Help please!
I recently purchased a lovely Sony TA-F770ES integrated amp with a known intermittent fault.
The seller described the fault like this:
"A noise/crackling/slight loss of sound on either the left or right channel, never both at the same time. Switching from 'Source' to 'Direct' and back to 'source' cures the problem".
The seller had enquired with a professional repairer and was told that cleaning the switch and checking for any dry solders would cure the problem. He was quoted £200 for the work and so decided to sell it as faulty instead.
And that's where I come in.....When the amp arrived with me it did indeed work but with the fault as described above.
I started the refurbishment of the amp by giving it a good clean with a vacuum cleaner inside and out (it was filthy!!) and then readjusted the bias and offset following the instructions in the service manual which went perfectly without any problems.
I then set about dismantling the unit to clean any switches and repair any dry solder joints. The further I dismantled the player the more dirty switches and dry joints I found and in the end I'd pretty well completely dismantled the entire amp. Oh well I thought, at least when it's back together it'll be all the better for it.
Sadly that's not been the case and now I don't have any output from the amp. Nothing, nada, zilch. 🙁
When the unit is powered on the protection circuit light goes off (well changes red to green) and you can hear a click from the speaker relay(s). But there's no audio output at all via either the headphone jack or speakers terminals.
I've disassembled and reassembled the whole thing several times now trying to find my mistake and I cannot see anything wrong.
I'm at a loss as to how to go troubleshooting and need some advice please! I have limited understanding of electronics but I do have a copy of the service manual, a good digital multimeter an oscilloscope and a steady hand.
The service manual can be downloaded here: Sony TA-F770ES - Manual - Stereo Amplifier - HiFi Engine
Any help will be most gratefully received!
I recently purchased a lovely Sony TA-F770ES integrated amp with a known intermittent fault.
The seller described the fault like this:
"A noise/crackling/slight loss of sound on either the left or right channel, never both at the same time. Switching from 'Source' to 'Direct' and back to 'source' cures the problem".
The seller had enquired with a professional repairer and was told that cleaning the switch and checking for any dry solders would cure the problem. He was quoted £200 for the work and so decided to sell it as faulty instead.
And that's where I come in.....When the amp arrived with me it did indeed work but with the fault as described above.
I started the refurbishment of the amp by giving it a good clean with a vacuum cleaner inside and out (it was filthy!!) and then readjusted the bias and offset following the instructions in the service manual which went perfectly without any problems.
I then set about dismantling the unit to clean any switches and repair any dry solder joints. The further I dismantled the player the more dirty switches and dry joints I found and in the end I'd pretty well completely dismantled the entire amp. Oh well I thought, at least when it's back together it'll be all the better for it.
Sadly that's not been the case and now I don't have any output from the amp. Nothing, nada, zilch. 🙁
When the unit is powered on the protection circuit light goes off (well changes red to green) and you can hear a click from the speaker relay(s). But there's no audio output at all via either the headphone jack or speakers terminals.
I've disassembled and reassembled the whole thing several times now trying to find my mistake and I cannot see anything wrong.
I'm at a loss as to how to go troubleshooting and need some advice please! I have limited understanding of electronics but I do have a copy of the service manual, a good digital multimeter an oscilloscope and a steady hand.
The service manual can be downloaded here: Sony TA-F770ES - Manual - Stereo Amplifier - HiFi Engine
Any help will be most gratefully received!
That must be something really basic.
First make sure the unit is set up correctly. Correct input, Speakers A, Mode Stereo, Subsonic Off, Direct Input on Direct for the time being. Make sure Adaptor bridges are installed if required. Try headphones. Still nothing?
Try feeding in a test signal like a sine, select correct input, clip the scope on circuit ground and poke around (a) at the volume pot and (b) at the input selector switch. If memory serves these units should have a mechanical source selector, so its setting should be kept after power off.
First make sure the unit is set up correctly. Correct input, Speakers A, Mode Stereo, Subsonic Off, Direct Input on Direct for the time being. Make sure Adaptor bridges are installed if required. Try headphones. Still nothing?
Try feeding in a test signal like a sine, select correct input, clip the scope on circuit ground and poke around (a) at the volume pot and (b) at the input selector switch. If memory serves these units should have a mechanical source selector, so its setting should be kept after power off.
