Panasonic Hi-Fi Setup No Power Repaired
A customer sent to me his Panasonic Hi-Fi set up with no power symptom. As usual, I did not see any problems (visual inspection) in the power supply and mainboard.
In certain cases, you could see darkened fuse, dead lizard, corroded circuit line, burst capacitor, burnt resistors, dark patch on pcb board, loosen connectors and etc.
Next, I powered up the Hi-fi and check the DC output voltages and not even one output line have DC Volt (even with the connector removed). This means the issue is in the power supply section.
Since the power section was the suspect, I checked on the power FET and found it to be leaky.
All other surrounding or corresponding components seems to be good.
If you found one bad component in the primary side, it does not mean the secondary side components are okay. So I proceeded to check on the secondary side schottky diode and to my surprised, one of the diodes in the package was shorted (see photo below).
The part numbr was MBR20200FCT as seen in the below photo.
I installed both components and went through the 60 watt bulb test (by removing the main fuse) and the bulb did not light up fully indicated there was no more shorted components.
I took out the bulb and put back the main fuse and powered it up.
As expected, the Hi-fi came back to life and it was a relieved to me because I can charge the customer.
Conclusion- Visual inspection is very important if you want to do repair work. Spend some times to view on the board first before you turn on your meters to check on the critical points in any board. As a rule of thumb, always connect a light bulb to prevent the components that you have replaced in the power section to blow again.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous post about Haier 50 Inch LED TV With No Power Repaired
Andrew F. Ali
May 13, 2023 at 9:08 am
Very nicely explained. Excellent job.
May 13, 2023 at 9:09 am
Well done Suranga.
You are exactly right - you can't beat a good visual as the first step in the diagnostic process.
May 13, 2023 at 10:35 am
Very true! A naked eye view can help us detect many problems. Well done, dear!
May 13, 2023 at 1:06 pm
good job on the repair. I have a suggestion for you. you can check the youtube and build a current limiter and that way you can keep the fuse on and test it. it will save you time. that way you can test all your devices even they have shorts. have a blessed day
Albert van Bemmelen
May 13, 2023 at 3:38 pm
Fixing electronic defects is often expecting the unexpected to be prepared to face the problem before it escalates in causing more damage. And visual inspection is certainly one of them! Nice fix on this Panasonic set mr.Suranga!
Peter van Beveren
May 14, 2023 at 7:12 am
Good job...visual inspection is the starting point, although not the end point, of success.
May 15, 2023 at 7:35 pm
May 17, 2023 at 10:58 pm
Good Job! Suranga
May 18, 2023 at 1:11 am
That was a great job. Tho I wonder why manufacturers nolonger want to use linear(none smps) power supply in audio systems which hardly develop issues. Thanks all the same for the sharing.
May 23, 2023 at 6:56 pm
Good repair job. Thanks for sharing. The suggestion from another viewer is a good one for a current limiter with a light bulb and light switch and plug. Very easy to build. A lot of YouTube technicians use this setup.