Sony Home Cinema Amp STR KSL5 problem

I have a SONY a home Cinema system (STR KSL5) which after about 2 mins shuts down with the word PROTECT in the display screen. I have checked all the speaker outputs and they are fine, no shorts. I have removed all the speakers and the same problem occurs. The fan works so doesn't seem to be an overheating problem. This PROTECT fault occurs even when the volume is turned right down therefore not driving the amp. Anyone have any ideas what might cause this fault? and how to rectify it?

Thanks

Davy H

Reply to
Davy H
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Sounds like an overheating (i.e., thermal intermittent) prob to me if it's shutting down after 2 mins. That the fan is functioning doesn't preclude a thermal defect in one or more components.

Get a can of component chiller (Freeze-It, et al) and spray each component in the amp chain, beginning with the higher-current devices at the final output stages. Allow the chilled part to warm up before proceeding to the next one.

Alternatively, allow the unit to _fully_ cool, then manually heat components with a soldering iron or finely tipped heat gun -- some techs use the reverse (blow) mode of their desoldering guns -- within that 2 minute window. Be very careful using this approach, as you can destroy a component if you apply heat to it for too long or otherwise go beyond its designed safety margins.

Reply to
Ray L. Volts

This is what I get for usenetting when I'm barely awake. Obviously, if the protection circuit has shut down the final stages, they won't warm up again until the thermal fault is corrected, as power is likely not being applied to them. You may have to give blanket coverage to several components at once to bring the unit out of shutdown. Once you've determined the general area at fault, you can hone in on the specific part(s) that is/are causing the problem.

Reply to
Ray L. Volts

Bad joints on the output IC pins are very common on Sony A/V amps, and cause the unit to go into protect like this

Arfa

Reply to
Arfa Daily

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Could be any of the 5 output amps, the sensing circuits or the CPU IC. = You'll need a schematic to troubleshoot it. All 5 amps have a transistor = Q401-Q405 2SA1162 (Protect) near them which monitor current flow to that = output amp IC. These 5 all connect together to Q406 near IC321 on the = main board.

Q406 should have +5V on the collector. That goes to pin 2 of IC321, out = pin 3 of IC 321, then out connector D to Digital board, thru R112 to pin =

53 of IC101 (CPU IC) on the digital board.=20

If you have +5V on pin 53, the CPU is bad. Part # 6-800-673-01 IC101 = MB90553ABPF-G-209-BND. You won't, so you have to find out where the = problem is.

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Reply to
Michael Kinnaird

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