Nad 3140 Clean up and repair.

[Eastham]

Few days ago I plucked myself a non-working Nad 3140, seller described it as "nothing working".

Upon cracking it open I found quite a lot of dust and nasty, brown grease everywhere, cleaned the dust out with my hoover and a paint brush because I didn't fancy walking out in the rain to my shed where my air compressor is, I'm going to wait for a dry day to hose off the grease with PCB cleaner or something brake cleaner maybe?





All nice and clean.



Upon inspection I found some caps that look like they got very hot and some nasty glue that turned black... one was bulging and one of the 470µF 63V caps had vented.









Replaced all the bad caps I could with ones I had to hand and orderd the ones I need.



Now, onto the problem and what was causing it. I noticed with headphones I could hear faint signals with the amp turned up to max, seeing that both channels where effected I thought it was a pretty good chance it was a power supply issue, so I cracked out my multimeter and found I was missing the -21v rail for the pre-amp, a little probing around and I found a bad trace that was hidden by one of the chassis brackets, this trace connects R623 to R808 which feeds Q808 which regulates the -21v rail, bridged the two solder joints and she fired into life!



Cap deathtoll so far.



The blackend caps and the swolen cap all measured no capacity and I could actually measure resistance on them, 3Mohms on that swollen cap and 25 - 35Mohms for the blackend ones.

I could re-cap this unit but eh... Maybe later, sounds pretty fantastic right now, more updates when the rest of the caps come in.

 

[bradfro]

The 3140 is one of my favorite NADs. Easy to work on and with new caps sounds fantastic. Yours is a good example of the older NAD models, good design using cheap capacitors. I've restored 3 of these over the years. Interesting in that the older 3140's have T03 outputs and the newer models use the Sankin MT-200.

 

[Eastham]

The 3140 is one of my favorite NADs. Easy to work on and with new caps sounds fantastic. Yours is a good example of the older NAD models, good design using cheap capacitors. I've restored 3 of these over the years. Interesting in that the older 3140's have T03 outputs and the newer models use the Sankin MT-200.

View attachment 1360464

It really does sound good, I'm starting to fall for it... Mines the older one with the TO3 aswell. Mine also seems to have had the Adcom cartridge mod done, soft clip circuit is still the old transistor style so I may get some 22v zeners and perform that service bulletin mod too.

 

[Eastham]

So about the waiting for a dry day to clean the amp out, well.... I decided to do it now, So I removed the right hand side panel, proped it up on its side and blasted a can of deoxit on the boards, I know, that's not what it's for but it blasted a load of the oily substance off the boards, followed up with some IPA and brushing. Looks and smells WAY better.

 

[NAD80]

Love the 3140. Have one since new. I need to recap mine. Replace the pots with Bourns multi turn pots. Change the small .63mfd to 5mfd with Wima films where possible. Check out leesonic's threads on rebuilding NAD 3020's and other gear. When new I impressed a friend with how it sounded thru Snell Type A's. Using Denon TT, MC cart. Gotta watch that glue. It turns conductive as it goes dark brown/black.

 

[Eastham]

Love the 3140. Have one since new. I need to recap mine. Replace the pots with Bourns multi turn pots. Change the small .63mfd to 5mfd with Wima films where possible. Check out leesonic's threads on rebuilding NAD 3020's and other gear. When new I impressed a friend with how it sounded thru Snell Type A's. Using Denon TT, MC cart. Gotta watch that glue. It turns conductive as it goes dark brown/black.

Good advice! I'm not sure if I'll be re-capping it, it sounds pretty damn good as it is! I will be replacing those pot's though, setting the bias was like defusing a bomb, one µm turn to far 200mV... I've been scraping that glue off as I find it, so far I think I've gotten it all.

 

[NAD80]

Good luck with the 3140. Will want to hear how it turns out.

 

[Eastham]

Good luck with the 3140. Will want to hear how it turns out.

Thanks.

 

[Eastham]

Got bored, new caps haven't arrived yet so it may be tomorrow, decided to test one of the bad caps I pulled out of the power supply of this unit.

This used to be a lavender Matsushita 10µF capacitor, now it's a sh*t brown, baked Matsushita 100 megaohm resistor...

 

[Eastham]

Another little update, I noticed the power meters weren't working, quickly found a broken wire and had my suspicions verified, someone else had molested this device before me!

Broken wires



Broken solder pads.



So I re terminated the cable and did my best to clean things up.