The external graphic must be used or the links installed. If the links are installed, remove them and insert a signal directly to the power amplifiers. That will tell you whether the fault is the amplifiers or the pre amp side.
As a retired Sony Agent, a repair on these old amplifiers would have been charged out at £50 plus VAT. If new capacitors were required, that would be added if the customer wanted them. If we were to charge £200 we would not have been a Sony Authorised Agent for long!
As a retired Sony Agent, a repair on these old amplifiers would have been charged out at £50 plus VAT. If new capacitors were required, that would be added if the customer wanted them. If we were to charge £200 we would not have been a Sony Authorised Agent for long!
Thanks for the replies folks.
Having a poke around with the scope while a test tone is connected at the inputs seems like a very sensible idea.
My gut feeling is that there's nothing majorly wrong. I've probably just done something silly when rebuilding it, trouble is I've no idea what that might be.
If either of you chaps feels charitable enough to 'spoon feed' me with some specific instructions on where exactly on the circuit to test for the test tone that'd be superb.
I'll see what I can do....
Having a poke around with the scope while a test tone is connected at the inputs seems like a very sensible idea.
My gut feeling is that there's nothing majorly wrong. I've probably just done something silly when rebuilding it, trouble is I've no idea what that might be.
If either of you chaps feels charitable enough to 'spoon feed' me with some specific instructions on where exactly on the circuit to test for the test tone that'd be superb.
I'll see what I can do....
> where exactly on the circuit to test for the test tone
There's no water at the upstairs faucet.
A basic approach would be to drill the water pipes to see if water came out. From the upstairs faucet all the way out to the street. (FWIW-- I have diagnosed a car exhaust system this way. But that's not instructive here.)
OK, we don't troubleshoot water that way. But in electricity it is the only way (we can't see electricity but we can poke a meter without leaving puddles).
You know how an amp works, big-block. Phono to phono jack, phono preamp. Switching to select CD instead. Volume control. Line amp. Tone stage. Power amp. Speaker relay. On a fancy amp, there will be tape loops and EQ loops where you can tap for signal. The manual may have a Block Diagram you can copy and mark-up with observations. Same as you might sketch your house water plumbing and mark where you hit dry holes and where you made puddles.
There's no water at the upstairs faucet.
A basic approach would be to drill the water pipes to see if water came out. From the upstairs faucet all the way out to the street. (FWIW-- I have diagnosed a car exhaust system this way. But that's not instructive here.)
OK, we don't troubleshoot water that way. But in electricity it is the only way (we can't see electricity but we can poke a meter without leaving puddles).
You know how an amp works, big-block. Phono to phono jack, phono preamp. Switching to select CD instead. Volume control. Line amp. Tone stage. Power amp. Speaker relay. On a fancy amp, there will be tape loops and EQ loops where you can tap for signal. The manual may have a Block Diagram you can copy and mark-up with observations. Same as you might sketch your house water plumbing and mark where you hit dry holes and where you made puddles.
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I've managed to make a little bit of progress this morning.
Using my PC as a sine wave test tone source I've been able to trace the signal with my oscilloscope to the volume pot.
The volume pot is mounted on a small PCB and I can trace the signal to a relay but not out of the other side of this relay.
So, I bypassed the volume control PCB completely and I could play a test tone from a speaker via the speaker terminals. 🙂
So my best guess is that I now need to try and understand if the relay is faulty or just not turning on to allow the signal to pass through.
Do you think the original intermittent fault could have been this relay failing and it just happened to fail completely after I rebuilt the amp?
Using my PC as a sine wave test tone source I've been able to trace the signal with my oscilloscope to the volume pot.
The volume pot is mounted on a small PCB and I can trace the signal to a relay but not out of the other side of this relay.
So, I bypassed the volume control PCB completely and I could play a test tone from a speaker via the speaker terminals. 🙂
So my best guess is that I now need to try and understand if the relay is faulty or just not turning on to allow the signal to pass through.
Do you think the original intermittent fault could have been this relay failing and it just happened to fail completely after I rebuilt the amp?
