The amp won't come out of standby unless the power cord is unplugged for about 20 seconds.
Once you do this it will come on and perform ok.
It can be turned on and off with no problem and will stay running indefinitely
When turned off for about 5 mins then won't come out of standby again.
I have just got a copy of the service manual looks like it may be the power good signal.
Anyone seen this before?
Check for electrolytic capacitors, especially in the power supply that are out of specs. You would be best off to use an ESR meter to find these. Once the bad ones are found, you can replace them.
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JANA _____
Once you do this it will come on and perform ok.
It can be turned on and off with no problem and will stay running indefinitely
When turned off for about 5 mins then won't come out of standby again.
I have just got a copy of the service manual looks like it may be the power good signal.
Anyone seen this before?
Such delayed effects are usually due to chemical effects within electrolytic capacitors, not necessarily the big ones. Check/monitor voltages over the ones around the protection circuitry, they may form a battery-like chemistry, so producing an offset, incorrectly interpreted as wonky power rails .
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
This could be a tough one. The generic replies about capacitors probably aren't going to help much.
I would look at the reset line for the micro - it could be drifting low and there have been a few problems involving the reset on these. The reset comes from the subtrans board, and loops through the Main (2) board up to the Function (2) board, which if I read the print correctly is the top "connect" board towards the rear of the unit, easily accessible for voltage measurements etc.
If the reset is dropping do not assume the fault is on the subtrans board, it would more likely be getting loaded down, possibly by a lead-free solder "whisker" issue or the like.
Mark Z.
ic
Found the problem the power good signal was low instead of high. Caused by low current in opto IC401 led, traced to C405 which is in series with the 240V AC. Difficult to diagnose as the area is at mains potential and there are no voltages marked on the diagram. The part of the circuit that regulates the standby 10 Volts through opto IC403 was working ok.
"Power good" was the reset from Q402, yes?
Mark Z.
Shoulda seen that. Thanks for the update.
Mark Z.
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