 

[Eastham]

Even more cleaning! The amp still stank so I removed the heatsink to give it a deep clean.

Before, old, dried, nasty thermal paste.



Wires are supposed to be desoldered at the transistors, obviously I desoldered them at the board...





Gave the heatsink in some hot water with some detergent and a brush, smells so much nicer now. Re pasted with some Arctic Cooling MX-4 thermal paste.

 

[Eastham]

Rest of the caps came in yesterday so I got the old low voltage supply filters replaced, found some more bad glue and cleaned it up aswell, re-adjusted the offset and idle current and buttoned it up, sounds great and smells great to.

 

[Scott Frank]

Love the 3140. Have one since new. I need to recap mine. Replace the pots with Bourns multi turn pots. Change the small .63mfd to 5mfd with Wima films where possible. Check out leesonic's threads on rebuilding NAD 3020's and other gear. When new I impressed a friend with how it sounded thru Snell Type A's. Using Denon TT, MC cart. Gotta watch that glue. It turns conductive as it goes dark brown/black.

Hi. I'm doing a NAD 3140 restoration and want to replace the trimming resistor pots. When I go to Mauser to source them they don't have the same specs that are being called for in the service manual parts list.

Service Manual Parts List:

• VR601, VR602 - Semifixed "1KB"
• VR603,VR604 - Semifixed "500B" (Is this a typo? Should it be "KB" instead of "B"?)
• VR201, VR202 - Semifixed "200KB"

Mauser's resistance specs are in Ohms - nothing listed in KB. And the parts list doesn't specify the wattage - only "KB" and "B".

Do you have any information on the Ohm specs (and others) for the replacement trimming resistor pots?

Thanks for any help you can provide.

 

[Eastham]

Hi. I'm doing a NAD 3140 restoration and want to replace the trimming resistor pots. When I go to Mauser to source them they don't have the same specs that are being called for in the service manual parts list.

Service Manual Parts List:

• VR601, VR602 - Semifixed "1KB"
• VR603,VR604 - Semifixed "500B" (Is this a typo? Should it be "KB" instead of "B"?)
• VR201, VR202 - Semifixed "200KB"

Mauser's resistance specs are in Ohms - nothing listed in KB. And the parts list doesn't specify the wattage - only "KB" and "B".

Do you have any information on the Ohm specs (and others) for the replacement trimming resistor pots?

Thanks for any help you can provide.

Hi, the B stated on the parts specifies the type of resistance curve, B means linear, as far as I know all trimmers are linear the K means x1000 so 1k is 1000 so you're looking for timmers in these values.

1K ohm
500 ohm
200k ohm

Hope this helps!

 

[Scott Frank]

Hi, the B stated on the parts specifies the type of resistance curve, B means linear, as far as I know all trimmers are linear the K means x1000 so 1k is 1000 so you're looking for timmers in these values.

1K ohm
500 ohm
200k ohm

Hope this helps!

Terrific feedback. Thank you so much.

 

[Eastham]

Terrific feedback. Thank you so much.

No problem, best of luck with the resto!

 

[Audiobro]

Ugh! That assembly glue is the worst.

 

[Scott Frank]

Regarding a NAD 3140 restoration, can someone please educate me on what a "Dryal" capacitor is and how to buy them?

I can't find a description via search, and can't identify them on Mouser in the capacitor section. I'm specifically referring to the following part numbers from the service manual:

C531-C532 and C601-C604 - Dryal Capa. 1uF 16V

Thanks

 

[leesonic]

Regarding a NAD 3140 restoration, can someone please educate me on what a "Dryal" capacitor is and how to buy them?

I can't find a description via search, and can't identify them on Mouser in the capacitor section. I'm specifically referring to the following part numbers from the service manual:

C531-C532 and C601-C604 - Dryal Capa. 1uF 16V

Thanks

It's a solid aluminum electrolytic capacitor. Replace with a Nichicon KL, or a film cap if you so desire.

Lee.

 

[Scott Frank]

It's a solid aluminum electrolytic capacitor. Replace with a Nichicon KL, or a film cap if you so desire.

Lee.

Thanks Lee. I can't find a Nichicon UKL 1uF 16V (or even a 50V) that's in stock at Mouser or DigiKey. And can't seem to be able to identify an appropriate film cap either. Would you happen to have another suggestion?

Also, given this type of capacitor (low leakage current) should I even be worrying about replacing it? I'm assuming they age like a typical audio grade capacitor but that may not be the case...

Scott