Forum!

We inherited a Philips Black Tulip set from our grandfather. Its been with us for a long time already and worked and sounded perfect until it started to fail. The problem is with the PreAmp 280 that a break circuit jumps after about 20-60 minutes of play. Upon cooling it down it works again and again the circuit Jumps.
Unfortunately its been to 2 different repair shops in the last years and none of them could solve the problem. For anyone that owns one of this and had this issue with the 280 pre, any advices would be greatly appreciated.
I'm based in Buenos Aires Argentina.

cheers,





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This shouldn't be that difficult a problem to diagnose by an experienced electronic shop. Basically what you do is run the system until it overheats, then use an IR camera to find the hot section and go from there. Do you know if either of the repair shops you brought it to tried that? Were they even able to reproduce the problem?
 
swechsler said:
This shouldn't be that difficult a problem to diagnose by an experienced electronic shop. Basically what you do is run the system until it overheats, then use an IR camera to find the hot section and go from there. Do you know if either of the repair shops you brought it to tried that? Were they even able to reproduce the problem?
Click to expand...
One of those cheap temp guns works great for me. That and a can of freeze spray. Find the hot part, hit it with freeze spray and see if it starts working again. Some parts like voltage dropping resistors and some voltage regulators can run pretty hot. That's normal in some instances.
You find heat sinks on some of those devices.
I found one that was running at its max rating. It got so hot it discolored the PCB. I added a heat sink to it and it runs nice and cool now.
With the IR camera, or cheap temp gun you should be able to find the transistor or transistors that are hot.
Also look for electrolytic caps that are close to any voltage dropping resistor or voltage regulator. Being so close to these parts can over heat these caps and cause them to drift in value or fail. You can sometimes see bulging on the top or sides of the cap and even burn markes.
 
Thank you both for your advices! I told them about the IR camera and they will do that test. Hopefully they solve the problem!
 
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