advertisement


Naim CDI no sound output

Find the data sheet for the reed relays and just bypass the audio switch pins with a bit of wire from above the pcb ,they are trouble some, when you get it working bob some new ones in as part of the service.
 
martin clark said:
The TDA1541A dac is current-output, so you won't see AC voltage on its outputs; that's the job of the I-V converter on each channel, which is the pair of OP42 opamps immediately adjacent to the dac - with a very handy ground point adjacent were several wires meet.

The output signal voltage appears on pin 6 of each - counted relative to the notch on the opamp body:
8pin%20dip.jpg


So - clip the scope probe ground wire to the ground point, checking you get continuity onto the bare wire stub
  • Set the scope to a vertical sensitivity of something like 1V ac / division and a timebase of maybe 1mS/ horizontal division
  • Set a CD playing
  • Carefully with the probe set at' x1' - probe pin 6 on each of the two opamps.
  • Check to see if you are getting music out of the dac..! which will be a recognisable jumble of waveforms of nearly 3v pk-pk.at each .
If so - then the dac is working, and the problem lies downstream; since the problem affects both channels, it's the muting relay/ its drive circuit.

Feint hope, but I wouldn't want you to tear-into removing the dac without testing it is not delivering first. The PCB tracks on these are getting fragile.
Click to expand...
Thanks for that suggestion Martin, that sounds like A Cunning Plan! I shall do just that. VERY much a newbie with an Oscilloscope, so will read up about changing the vertical sensitivity and the timebase first. The Rigol seems to have a pretty decent manual fortunately.

Yes was quite disappointed in the quality of the PCB to be honest. Though managed to replace 53 tantalum caps without any lifted traces, but it was very time-consuming and delicate work. Agreed (muchly) about not taking out the TDA until it's 100% certain it's a Dead Parrot.
 
hp1 said:
Find the data sheet for the reed relays and just bypass the audio switch pins with a bit of wire from above the pcb ,they are trouble some, when you get it working bob some new ones in as part of the service.
Click to expand...

The relay's may well all be fine, and I fortunately have spares from a different Naim project a while back, but ta for the suggestion.
 
John_73 said:
Thanks for that suggestion Martin, that sounds like A Cunning Plan! I shall do just that. VERY much a newbie with an Oscilloscope, so will read up about changing the vertical sensitivity and the timebase first. The Rigol seems to have a pretty decent manual fortunately.
Click to expand...

John,
A great Primer on learning what you can do with an oscilloscope, remains Tektronix' classic ' XYZs of oscilloscopes'

I've posted a copy here:

ATB!
 
Rip test CD with sine waves from youtube . It's easier to test than with music signal. Less confusing.( taking a break from re-caping Ole Nait 5:)
 
Good point - I've generated a range of test tones at -10dB which form a compact zip archive I can post if anyone wants to write themselves a test CD.
 
Martin , Last off topic post , I promise:)
I've got a senior moment when undertaking Nait 5 re-cap and didn't measure the bias on the amp before the re-cap. Now after the re-cap the bias started from cold 3.4V to 2.5V after 20 min. Both channels track perfectly. I assume it should be something around 5mV on "new Naim" amp , correct ?
No wonder that the amp was reported the most round earthed from the lineup. All audio coupling is done via Elna 10uF/35V el cap. Straight from DIN connectors signal goes through Elna and on every stage there is Elna as a coupler. I have boards from Denon HT receiver with the same Elnas. Not a bad cap apparently.
 
Pirx said:
Rip test CD with sine waves from youtube . It's easier to test than with music signal. Less confusing.( taking a break from re-caping Ole Nait 5:)
Click to expand...

martin clark said:
Good point - I've generated a range of test tones at -10dB which form a compact zip archive I can post if anyone wants to write themselves a test CD.
Click to expand...

I posted a link to a page of test tones a page back : https://www.wavecor.co.uk/testdisk.html

Unfortunately my CDI doesn’t seem to read CD-Rs, as tried burning the 1khz test tone to a disc. Burned at x4 speed, can’t burn at a lower one alas with my drive. I guess I should check & reset the laser current etc. (did this before on my first CDI when I replaced the laser) a bit later, but for now will see if the TDA is OK following your advice.
 
Right-o, will have a think later... though I don't think its shows anything much like good news (initial impression, sadly - but yet to get my head around the Rigol screen display and markers; I'm still a 'reach for the Tek 475A' sort of person...)
 
martin clark said:
Right-o, will have a think later... though I don't think its shows anything much like good news (initial impression, sadly - but yet to get my head around the Rigol screen display and markers; I'm still a 'reach for the Tek 475A' sort of person...)
Click to expand...

I’ll try and take those measurements again tomorrow at any rate, this time at x1 as you suggested earlier, and will try flexing the pcb gently too.
 
Later today I’m going to temporarily solder in the components to try the spdif test and plug it into an external DAC, to see if the saa7220 is OK.

If that works, does that mean the saa7310 is fine too, or will that need testing also? Want to try everything (within my means anyway) before desoldering the TDA1541. I do have a Duratool desoldering gun and have plenty of experience desoldering ICs, so shouldn’t be a problem there other than the pin connected to the large ground plain.
 
You must log in or register to reply here.


advertisement


Back
Top