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Beolab 5000 diagnostics

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Frank Solem
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Norge
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Frank Solem posted on Tue, Mar 16 2021 6:51 PM

 

Hi

I have tried to search for a thread that describe diagnostics 101 for the Beolab 5000, but cannot find any.

I just purchased a tired one for way too much money, but are getting progress now. I have sanded the rust on most of the metal, except the bottom plate and some minor rust on some brackets. Given the trafo a new look(sorry, not original) and changed all capacitors.

I kept the original capacitor look of the mains cap and coupling caps. Just pulled the innards out and placed a brand new nichicon inside :) Gave them a spray, since they were so ugly.

When I finally powered it up slowly, it all seemed fine, but when I measured the centre voltage, I have 33V on the left coupling cap, the right have 55V.

According to user manual, this is a safety precaution to protect the outputs.

 

Any tips on where to start diagnostics? I am really not clever in that department. I can do the old Tandberg's, but that’s because I know them quite well. I have checked all output transistors, they measured fine. Power supply is fine. All resistors in the output measures fine. 

Should I just start pulling the transistors on the driver stages and test them? I don’t feel like changing all of them, unless they are gone. 

 

 

Any tips on where to start diagnostics? I am really not clever in that department. I can do the old Tandberg's, but thats because i know them quite well. I have checked all output transistors, they measured fine. Power supply is fine. All resistors in the output measures fine. 

Should I just start pulling the transistors on the driver stages and test them? I dont feel like changing all of them, unless they are gone. 

I will be glad and thankful for any thoughts.

 I cannot post pictures of the amp, for some reason i was told to try again in 30 minutes.

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Frank Solem
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Norge
13 Posts
OFFLINE
Bronze Member

All good, it was transistor 336, a BC154 that was faulty. Replaced with BC557BTA and now working fine.

 

What about the heat-problem on the resistor for the main light. Any well known solution for that?

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