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Deltec Precision Audio (DPA) - Little Bit DAC

gidders

gidders

hifi enthusiast, golfer & photographer
I have one of these DACs (not sure if it’s a Mk 1 or 2) and the right output channel has died.

I've had a quote but at the figure quoted it's not really economically viable but I'm reluctant to throw it in the bin

Anyone here have the skills to repair it & if so how much?

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@barryblue - good call!

One channel dropping is unusual; the reservoir caps (usual point of failure in these) and voltage regulators are shared between the channels; and the SAA73xxx DAC is a low-power part, good and reliable. So are teh output opamps - NE5532 iirc.

So it tend to be the whole 'goes off' not one side only. NB the fact you get sound out of one also means the entirely of the input receiver circuitry - everything on the right-hand-side of the picture- is running just fine. That's quite a saving on time.

So it has to be something simple; and a 'sticky' relay given it is easily 30yrs old, is an excellent suggestion - also relatively-simple fix.

(and @gidders - you are right: too nice to just bin
I've worked on a lot of DPA/ have ...at least one of these known-good, so will help if I can)
 
Pretty sure (it was a long while back) my old one had the relay being an issue too. Also worth a quick check to see if the direct soldering of the RCA socket to the pcb has fractured on one side.

Great sounding dac, even now.
 
@gidders

Looking as closely as I can at the posted photo - you see that output phono socket on the bottom- left of the picture?
Is that the Right channel output?

If so - check the centre-pin connector solder joint hasn't cracked where it joins the PCB: it looks wrong, compared to the other one.

(In these dacs, and some of the pre-amps - these take an awful lot of abuse with tight-fitting phono plugs, because thay are only held in place with the solder! very, very easy fix if so... obvs been @John_73's experience, too)
 
Are those RCA connectors actually original?

They are clearly chassis mount connectors which have been bodged into a space where a PCB mounted connector ought to go.

If they are why did they make it like that?
 
Thanks for the input guys

barryblue said:
Have you tried tapping the relay (white rectangle between the RCA connectors) lightly with a non metal screwdriver handle or equivalent?
Click to expand...
@barryblue do I do this with the unit powered on or off?

martin clark said:
Looking as closely as I can at the posted photo - you see that output phono socket on the bottom- left of the picture?
Is that the Right channel output?

If so - check the centre-pin connector solder joint hasn't cracked where it joins the PCB: it looks wrong, compared to the other one.
Click to expand...
@martin clark I think it's just the angle of the photo - it tests OK
 
Re: the relay - hook it up, play music at low volume, and tap the relay while playing - in all three axes; though side-to side as pictured is likely the one that might un-stick things.
 
gidders said:
Thanks for the input guys


@barryblue do I do this with the unit powered on or off?


@martin clark I think it's just the angle of the photo - it tests OK
Click to expand...
Be wary - if that was you, pressing your dvm probe down on the exposed contact however-lighlty, might mean nothing....
Use the dvm probe just into the centre pin contact from rear panel direction, to be sure.

In any case- it's trivial, to re-flow the centrepin: pcb solder connection. Use leaded solder, and fairly chunky soldering iron of 20w+ if you have one (so it only takes a moment)
 
That's a fab result, at the right price!


TBH - best exercise would be just to switch the unit on & off as you use it, over the next few days, just to ensure the relay is exercised regularly.
If it still remains sticky to the point of annoying - then, ..you might just be able to wiggle the white cover off, and dose with a very little isopropryl alcohol. Or drill a tiny hole in the white cover, for ditto - while researching modern drop-in equivalents from the part number.

Enjoy your lovely Dac meanwhile!
 
gidders said:
Yay! Thank you to @barryblue & @martin clark - tapping the relay got the channel working again 😁

Should I replace the relay or just see how it goes? If replace - where would I get one or would I have to substitute? If so what with?
Click to expand...
Well done 😀

It seems the STC relays are still available, one source here......
www.ebay.co.uk

3x STC 51SB24T , DUAL LINE POWER RELAY 24.0VDC , T.H. 8-PIN | eBay

3 PCS x STC 51SB24T . DUAL LINE POWER RELAY 24.0VDC, T.H. 8-PIN.
www.ebay.co.uk

Are you okay at soldering? If not feel free to message me.

Barry
 
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This site contains affiliate links for which pink fish media may be compensated.
One more suggestion - while you have this in pieces, replace the two reservoir capacitors next to the transformer. They are marginally -rated, at only 25Vdc (when they'll be running at 24-25vDC...) and 85degC, and will cook out eventually.

Modern 105degC/ 1000 or even 2200v parts will fit and give it a new lease of life. Stick with basic good quality industrial parts, Panasonic or sim.
 
Thanks for the suggestion @martin clark but this...
martin clark said:
Modern 105degC/ 1000 or even 2200v parts will fit and give it a new lease of life. Stick with basic good quality industrial parts, Panasonic or sim.
Click to expand...
might as well be in arabic :confused: Please can you point me at exactly the caps I could replace them with ? 🙏
 
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