my onkio av reciever TX-SR501 was cutting on and off until it is completely off now .. it will not power on atall,, can somone tell me what could cause it
What could cause it ?
That's easy.
Anything and everything.
I suggest you take it to an electronics repair place.
That's easy.
Anything and everything.
I suggest you take it to an electronics repair place.
This model is entry level and according to reviews in 2003, it runs hot. That doesn't bode well for a long, trouble-free life. Locating the fault will likely be harder than you think because it may involve capacitor weaknesses that only show up with the right type of test equipment. User Abuser's advice to seek an electronics repair service is the best course of action as you seem unfamiliar with the design of today's consumer electronics.
You´ll have to troubleshoot it.
Here´s the service manual.
ONKYO TX-SR501/E SERVICE MANUAL Pdf Download | ManualsLib
You have the amplifier on your bench and can measure, as said above it can be 1000 different things, just for starters:
On page 18 I see 2 relays RL6901/6902 which seem to main rectifiers D6903/6904 and are controlled by transistor Q6901.
If they are not switched ON, amplifier will not have supply voltages, so start checking that.
Not sure what triggers Q6901.
The amplifier is very complex, schematics only show a small "window" each, I suggest you print them all , cut sheets where needed and tape them together so you can follow signal flow, otherwise it´s impossible.
I bet final schematic will be table size, not kidding.
I *suspect* power supply is self turning off, maybe it detects a problem (DC at the output? check that
Suggestion: please don´t label yor requests "help" or "a problem", *always* mention brand and model or your posts get lost.
"onkyo av receiver TX-SR501 cutting off" is WAY better than "help".
Good luck with your servicing.
Here´s the service manual.
ONKYO TX-SR501/E SERVICE MANUAL Pdf Download | ManualsLib
You have the amplifier on your bench and can measure, as said above it can be 1000 different things, just for starters:
On page 18 I see 2 relays RL6901/6902 which seem to main rectifiers D6903/6904 and are controlled by transistor Q6901.
If they are not switched ON, amplifier will not have supply voltages, so start checking that.
Not sure what triggers Q6901.
The amplifier is very complex, schematics only show a small "window" each, I suggest you print them all , cut sheets where needed and tape them together so you can follow signal flow, otherwise it´s impossible.
I bet final schematic will be table size, not kidding.
I *suspect* power supply is self turning off, maybe it detects a problem (DC at the output? check that
Suggestion: please don´t label yor requests "help" or "a problem", *always* mention brand and model or your posts get lost.
"onkyo av receiver TX-SR501 cutting off" is WAY better than "help".
Good luck with your servicing.
If you dont know much about electronics leave it to the experts or risk death.
Otherwise its down to faulty components.
Check power supply to start with, see if fuses blown and if not what voltage it is at.
If fuses aren't blown then you could do some powered up fault finding like tracing signals through and see where they disappear.
If fuses are blown then you must use power off component testing or you could cause further damage.
Could be just power supply caps gone or bridge rectifier gone.
all fuse is good.. 5 volts across power switch is there.... low voltage transfomer is good... high voltage transfomer is good.. help me to find where the base lead of Q6901 is connected
If you have a part number for Q6901 then google that to try and find the datasheet. That will give you the pin-out, then you can find the base.
You will need to understand the structure of the manual that JMFahey kindly found for you. Each numbered schematic is split into 2 pages. Therefore you will need to rejoin the page pairs which are above one another. The numbering sequence of the schematic numbers is not sequential.
You can print the page pairs and as suggested, tape them together. Or you can screenshot and join in graphics editor. See attached example.
Q6901 goes to SEC1H. This appears on NAETC-7833 which then appears on Schematic 2 which is the processor board. It appears the processor, pin 23 is preventing switch on by controlling Q6901. The processor is also receiving error inputs. PROTECT and VOLH, pins 1 and 2 seem to be the error inputs. Also POWER pin 26 from the processor seems to switch on the AC inlet relay.
You can see from the block diagram pages 10, 11 how the error signals are formed. Each power amplifier has a transistor to detect error current/voltage and the six transistor collectors are joined to form one error signal. You will need to determine how VOLH is derived. That's as far as I can go.
You can print the page pairs and as suggested, tape them together. Or you can screenshot and join in graphics editor. See attached example.
Q6901 goes to SEC1H. This appears on NAETC-7833 which then appears on Schematic 2 which is the processor board. It appears the processor, pin 23 is preventing switch on by controlling Q6901. The processor is also receiving error inputs. PROTECT and VOLH, pins 1 and 2 seem to be the error inputs. Also POWER pin 26 from the processor seems to switch on the AC inlet relay.
