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No sound output from a DAC - any simple checks I can do?

S

starbuck

pfm Member
I have an old Woodside DAC here with no audio/sound output when connected to an amp. The 'Lock' light on the front illuminates so it seems to be getting a digital (coaxial) signal from the CD transport but no music.

My DIY skills are limited to basic soldering/de-soldering and I don't have any measuring tools beyond a digital multimeter, I was just wondering if there is anything straight forward I could check to see what the issue may be (beyond physically inspecting connections at RCA sockets > board)? It has a Philips S1 crown TDA1541A DAC chip and I would quite like to hear it/use it, if I can get it working.
 
Has it been connected and working recently and then failed in place? Or has it just been connected and found to not be working?

Knowing this kind of detail might help rule out user error.
 
Just connected and found to be not working. I hope to have enough knowledge of using a DAC to be able to rule out user error, though I cannot absolutely guarantee it :).
 
Take the lid off and post a photo here, someone may spot something obvious. Check for obvious things like broken connections/cables. If there are relays on the output fingers crossed they have just become stuck and there's nothing more serious at play.
 
I think the light grey coloured STC blocks are relays. When I get a chance to connect it up again, is it worth carefully tapping these relays whilst playing a CD to see if anything 'loosens up' if they have beome stuck?
 
Those white blocks are relays - you should hear a click I imagine after a few seconds once switched on. If there's no audible click I reckon they are both stuck. You could try tapping them, but I wouldn't do it with anything connected. Would be an easy enough job to replace them.
 
The relays are a prime candidate and if you had an oscilloscope it'd be dead easy to check.

Those tantalum beads would also be a prime candidate.

Do you have a voltmeter?
 
I have a Woodside WS3 CD player that has a similar DAC section. Mine also had no sound out - after seeing someone with the DAC only version gad problems with the GL399 chip (one by the output RCAs) I just ordered and replaced that as a first step. Nope! Mine was a failed TDA1541 - the -5v rail was sitting at -10v, suggesting something failed internally on the chip...and yes, it was an S1 too :(

My original thread here - I would carefully check if you can see/hear/feel/measure the relay activating. Maybe download GL399 chip data sheet and make sure it's trying to activate the relay.

But I'd also check you've got -5v on pin 26 of the TDA as a first step. Download the data sheet and check the other power rails (+5 and -15 too I think).

Definitely fixable, and worthwhile doing so - after fitting a Flea to my WS3 it is a wonderful player...beaten by the CDI with similar mods, but could easily live with it. If you get really stuck send it to me and I'll fix it...but I'm in Swissieland, so not very practical :) Good luck

Edit to add: I must still have the original GL399 chip somewhere if that's suspect, and you get stuck finding a replacement...no idea where, so may take a while to find :)
 
Mike P said:
The relays are a prime candidate and if you had an oscilloscope it'd be dead easy to check.

Those tantalum beads would also be a prime candidate.

Do you have a voltmeter?
Click to expand...

Thanks for the replies. I have got it back out and given the relays a couple of taps each before connecting it back up to try; still no music and no signs of any audible clicks from the relays.

I have a 'Precision Gold WG022' multimeter which can measure DC voltage - not sure how accurately in comparison to more expensive meters but it has been okay for me so far -, though I would need guidance as to where to stick the probes in order to take any measurements.

Dowser said:
My original thread here - I would carefully check if you can see/hear/feel/measure the relay activating. Maybe download GL399 chip data sheet and make sure it's trying to activate the relay.

But I'd also check you've got -5v on pin 26 of the TDA as a first step. Download the data sheet and check the other power rails (+5 and -15 too I think).

Definitely fixable, and worthwhile doing so - after fitting a Flea to my WS3 it is a wonderful player...beaten by the CDI with similar mods, but could easily live with it. If you get really stuck send it to me and I'll fix it...but I'm in Swissieland, so not very practical :) Good luck

Edit to add: I must still have the original GL399 chip somewhere if that's suspect, and you get stuck finding a replacement...no idea where, so may take a while to find :)
Click to expand...

Thanks for the suggestions (and offer too: much appreciated). Is measuring the pin you mention something that can be done with it in circuit on the board, and, if so, which is pin 26 and assuming I put one of the multimeter probes on pin 26, where does the other multimeter probe go?

As you can probably tell with me asking this, I am no expert, though am competent enough not to go grubbing around inside the case with power applied and would only carefully use the probes on the multimeter.
 
Clip the black/negative terminal to the metal casework of the DAC and then touch the red/positive probe to pins of the DAC.

Pin 28 should be about 5v
Pin 15 about -15v
Pin 26 about -5v

Be accurate about placing the probe and not to let it slip!

The numbering of the pins starts to the left of the notch are goes counter clockwise.
 
Better still, do as David suggests and check all the regs.

If in doubt, best give it to someone else to check.
 
Looking at the scorch marking the capacitor next to it, my money is on the regulator with the heat sink attached.

When measuring voltages just put the negative probe to chassis, the screw at 6 o’clock would work.
 
Dowser said:
I have a Woodside WS3 CD player that has a similar DAC section. Mine also had no sound out - after seeing someone with the DAC only version gad problems with the GL399 chip (one by the output RCAs) I just ordered and replaced that as a first step. Nope! Mine was a failed TDA1541 - the -5v rail was sitting at -10v, suggesting something failed internally on the chip...and yes, it was an S1 too :(

My original thread here - I would carefully check if you can see/hear/feel/measure the relay activating. Maybe download GL399 chip data sheet and make sure it's trying to activate the relay.

But I'd also check you've got -5v on pin 26 of the TDA as a first step. Download the data sheet and check the other power rails (+5 and -15 too I think).

Definitely fixable, and worthwhile doing so - after fitting a Flea to my WS3 it is a wonderful player...beaten by the CDI with similar mods, but could easily live with it. If you get really stuck send it to me and I'll fix it...but I'm in Swissieland, so not very practical :) Good luck

Edit to add: I must still have the original GL399 chip somewhere if that's suspect, and you get stuck finding a replacement...no idea where, so may take a while to find :)
Click to expand...

Yes sadly the S1 in my Naim CD3 also died so feel your pain
 
Or download the datasheet for the 1541, it shows the pin layout…and as per Mike, do not let the probe slip between pins :)
 
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