NAD 314--repair or not

[vineyridge]

I'm the only owner of this integrated amp, so I know its history. I used it exclusively for vinyl with a set of Spica TC50 speakers, ast of KEF C15s, a Dual CS5000 turntable and a Linn cartridge--forget the model--and mostly listened to all kinds of non-rock music.

Then I went through a long period of not wanting to listen. Now I do.

When I went to turn the amp on after two or three years of silence, it was dead. I figured that it had blown a fuse and would be a cheap repair. Not so. The repair shop says it needs a new set of MOSFETs on the output side at a cost of $275 US, plus $75 of labor. Says that a power surge, which happens often here, even with surge protectors, might have killed it--the surge protector might have died as well from overuse.

Is it worth repairing just for the phono stage and the fact that I'm the original owner? I can find the same model on Audiogon for much less, but don't know their histories. There's one for $250, and one for $150, both SAID to be in good working condition.

Advice, please.

[davetruestory]

For $400, you can get Nad 326BEE that its the new 314.

[vineyridge]

It's the built in phono stage (RIAA) (?) that I'm worried about finding in current amps. The phono stage on this one got excellent reviews and produced very good sound for me.

My listening would be vinyl.

[Cornelius900]

I would go and look for another repair shop, or use the amplifier as a pre-amp stage only.

This amplifier uses the mosfet type 2SC3519/2SA1386, these won't have to cost $250 to my opinion.

[Dr Pan K]

if i remember correctly this nad has a pre out. if so check if it actually works, using any given power amp and then buy yself a new nad power amp. u will get the same phono u like with more power to drive y speakers

[Cornelius900]

yes, is has a pre-out. And if my information (service manual) is correct, these transistors are not MOSFET, but bipolar transistors (NPN/PNP)

service manual can be found here:
[url]audio-circuit.dk[/url]

[Ldg]

The repair shop says it needs a new set of MOSFETs on the output side at a cost of $275 US, plus $75 of labor. Says that a power surge, which happens often here, even with surge protectors, might have killed it--the surge protector might have died as well from overuse.....Advice, please.

Hmmm. Well, the 314 doesn't use MOSFETs in the output stage, plus the output stage is fed from a regulated supply, so insulated from external surges to a fair extent. Plus, it's pretty unusual for both sides and all devices to fail. So, on this basis, I really doubt the repair shop's diagnosis. In any event, the output devices are not exotic, c $5 retail, so something seems pretty odd......

IMO the amp is well worth a repair, and it should be easy and hopefully cheap since the unit is dead. I'd suggest taking it somewhere else, to another repair shop.

[Cornelius900]

can you check what does work and what not?

For example, when it powers on, does the headphone output work?

[vineyridge]

When I say "dead", I meant DEAD. It wouldn't even power on. The green light never glowed. That's why I was assuming a blown main fuse.

[Alec124c41]

Check continuity in the power cord.

Cheers,
Alec

[rhomanski]

Most shops have learned their limitations and when you bring in something that they can't or don't want to fix, they will lie to discourage you. The problem sounds like it would be close to the main power cord. On the ones I've worked on one side goes to the transformer and the other goes to the switch. Although before that they go to the unswitched outlets on the back. Plug a light or fan into the back and see if you have power to those unswitched outlets. If you do, try the switched outlets. Plug the small lamp into the switched outlet and turn it on. If your light comes on then you know the power switch is working. Come back with results and we'll see if we can figure this out.

Regards,

Ron.

[Ldg]

Looking at the schematic, there's a thermal fuse in series with mains transformer primary, which might have died of boredom ? Otherwise, the red/green indicator power lamp is powered indirectly from one of the derived secondary rails, so a fair bit has to be up for that come on.

My bet's on the thermal fuse, or one of the secondary fuses.

[vineyridge]

Here is an update from yesterday's talk to the shop. I wimped out and did not pick up the amp after I asked them a few questions and learned that if I took the amp off their property, they would not apply the S75 diagnostic fee to the repair cost, even if I brought it back immediately. In fact, they would charge another $75 diagnostic fee.

Here is the gist of the conversation, which I hope I am remembering correctly:

Me: This amp does not have MOSFETs.
Technician: Yes, it does. The amp has an NPN JFET and a PNP MOSFET. One of the MOSFETs on the left output side is shorted. The amp is direct coupled and goes into protection mode when the power supply is running, thus shutting down the amp. The MOSFET kit repair would replace all MOSFETs and either the capacitors or resistors (can't remember which).
Me: Could I use the pre-amp and phono stage without using the power amp section, since the two can be separated in operation? That way, all I'd need to do is add a power amp and could take advantage of the built in phono stage.
Tech: No, because of the direct coupling feature

Because the amp goes into protection mode, they can't test the pre-amp and phono parts.

Then, yesterday evening after I got home there was an email from NAD with a list of service centers. In the email, NAD verified that this amp does not have MOSFETs.

Comments?

[Dr Pan K]

lmao. what a bunch of crooks

go to the shop with a couple of friends of yours, take the amp, dont pay a nickel and either
1) go to someone decent to take a look at it or
2) buy yself a new nad model since u like em that much