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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Yamaha RV-X450
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? |
#2
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Yamaha RV-X450
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. -- JANA _____ "jw51" wrote in message ... 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? |
#3
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Yamaha RV-X450
jw51 wrote in message
... 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? 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 http://home.graffiti.net/diverse:graffiti.net/ |
#4
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Yamaha RV-X450
"jw51" wrote in message ... 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? 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. |
#5
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Yamaha RV-X450
On Feb 20, 7:05*pm, "N Cook" wrote:
jw51 wrote in message ... 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? 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 onhttp://home..graffiti.net/diverse:graffiti.net/ 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. |
#6
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Yamaha RV-X450
"jw51" wrote in message ... On Feb 20, 7:05 pm, "N Cook" wrote: jw51 wrote in message ... 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? 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 onhttp://home.graffiti.net/diverse:graffiti.net/ 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. |
#7
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Yamaha RV-X450
Not from Q402 but from Q403 signal named PDET.
Mark D. Zacharias wrote: "jw51" wrote in message ... On Feb 20, 7:05 pm, "N Cook" wrote: jw51 wrote in message ... 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? 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 onhttp://home.graffiti.net/diverse:graffiti.net/ 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. |
#8
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Yamaha RV-X450
"jw51" wrote in message ... Not from Q402 but from Q403 signal named PDET. Mark D. Zacharias wrote: "jw51" wrote in message ... On Feb 20, 7:05 pm, "N Cook" wrote: jw51 wrote in message ... 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? 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 onhttp://home.graffiti.net/diverse:graffiti.net/ 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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