Looking at the schematic again, it look like that cap has around 20-21v across it since it returns to the negative rail. In that case even using a 25v rated part might be cutting it pretty close.
OK so with the new capacitor, the problem is reintroduced. If I remove the new capacitor, it works absolutely fine. Plays back audio through both channels beautifully.
Any ideas?
Am I going to cause damage if I just leave the cap out...?
Any ideas?
Am I going to cause damage if I just leave the cap out...?
Is the regulator output voltage still present with the capacitor installed? Or, is the cap causing the regulator output voltage to change? If the output is dropping down close to the -14v rail then the new cap may be installed backwards or it may be defective. If the regulator is oscillating, then its likely the wrong cap.
The cap values are the same as the old one, and it's installed with the same polarity (according to the tiny little + marking on the cap).
I'll disassemble it again and measure as above. In the meantime do you think leaving the cap out will cause any damage? It functions perfectly without it. How strange.
I'll disassemble it again and measure as above. In the meantime do you think leaving the cap out will cause any damage? It functions perfectly without it. How strange.
Also I'm still getting an occasional static/crackling through the output which seems to come and go if I press on the PCB of the digital board (it's inside a shielded container).
I thought it might be a bad solder joint but I've resoldered a lot of it and it still seems to do it.
SONY DAS-702ES SM Service Manual download, schematics, eeprom, repair info for electronics experts
Service manual is here if anyone has any bright ideas 🙂
I thought it might be a bad solder joint but I've resoldered a lot of it and it still seems to do it.
SONY DAS-702ES SM Service Manual download, schematics, eeprom, repair info for electronics experts
Service manual is here if anyone has any bright ideas 🙂
The + side of the cap should go as shown on the schematic, towards pin 18 of the dac chip and pin 2 of the regulator. If that is correct, then does pin 18 of the dac chip measure about +5.7v to ground with or without the cap in place?
Leaving out the cap could cause the regulator to become unstable. That is to say, it might ring or oscillate. However, using the wrong type of cap could possibly have a similar effect. You need a scope if you want to diy it more properly.
Regarding the crackling, sure sounds like what one might expect from a bad connection, including possibly one inside a component. Probably best to focus on one thing at a time though. If you want to go looking for the crackle source, first thing is to note if it only affects one channel or both? Does it go up and down with the volume control? Does it happen for one or multiple of the digital inputs, etc.? In other words, start narrowing down the search using a little common sense if at all possible. It might be necessary to remove the board and inspect it carefully with a magnifying glass (might have to clean it off a little first). If simple measures don't narrow it down to a very small number of possibilities, there is always freeze spray which occasionally helps. A more desperate approach might be to bend and flex the board more vigorously (with power off) to see if you can make it fail completely. Its always easier to diagnose something that is fully broken rather than something vexingly intermittent.
Leaving out the cap could cause the regulator to become unstable. That is to say, it might ring or oscillate. However, using the wrong type of cap could possibly have a similar effect. You need a scope if you want to diy it more properly.
Regarding the crackling, sure sounds like what one might expect from a bad connection, including possibly one inside a component. Probably best to focus on one thing at a time though. If you want to go looking for the crackle source, first thing is to note if it only affects one channel or both? Does it go up and down with the volume control? Does it happen for one or multiple of the digital inputs, etc.? In other words, start narrowing down the search using a little common sense if at all possible. It might be necessary to remove the board and inspect it carefully with a magnifying glass (might have to clean it off a little first). If simple measures don't narrow it down to a very small number of possibilities, there is always freeze spray which occasionally helps. A more desperate approach might be to bend and flex the board more vigorously (with power off) to see if you can make it fail completely. Its always easier to diagnose something that is fully broken rather than something vexingly intermittent.
Last edited:
So a bit of an update. I'm still trying to diagnose the digital noise/static caused by the digital board.
If you look on page 18 of the service manual, I have narrowed the issue down, I think, to the bottom right area of the board - that is the "VCO Block" area with IC522 and others.
If I press on the board around here when the noise is present, it usually stops.
I can affect the noise by probing the "osc" pin of the VCO block with a screwdriver/multimeter pin/whatever.
If I measure the voltages of the chip IC522 the sound changes.
Pins 1 and 6 of IC522 should be 1.5 and 1.6V but I'm measuring around 2.3V.
I'm assuming this isn't right.
Any idea what might cause this? Is the resistor R506 responsible for lowering 5V to this voltage?
Thanks very much!!
If you look on page 18 of the service manual, I have narrowed the issue down, I think, to the bottom right area of the board - that is the "VCO Block" area with IC522 and others.
If I press on the board around here when the noise is present, it usually stops.
I can affect the noise by probing the "osc" pin of the VCO block with a screwdriver/multimeter pin/whatever.
If I measure the voltages of the chip IC522 the sound changes.
Pins 1 and 6 of IC522 should be 1.5 and 1.6V but I'm measuring around 2.3V.
I'm assuming this isn't right.
Any idea what might cause this? Is the resistor R506 responsible for lowering 5V to this voltage?
Thanks very much!!