Since I don't know what I'm doing I tempted to take a punt and replace the relay in question.
The part number is DF2-DC5V from Matsushita (Panasonic). Unfortunately they're long out of production so a suitable replacement is my only option.
Can anyone help me select a suitable part? I'm a bit baffled by the specs. The datasheet for the original is available here:
https://www.panasonic-electric-works.com/pew/pl/downloads/ds_61002_en_df.pdf
The part number is DF2-DC5V from Matsushita (Panasonic). Unfortunately they're long out of production so a suitable replacement is my only option.
Can anyone help me select a suitable part? I'm a bit baffled by the specs. The datasheet for the original is available here:
https://www.panasonic-electric-works.com/pew/pl/downloads/ds_61002_en_df.pdf
Question is, does that particular relay operate at all? (Keep finger on it during turn-on.) If not, is there any voltage applied to the relay coil (multimeter time)? Relays can develop contact issues (in which case it still is possible to open and clean them in a lot of cases) but they very rarely totally fail. Bad electrolytics or transistors in the relay driver circuitry are more commonly seen, and finally the supply voltage may not be present for some reason. With some bad luck, you also created a solder bridge during resoldering which is now defeating the relay driver. This will have to be traced methodically.
Which relay is it, RY301 I guess? If so, does the red volume knob LED illuminate? Q310 is used to short out the relay coil and hence disable the relay in Source Direct. There may also be something wrong with signal routing in general. From the schematic, I don't really get where it runs with Source Direct on.
Which relay is it, RY301 I guess? If so, does the red volume knob LED illuminate? Q310 is used to short out the relay coil and hence disable the relay in Source Direct. There may also be something wrong with signal routing in general. From the schematic, I don't really get where it runs with Source Direct on.
Check the voltage on the relay coil, if this is OK, check the voltage on the output of the pre-amp and report back.
> DF2-DC5V
DPDT, non-latching, 5V 40mA
Not a tough spec to match.
If you are gonna trash it, first pry off the cover and work a piece of paper through the contacts. That may remove tarnish. And it may contaminate them with paper lint. But if it is now "dead", it is low-risk.
DPDT, non-latching, 5V 40mA
Not a tough spec to match.
If you are gonna trash it, first pry off the cover and work a piece of paper through the contacts. That may remove tarnish. And it may contaminate them with paper lint. But if it is now "dead", it is low-risk.
This piece of advice is late but will come handy...
First fix the problem, if possible with no or minimum dismantling.
Next make a video of the insides revealing all things clearly.
First fix the problem, if possible with no or minimum dismantling.
Next make a video of the insides revealing all things clearly.
Thank you all for the helpful advice. Here are some updates:
1) Yes the LED on the volume knob is illuminated.
2) Relay RY301 seems to be operating fine when the source direct switch is depressed.
3) Relay RY901 doesn't seem to be operating at all. There is no voltage at D933 and at the coil.
The bad news is that the speaker protection circuit is now activating after around 10 seconds 🙁
1) Yes the LED on the volume knob is illuminated.
2) Relay RY301 seems to be operating fine when the source direct switch is depressed.
3) Relay RY901 doesn't seem to be operating at all. There is no voltage at D933 and at the coil.
The bad news is that the speaker protection circuit is now activating after around 10 seconds 🙁
Thank you all for the help and advise, I'm delighted to say that the amp is now working.
The problem turned out to be a simple and stupid mistake I made when rebuilding the amp, I simply got two of the connectors mixed up!! So, the moral of the story is to take plenty of photos before taking things apart!
The amp now works perfectly apart from the small issue that the relay for the speakers A output is not functioning. Hopefully I just need to replace the relay. On speakers 'B' it works perfectly and sounds great.
I just need a replacement for the obsolete OMRON G5R-2232P-KW
The problem turned out to be a simple and stupid mistake I made when rebuilding the amp, I simply got two of the connectors mixed up!! So, the moral of the story is to take plenty of photos before taking things apart!
The amp now works perfectly apart from the small issue that the relay for the speakers A output is not functioning. Hopefully I just need to replace the relay. On speakers 'B' it works perfectly and sounds great.
I just need a replacement for the obsolete OMRON G5R-2232P-KW
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