New Variac for Joule Electra Amps

I have a VZN-80. It is 7 years old. Last year, the variac started to get very hot and there was a burning smell. I did not look to see if there was any glowing. I took the variac to my local tech, and it turned out the problem was a defective fuse holder. He said the one provided by Joule was under-spec'd. He put in a higher value fuse holder, and all has been well since.

Outlier,

Is your Variac one that self-adjusts to keep the voltage constant within a fairly tight tolerance? Possibly made by Monster?
http://www.amazon.com/Monster-Cable-MPPROAVS2000-Channel-Conditioner/dp/B0002ZO5W2

Or is it the type where you set it manually to raise or lower the voltage for the desired loaded output voltage of the unit?

Does you mains voltage fluctuate a lot? Or are you just trying to compensate for a too high or too low of a voltage? If the latter you could use a buck/boost transformer configured as an autotransformer to solve the voltage problem

Hi Jea48,
Thanks for the input. The variac is the latter; manually 'dialed up' to operating voltage of approximately 166 volts. It's not a branded variac; it came with the amps, and am sure is designed for the amps. It's part of how the joule amps work. Even the latest Joule amps have a variac, but they are internal, one per amp, but mine is a single, outboard one. It's not an optional piece of kit - my amps won't function without it.

The reason I need a new (or rebuilt) one is because it's no longer working properly; the core has likely failed, because it's sparking a bit when I initially dial it up, and then glowing, with a slight burning smell when operating.

Outlier,

Sounds like you slowly ramp up the variac with the amps connected, powered on, and then set the desired voltage under load. This action over time will cause wear on the brush that contacts the autotransformer winding directly proportional to the connected load of the Joule Electra amps.

First I would not try to use the variac until you have it checked out. It could be something as simple as a fuse holder as Thaluza stated in his post. Or maybe even a loose connection. Or it could be more serious like a bad brush on the dial slider arm that contacts the winding of the autotransformer. If that is the case hopefully the autotransformer winding is not damaged.

If you are the least bit mechanically inclined you could pull the cover from the variac and have a look inside.... Make sure the variac is unplugged from the mains AC power before you start.... You could then see where the problem is. Look for a burned spot that will more than likely show signs of black carbon and will have a burnt smell.

Here is a nice video I found doing a Google search.

https://www.youtube.com/watch?v=M8cJrJyR87o
.
Jim

Thanks guys for the input. I'm not so mechanically inclined, but am ambitious enough to try.

The variac used to have the original (small) fuse holder scenario, and the fuse kept failing on me, so I sent it back to Joule and they replaced it with a massive essentially external (sticking out) fuse assembly which has since been bullet proof, so I don't think it's the fuse in this case. Just to be sure, I had swapped out a new fuse just to see if there was any change in operation and the sparking, glowing and burning symptoms were still there.

I'll see if I can investigate further

I managed to open the variac and I saw that the windings were blackened generally, there was little to any 'brush' to speak of and probably most worrying, there was a vertical segment of the winding that was essentially gone (the outer metal winding was likely smoke/carbon at this point, revealing an inner winding. I guess it's hard to describe but I have the photo.

I wish I could just buy a cheap new one or have this one fixed quickly, but am guessing there's no recourse there?

I guess I'll have to bite the bullet and ship it to the after-warranty service dept.

Outlier,

It's toast! It is not worth repairing in my opinion. I would just see what a new one would cost. A new one will come with a warranty.

The variac is the latter; manually 'dialed up' to operating voltage of approximately 166 volts.
12-09-14: Outlier

166 volts? Why so high? Does the power amps have a regular US 15 amp 125V plug on the end of the cord?

You can buy variacs all day long that go up to 140V that plug into 120V mains power.

Somewhere on the variac should be a data plate showing the input voltage and the FLA, full load ampere rating of the unit. It should also list the max output voltage.

Here is one manufacture I found using google.
http://variac.com/staco_3pn10_20.htm

Scroll down the page to Portable Voltage Doublers - 120V input/0-280V output.

http://www.iseincstore.com/3pn2520b-xdamvariabletransformer120vacsinglephaseinput0-280vacoutput43acasedmodelwithcordplugreceptaclelightedswitchandfu.aspx

Note the 250 volt output receptacle.
.