Looks like IC522 is a JK flip flop that can be seen in the schematic at the bottom center of page 18 of the PDF service manual (page 26 of the original paper document). On the schematic it follows the VCO.
That would seem to suggest a scope should be used to look at the clock pulses as they are generated and processed along though that section of the circuitry. Do the pulses get lost at some point in the clock signal flow as the board being is gently flexed?
That would seem to suggest a scope should be used to look at the clock pulses as they are generated and processed along though that section of the circuitry. Do the pulses get lost at some point in the clock signal flow as the board being is gently flexed?
I don’t have a scope unfortunately. I am guessing this is getting beyond my abilities if there are things that need checking I can’t use my DMM for!
🙁
🙁
This node in the circuit is a high impedance point (two 1Mohm resistors, one to each rail). So the voltage you see will depend to a large degree on the loading your meter places on it. I'm assuming you've read the service manual - does it stipulate the characteristics of the meter to be used? An infinite input impedance meter would show 2.5V at this point, some DMMs do have extremely high input impedance (10Mohm or more) on their lower voltage ranges if memory serves. [Note that pin 1 and pin 6 are connected together so different voltages on each is nonsensical - they might reflect different meters being used to register the two reported voltages]
R506 in conjunction with its partnering resistor R557 yes.
Thanks, so probably a red herring then. The SM says nothing about the type of meter to use that I can see.
Any idea where I can go from here without a scope?
OK so here's an unusual development...
I was moving the coax input cable around and noticed the noise change its form slightly as I was doing it.
So I wondered if there's some grounding/mains noise issue going on.
I have a datacentre-grade UPS powering my home networking equipment which is in the same room, so I decided to power the DAC from that.
Silence. Just beautiful music if I play it.
Approx. 3 hours later, still silence.
I then dug out an old Tacima mains filtering power strip which I remembered I had, and plugged it into that. 1.5 hours later, still silent.
Since the DAC isn't earthed (in the UK we have 3-pin plugs with an earth, and it's double-insulated meaning the casing isn't earthed) I guess it can't be an earth loop issue, so I guess noisy mains, either my amp/cd player/USB DAC, or something somewhere else?
Is it possible the somewhat ageing power supply section in the DAC (capacitors) is now unable to filter out mains noise, possibly caused by modern cheap nasty switching power supplies?
I wondered about earthing the chassis anyway, but I'm not sure that's a) a good idea or b) it will help.
Any other explanations?
I was moving the coax input cable around and noticed the noise change its form slightly as I was doing it.
So I wondered if there's some grounding/mains noise issue going on.
I have a datacentre-grade UPS powering my home networking equipment which is in the same room, so I decided to power the DAC from that.
Silence. Just beautiful music if I play it.
Approx. 3 hours later, still silence.
I then dug out an old Tacima mains filtering power strip which I remembered I had, and plugged it into that. 1.5 hours later, still silent.
Since the DAC isn't earthed (in the UK we have 3-pin plugs with an earth, and it's double-insulated meaning the casing isn't earthed) I guess it can't be an earth loop issue, so I guess noisy mains, either my amp/cd player/USB DAC, or something somewhere else?
Is it possible the somewhat ageing power supply section in the DAC (capacitors) is now unable to filter out mains noise, possibly caused by modern cheap nasty switching power supplies?
I wondered about earthing the chassis anyway, but I'm not sure that's a) a good idea or b) it will help.
Any other explanations?
Well, guess I would respond by saying that high quality power conditioners can help clean up the sound of good hi-fi systems more than one might expect. Personally, I use a 2nd hand Monster HTPS 7000 MkII from ebay. My high end audio designer friend uses an old PS Audio Regenerator for his stereo. Those are two of best choices available, maybe THE best, at least to my knowledge.
Another thing that I found interesting, the above power conditioner also cleaned up an intermittent frying noise in my tube guitar amp that I never quite figured out the source of until then. However, another popular brand of power conditioner for audio systems that I tried didn't help at all.
Another thing that I found interesting, the above power conditioner also cleaned up an intermittent frying noise in my tube guitar amp that I never quite figured out the source of until then. However, another popular brand of power conditioner for audio systems that I tried didn't help at all.
Interesting!
So this is a plausible cause for digital noise which sounds like a poor lock onto an SPDIF stream, created within the digital board of the DAC?
So this is a plausible cause for digital noise which sounds like a poor lock onto an SPDIF stream, created within the digital board of the DAC?
If the effect of moving a ground or other power connection is very repeatable then probably not random chance nor your imagination.
Hmm, turns out it was a fluke I guess.
The DAC was on for hours this afternoon (presumably fully warmed up) and playing music happily without any static, while plugged into the mains conditioner.
Turned it on this evening after being off for a couple of hours and the static is back. Will be interesting to see how long it lasts.
How infuriating.
The DAC was on for hours this afternoon (presumably fully warmed up) and playing music happily without any static, while plugged into the mains conditioner.
Turned it on this evening after being off for a couple of hours and the static is back. Will be interesting to see how long it lasts.
How infuriating.
Hello Howard, did you manage to repair your 702es ? I have one that's developed a fault and I would like to get it fixed, it's beyond my skills, any ideas /cotacts please ?
regards
Alan
regards
Alan