NAD: Mk. IV and questions

[peterc52]

So I picked this up today, and I was very excited!

It works perfectly, but I haven't had a chance to crank it up yet, soI'm really looking forward to doing that.

I'm thinking of throwing it at a tech to have the tubes changed and to have a check up, just to be sure that's everything is working correctly.

Any help on choosing tubes? - I'm thinking about 2xEL34 and 2x6L6. And it gotta be cheap for now, I'm short. How are the JJ's?

It is importet from the US, but at some point someone changed it to 240 volt.

Pictures:

As you can see it's missing 1 slider-knob on the eq, but that shouln't be too hard to find.


The serial number is by the way 68**, any idea on how old it is?

And when do you know it's time to change the caps?

Regards Peter from Denmark.

8)

 

[Geiri]

There Peter and welcome.

I have a mk4 combo and recently retubed it with all jj's 6l6. It sounds fantastic. I haven't tried the el34 6l6 blend and really don't care for it since I love the way it sounds with 6l6.

Regarding the cap job, I'm sorry but I have no idea wether there is a time limit or not. A decent tech should be able to determine for you if your amp needs a cap job or not.

Hope this helps

Geiri from Iceland

 

[gummx97]

My experience with JJ tubes are good too. I have the hi-gain option for my Mark 4, no complaints so far. The rest of my amps also have tubes from JJ's, I am just satisfied with their product and service. Check their website and maybe send them an email, they respond promptly, and I think, honestly. I once asked if they recommend a re-tube on a brand new fender amp I bought since I've read that the stock tubes were not that good, they responded by recommending i use the tubes first and get my $$'s worth out of them before re-tubing. I appreciated that type of responses from businesses.

No idea how to tell if capacitors needs replacing, maybe if one opens up the amp and inspect the capacitors for physical damage, or even measure it's capacitance, but I'd leave those high voltages to qualified technicians.

 

[Kiwiaxe]

I replaced the caps in my Mk IVa combo recently, and it made a huge difference to the white noise/hum (from annoying to zero!)

I understand the basic rule is 10 years, but if the amp is left unused for a lengthy period of time then that dries the caps out faster.

It wasn't an expensive exercise to do, so its a worthwhile piece of maintenance. I'm about to send in my Mk IVa head in for the same treatment.