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Faulty Naim CD player.

Luca

pfm Member
Hi all,

My Naim CDI needs repairing. It switches on and mechanically is fully working, immediately after the switch on it plays music for few seconds but then the NADI logo and the sound turn off (at the same time) and stay so until the switch off an on. When I turn on it again, it sounds for few seconds before muting.
Does anyone have an idea where the source of the fault may be?

Thanks in advance for the reply,
Luca
 
My CDI player worked properly for an year until I left it unused two months during this summer. Now if I turn it on the fault reoccurs.
Checking all the power supplies I’ve just found a problem around an LM337 (the one pointed in the image).

CDI_NAIM04 by Luca B, on Flickr

It has the same input voltage of the homologue LM317 but a lower output (-8.7 instead of -9.7V).
Before going to replace all the tants, I'm wondering if could one of them cause an higher drop out or might it depend on faulty LM337? Is there a kind expert who can help me with an answer to this question?
 
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That seems like a strange anomaly, maybe measure the biasing resistors across the reg and confirm the voltage you should expect.

Can you post a better close up picture of the regulator portion of the board?
 
Can we have a picture of the trace side so we can work out how its wired, suspect two of those resistors may be in parralel.


Brown Black Brown = 100R
Yellow Violet Red = 4K7
Gray Red Brown = 820R


Assuming the 4k7 and 820r are in parralel giving 698R the Output voltage should be 9.97V, Whats the supply voltage at the input to the reg?

Check the resistor values havent wandered and if they are OK , and the supply is OK, its new regulator time
 
ATMO, I have not yet desoldered and removed the circuit board so I cannot see and take a shot of the trace side. I hope to find time in next weekend. I took the first photo from the net.
 
This is probably caused by a leaky tant on the output of the LM337. If you're going to replace them anyway you can confirm this by snipping one of the legs.
 
This is probably caused by a leaky tant on the output of the LM337. If you're going to replace them anyway you can confirm this by snipping one of the legs.

Thank you for the hint. I'll let you know in the evening. Thanks all again!
 
Can we have a picture of the trace side so we can work out how its wired, suspect two of those resistors may be in parralel.


Brown Black Brown = 100R
Yellow Violet Red = 4K7
Gray Red Brown = 820R


Assuming the 4k7 and 820r are in parralel giving 698R the Output voltage should be 9.97V, Whats the supply voltage at the input to the reg?

Check the resistor values havent wandered and if they are OK , and the supply is OK, its new regulator time

You are right, two resistors are parallel.
Yesterday, I checked how the regulation circuit components are connected together

20210826_224411 by Luca B, on Flickr

but I had to stop my measuring (for a long work call) while I was testing the voltages on all three pins of the reg. The input voltage on the LM337 is OK. I will measure on the other two pins ASAP. The problem is due to either the adj or output capacitor (as MJS hinted).
 
Yes, leaky adj cap will act like extra shunt resistor (across 820//4k7) pulling the output low. As others have said, just replace the tants. You know it makes sense ;)
 
It's a nasty job changing all those tantalum beads. You need a very good solder sucker or desolder gun. Naim don't print component ID or orientation on the PCBs so you either have to mark them up or rely on the fact that all the regulators have 3 of them and they all tie to a ground rail. On the negative regs (337s) the positive side will be there and vice versa for the positive regs (317s). Beware that they like to move them around, especially near the transport, so it may not be obvious which regulator the tant next to it will be referring to. Buy more than you need, they sometimes go pop the first time, even when correctly orientated.
 


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