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Old 21st May 2010, 03:27 PM   #1
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Default Sony receiver won't turn on - need help

I received a "broken" Sony STR-DH500 from a friend and I'm on a mission to fix it.
When I plug the receiver into 110V and tap the power button, all I hear is a single relay click and then...nothing. No PROTECT, no error message, no additional clicking.

Can someone start me on a path on how to troubleshoot the thing?
I've opened it up, cleaned it out, disconnected everything externally (speaker wires,...) and checked for visual damages on the circuitboard and components.

I just need some help getting started.
A link to a service manual would be great too, if it even exists
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Old 21st May 2010, 03:46 PM   #2
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check regulators for voltage ,mains secondary fuses , transformer and so on ...there is a posibility that the click comes out of stand by relay and circuits but if fuses or trafo is gone makes sense that you hear or see nothing

this is no project for an amature ....you need skills to trouble shoot amplifier like that if you need schematic please email me

regards sakis
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 21st May 2010, 04:15 PM   #3
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thank! check your email!
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Old 21st May 2010, 04:52 PM   #4
macboy is offline macboy  Canada
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Sony does publish good service manuals. Like all service manuals, they don't include instructions on how to troubleshoot, but include schematics. Helpfully, the schematics are usually marked up with expected voltages and waveforms at many important nodes. If you can't find it elsewhere, try Agoraquest - Great Sony Forum, News, Reviews with 90,000 members

Sony amp power supplies are based on a separate standby and main power transformer. It seems the standby power works since you hear that click upon pressing the power button. You should find an AC power board inside, this will have a small transformer (for the 12 VDC standby power supply), a relay, and various supporting components. This relay should allow AC into the big main power transformer. Try measuring for 120 VAC at the primary of the main power transformer. This is a good time to mention that there are deadly AC and DC voltages inside a receiver so use caution and do this at your own risk. There is probably a fuse for the main power trafo primary, as well as some or all of the secondaries. When replacing fuses, never use anything but the same type and rating (current and fast/slow blow). If the thing is blowing fuses, you can't fix it by putting in a higher rated or slow-blow fuse. You will only cause more damage. The VFD display is powered from the main power trafo so no display tells me there is maybe a blown primary fuse. (The secondary for the VFD usually isn't fused).

Can you turn it on and off with the remote? If so, the system microcontroller is basically functioning, which is good.
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Old 21st May 2010, 05:20 PM   #5
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you guys are brilliant. I will give this a try tonight/tomorrow and report back!
I am engineer and am familiar with circuits and dangers and I appreciate the cautions.
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Old 23rd May 2010, 01:54 AM   #6
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I took the receiver apart and tried to measure voltages at various points throughout the system.
The stand-by transformer seems to work and send 110V to the main transformer. I checked the input leads of the main and it does get 110V, but it's outputs are all zero.
I disconnected the transformer and did a resistance check on the primary and secondary windings. All secondary windings came out as a short, as expected, but the primary winding is giving me an open-circuit (infinite resistance).
I thought it's more likely to burn up secondary windings than primary windings, but apparently something went poof with the primary windings or some solder joint to the windings.

Where could I get replacement Sony transformers (Bando brand) for my unit? What's the expected cost of one?
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Old 23rd May 2010, 03:52 AM   #7
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It does appear that the primary winding is open. However, many transformers have an internal fuse or temperature sensitive device that, once opened, stays that way. You might be able to take apart the transformer and find it. So the transformer might be good, just that the thermal device failed. Worth a look, I think.

The device is usually around the size of a small fuse and wrapped in insulating tape. Yours could be different.
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Old 23rd May 2010, 03:32 PM   #8
tomw75 is offline tomw75  United States
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I have several bando xformers your's have a type number on it?
tomw75
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Old 23rd May 2010, 06:37 PM   #9
macboy is offline macboy  Canada
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If you find a burned thermal fuse in the transformer as suggested by bob91343, make sure to replace it with a similar device. Don't just short it out. It is a protection device; you don't want to burn down your house.
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Old 23rd May 2010, 06:40 PM   #10
macboy is offline macboy  Canada
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You can try to find a replacement transformer at sony parts direct: https://servicesales.sel.sony.com/ec.../web/index.jsp or by phoning them. They will sell service parts to individuals, and they will help you look up the part over the phone.
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