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Naim HiCap2 - one output too high

_webwasher

_webwasher

pfm Member
One output is 24 (ok I guess) and the other 29V. All caps measure ok, so do the resistors of the ok channel.
The resistors of the defective channel and resistance between the connections of the voltage regulator measure strange as if the regulator has been damaged.

What could have happened? And how to fix it?

Thanks for reading.
 
Resistors actually being off value would be fairly unusual unless they have actually been changed for incorrect values. It should be obvious if that is the case since the colour codes will be different from the ones on the working side.

If that's the issue then the fix is to reinstate the correct values.

If it isn't then the 317 will need to be replaced. They are no longer manufactured but NoS or used ones are fairly easy to come by. I'd avoid anything from Chinese Ebay vendors since it's highly likely to be fake.

Naim used to test them for noise but in practice the vast majority passed in later years so anything of recent manufacture is likely to be OK. You could be extra safe by getting a used Naim regulator board. They are also fairly easy to come by due to TPR4 and Dragon Newt upgrades.
 
Many thanks. Colour code of resistors is identical for both channels. Then most likely the 317 as you describe. Should they be changed as pairs or just the faulty channel?

Tants measure ok but I’ll do as Martin suggest 👍
 
Good point, tants are the most likely failure point, but they tend to go black or explode so it's pretty obvious in most cases.

Sensible to change them first anyway because it's cheap and easy.

For no obvious reason Naim stopped fitting the protection diodes in the late 90's which makes it a lot easier to kill the regulator by short circuit, though in practice they're more likely to fail to zero volts output.
 
_webwasher said:
One output is 24 (ok I guess) and the other 29V. All caps measure ok, so do the resistors of the ok channel.
The resistors of the defective channel and resistance between the connections of the voltage regulator measure strange as if the regulator has been damaged.

What could have happened? And how to fix it?

Thanks for reading.
Click to expand...
Just send it to Naim to get it fixed
 
And actually you could probably replace all of the components on one channel of the reg board for less than the cost of postage, with reasonable confidence that it would be fixed.
 
The tants failing will only cause the regulator voltage to go down. If all the resistors check out then it's the regulator, pure and simple.
 
Thanks MJS. All resistors checked yesterday - they measure ok and same values on both channels (with little tolerance of course).
So - now I’m searching for one (or better two to have an equal pair…) of Naim tested lm317. Anyone?
 
No luck required really.

For those with money to burn......


Pretty much guaranteed to be the real thing and a perfect visual match to your other one.

Cricklewood and Little Diode also claim to have NoS at much more sensible prices but I'd be less confident that they were genuine.

For the rest of us there's used and NoS of uncertain provenance

Used - and pretty much guaranteed to be genuine

www.ebay.co.uk

LM317K TO3 Voltage Regulator PCB inc Diodes Pots Fuse Holders etc. MBE019 | eBay

2 x 5401 diodes. Air Call Ltd Digital PCB. Each PCB contains…. 3 x 20mm fuse holders (inc fuses). Load Regulation: 0.5 %. Output Current: 1.5 A. resistors, capacitors etc. Series: LM317.
www.ebay.co.uk

There seem to be plenty of these old BT boards about. You could possibly even ask them to look you out a national semiconductor reg to visually match the one you have

NoS which looks like it might well be real (but also suspiciously cheap)

www.ebay.co.uk

X2 LM317K VOLTAGE REGULATOR | eBay

LM317K VOLTAGE REGULATOR. <br> <br>ALL EX RS STOCK <br>UNUSED & UNTESTED <br>BOUGHT IN BULK AND BEEN IN STORAGE <br>RRP DISCONTINUED <br>FOR PRODUCT SPECIFICATIONS USE MFR NUMBER ON GOOGLE.
www.ebay.co.uk

I'd be tempted to grab the two of those and hope what you get matches the picture unless somebody on here comes up with one.
 
This site contains affiliate links for which pink fish media may be compensated.
colasblue said:
No luck required really.

For those with money to burn......


Pretty much guaranteed to be the real thing and a perfect visual match to your other one.

Cricklewood and Little Diode also claim to have NoS at much more sensible prices but I'd be less confident that they were genuine.

For the rest of us there's used and NoS of uncertain provenance

Used - and pretty much guaranteed to be genuine

www.ebay.co.uk

LM317K TO3 Voltage Regulator PCB inc Diodes Pots Fuse Holders etc. MBE019 | eBay

2 x 5401 diodes. Air Call Ltd Digital PCB. Each PCB contains…. 3 x 20mm fuse holders (inc fuses). Load Regulation: 0.5 %. Output Current: 1.5 A. resistors, capacitors etc. Series: LM317.
www.ebay.co.uk

There seem to be plenty of these old BT boards about. You could possibly even ask them to look you out a national semiconductor reg to visually match the one you have

NoS which looks like it might well be real (but also suspiciously cheap)

www.ebay.co.uk

X2 LM317K VOLTAGE REGULATOR | eBay

LM317K VOLTAGE REGULATOR. <br> <br>ALL EX RS STOCK <br>UNUSED & UNTESTED <br>BOUGHT IN BULK AND BEEN IN STORAGE <br>RRP DISCONTINUED <br>FOR PRODUCT SPECIFICATIONS USE MFR NUMBER ON GOOGLE.
www.ebay.co.uk

I'd be tempted to grab the two of those and hope what you get matches the picture unless somebody on here comes up with one.
Click to expand...
Nice update, thanks for that ..and ...ouch!

I could build several really-good regulators dead-bug style, for far less ;)
 
This site contains affiliate links for which pink fish media may be compensated.
Good morning all,

Just a couple of what should be UBG TO3 LM317's:-

6evROjL.jpg


Regards

Richard
 
If your reg really is dead (which I would say is the least likely of all the components in the circuit), you could use one of the eye-wateringly expensive LM350Ks that RS sell I reckon.

Texas Instruments LM350K STEEL/NOPB , 1 Linear Voltage, Voltage Regulator 3A, 1.2 → 33 V 3-Pin, TO-3 | RS

uk.rs-online.com uk.rs-online.com

I've had my hi-cap fail on me twice (it actually uses TO220 LM317s) and both times it's been a tant.

It never ceases to amuse me that Naim's crazy-expensive (and surprisingly effective) pre-amp PSU uses one of the cheapest and nastiest ancient Vregs!
 
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