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TV/VCR/Stereo Troubleshooting/Sony amp won't switch on, but does 'click'.

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QUESTION: Hi, my Sony STR-DH100 amp has recently stopped working. There's were some 'protect' issues a while back that I tried to fix by ensuring the wire to the speakers was in good condition, stripped correctly etc.

This seemed to fix that issue, but last week I went to turn it on and nothing appeared on the display. I heard a click sound which is the same as the one that I'd hear after the 'protect' message beforehand, but other than that, nothing.

I'm happy to take a look inside, but don't really know what I'm looking for. Any ideas?

ANSWER: First, remove all the speaker wires from the back of the set.  If you are still getting the click sound it means the problem is likely internal and most likely a failed power supply (such as bad rectifiers or transformer - something serious).

If it seems to be working with all speaker wires pulled then it might be you have a shorted speaker placing a dead load on one of the amps (a shorted voice coil inside one of the drivers can do this).  You can then test one speaker at a time.

Let me know how it goes.  Good Luck.  

Hope this helps.



---------- FOLLOW-UP ----------

QUESTION: Thanks for your prompt reply. I took a look inside and immediately saw that a fuse had blown. I replaced it today and was hopeful that this would fix things. Indeed, the display has reappeared, but within seconds of turning it on it comes up with the 'protect' warning  and shuts down. I've tried this both with the speakers plugged in and without any at all. Do  you reckon it's probably the power supply?

Answer
Yes, my guess would be the power supply. However, if you have in the past been driving the amp hard for long periods of time you could also have a melt down in one of the amplifier output stages.  This requires replacement of the output power transistor (or FET) which is no small task removing it from the heatsinks and soldering in new replacement devices (if you can find them).

In my opinion you might be better off, if you can, replace the entire amp.  Often you can find a working replacement on eBay or Craigslist that is more cost efficient than doing the repair.  If it turns out to be a shorted electrolytic cap in the power supply ripple filter section it would not be too bad to replace but still you have to get inside where you can rip out the old one(s) and solder in a replacement.  Not bad if you are an experienced tech but if you have never replaced a lytic before, now is the time to learn, I suppose.............

Best wishes.  Let me know how it goes.  

TV/VCR/Stereo Troubleshooting

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cleggsan

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Consumer Electronics of all kinds. Audio, esoteric audio systems and components, video, tv. Digital equipment for consumer use. Ham radio and automotive electronics. Note: I give advice on tv repair based on general consumer electronics engineering experience but I am not engaged in actual repair of sets. MAKE SURE YOU GIVE THE MAKE AND MODEL NUMBER AND AGE OF THE SET. BE SURE TO CHECK YOUR EMAIL FOR THE RETURN ANSWER DURING THE NEXT 24 HOURS AS I TRY TO REPLY TO ALL QUESTIONS WITHIN THE SAME DAY IF NOT THE SAME HOUR.

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Electrical Engineering; recording, broadcasting, design, international standards, tv and radio theory and practice.

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