You can see from the block diagram pages 10, 11 how the error signals are formed. Each power amplifier has a transistor to detect error current/voltage and the six transistor collectors are joined to form one error signal. You will need to determine how VOLH is derived. That's as far as I can go.
For further troubleshooting you should put a light bulb in series with the mains supply. If you need to disable the protection in order to find the fault, it should stop things going bang. A variac would be better.
I can´t, the schematic is chopped into pieces, impossible to follow leads from page to page as shown, that´s why I suggested:
EDIT: just saw spladski kindly joined 2 sections for you.
You´ll need to do it for the whole amp.
Just one hint: *probably* microprocessor is doing its job, transistor, relays, rectifiers, transformer and caps are fine, and they are turned OFF because microprocessor discovered something funny, such as DC at one of the 6 power amp outputs, one of them blown, etc.
Personally I don´t even take such an amp for servicing, for the very good reason that time spent will quickly be more than what the product is worth, a lose-lose situation.
Here in Argentina, in Buenos Aires, a 14 million people city, probably there is somebody Factory Authorized or who "knows all things Onkyo", who is familiar with it and can recognize usual problems and solve in 1 hour, tops, so I´d send amp to him.
If in your Country you are the only option, and have to "learn Onkyo" while you repair it, as soon as you spent 4 or 5 hours into it you are losing money.
I would check that power amps are not shorted or passing DC which would trigger protection.
One way to do it is to feed them from another supply, *any* supply, even as low as +/- 20 or 25V, ALWAYS through a lamp bulb limiter, with a 25W to 40W bulb, no signal applied, no speakers connected.
You could spend 1 hour checking that, and if you find anything broken, repair it.
If you don´t find problem in 1 hour, close it and send it back to customer.
You are not FORCED to repair EVERYTHING, and if this amp happens to have a Logic problem, forget it.
I saw you formerly asked about PA power amps, those are more reasonable to repair, more straightforward, signal path is clear, supply and power amp too.
These "intelligent" flashy multiprocessed consumer products? Phew!!!!!
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I have a Technic av receiver that did that but not to the point of not losing the connection completely. The sound of the output relay chattered intermittently when that happened. The relays are quite beefy and pcb was a thin grade of phenolic. The click -on of the relay was loud so the mechanics involved are relatively vigorous.
I had thought there had been a dc issue behind this fault but pressing areas around the relay coil connections from the top of the pcb gently caused the relay to click in.
I took the pcb out and and sorted out the solder connections to the traces. The amplifier is still working after 5 years from the time of the repair. I think some vibration had a cumulative effect on the solder underneath. Twisting the tabs in the slots below would have helped secure this to the pcb.
I assume the power indicator light illuminates at switch on - is there any visual error indicator that does the same.
JMFahey makes a good point about time investment. However, the device may be good enough quality to justify it. Onkyo make good amplifiers supported with good documentation, not available for many expensive breeds. The quality of parts in the amp is also good with fast output transistors 2SC5198 and 2SA1941.
The service manual actually has all the info to shorten debug time. Page 42 is a block of the whole system with a breakdown of the protection elements. There are even test procedures! I think mjona suggesting solder joints is a good place to start since the failure mode was gradual. When everything turns class D it is not going to be easy.
The service manual actually has all the info to shorten debug time. Page 42 is a block of the whole system with a breakdown of the protection elements. There are even test procedures! I think mjona suggesting solder joints is a good place to start since the failure mode was gradual. When everything turns class D it is not going to be easy.
onkyo TX-SR501
well well i replace Q6901 although it was testing ok but the amp still not working... if i leave it pluged in for a while like about a hour to a hour and a half and then i press the power button it will cut off and on off and on at a fast rate.... ALL OUTPUT AND DRIVER TRANSISTORS TESTING GOOD.... across the power switch i'm getting 5 volts
well well i replace Q6901 although it was testing ok but the amp still not working... if i leave it pluged in for a while like about a hour to a hour and a half and then i press the power button it will cut off and on off and on at a fast rate.... ALL OUTPUT AND DRIVER TRANSISTORS TESTING GOOD.... across the power switch i'm getting 5 volts
Looking at page 19 Schematic Diagram I see dc monitoring of the left right and middle amplifier modules which connect to a switch which will ignore a.c because the capacitor in the network will not fully charge unless there is a d.c. voltage on the output. When this happens the sense transistor will turn on. I surmise further down the chain that would cause relay to cut out or not click in. That would be a matter of following the circuit board traces.
A simpler test would be to measure the base voltages on Q6070 and equivalents in other modules to identify any culprits.
A simpler test would be to measure the base voltages on Q6070 and equivalents in other modules to identify any culprits.
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