Hi Jea48,
Thanks for the great info. Yes, I'd feel far comfortable buying a new one, assuming it will work with the amps.

The 166volts recommended setting is likely because the momoblock amps are approximately 160 watts per channel into 8 ohms and the variac is driving both of them (Could that be it? - The setting recommendation is quite specific in the instruction manual). A friend of mine had the VZN-80 (which is essentially the stereo version, but half the power - like one monoblock with two sets of speaker outputs in inputs) and the voltage setting for his variac was essentially half mine.

My wall outlets are regular 15-amp.

I think a key reason an aftermarket variac may not work though is that the one that came with the Joule connects between each amp twice (an output power cable from the variac to the amp, and back from the amp to the variac, for each channel). Two of those connections are hard-wired from the variac and plug into the amp, and the other two connections are regular/removable power cords (plugging into the variac via male connection and into the amps via female connection, if that makes sense). I'm not sure why that 'feedback' loop is there...and I don't think other aftermarket variacs have that setup.

If it's useful I could send photos..

Thanks again for the great help. I certainly would feel more comfortable with a new variac, but would it work with the amps (especially given what I assume is some 'feedback cabling' that is employed with the Joule amps)?

I think a key reason an aftermarket variac may not work though is that the one that came with the Joule connects between each amp twice (an output power cable from the variac to the amp, and back from the amp to the variac, for each channel). Two of those connections are hard-wired from the variac and plug into the amp, and the other two connections are regular/removable power cords (plugging into the variac via male connection and into the amps via female connection, if that makes sense). I'm not sure why that 'feedback' loop is there...and I don't think other aftermarket variacs have that setup.

That is where you call in a qualified tech.

Why does it take 10 weeks?? Joule's website sites an average turnaround time of 6 business days with the longest being 15 days.

Outlier,

For what the Joule Electra VZN-160 amps retailed for new I would buy the variac the manufacture recommends from the manufacture. From your last post there is a lot more going on than just varying the voltage to the amps. It sounds like the variac is built/mated specifically for the amps.

I would suggest when you get the new one keep a log on the hours used. Check the autotransformer winding wiper brush for wear and have it replaced long before it’s end of life.
I also hope your amps were not damaged when the variac started arcing.

Best of luck,
Jim

Outlier,

For what it's worth had the 120V branch circuit that feeds the variac been protected by an AFCI,(Arc Fault Circuit Interrupter), breaker the breaker would have tripped open when the variac started series arcing. I am just not sure if under normal operation of the variac a slight arcing of the wiper brush contacting the bared autotransformer coil as the variac was ramped up or down might cause the AFCI breaker to trip open.

You could have an electrician install an AFCI breaker in the electrical panel that feeds the branch circuit and find out when you get the new variac.

Note, depending how old the electrical panel is and manufacture of will determine if the electrical panel manufactured breaker will fit the model/style/series of your panel.

AFCI breakers have been in use since 1999. As per the 2014 NEC code all newly installed 120V 15 and 20 amp branch circuits used for lighting and receptacles in habitable areas of a residential dwelling unit shall be AFCI protected. It should be said the AHJ, (Authority Having Jurisdiction), has the final say where they must be used.

http://www.afcisafety.org/qa.html
.

Jea- Yes this a purpose-built variac on the Joule amps. Given the heat load that 16 of those 6cc3b tubes put out, there must be a $hitload of juice (that's as technical as I get) of current or voltage or whatever being dissipated by those amps to be able to put out 160 wpc so I would be very cautious about using anything other than Joule-supplied variac.

Outlier- FWIW, did you follow Jud's directions as far as slowly ramping up voltage when you powered up the amps?

Disclaimer- I owned a VZN-80 for several years. Other than that, I have no technical or engineering skills. Bit I did stay at a Holiday Inn ;-).

Hi Swampwalker, yes, I've been very careful to follow Jud's guidance on dialing up the variac - per his actual words - a smooth, constant motion taking about 5 seconds in total.

The variac is actually very rickety though - my sense is that plenty of aftermarket variacs are bigger and have more tolerance that this one. The core itself is very small compared to some I've seen. I'd love to have one per amp - that would at least half the load, which may be part of the problem with using this little thing to drive both amps.

Hi Outlier,

Have you contacted Joule Electra and asked if they will sell a new variac to you? That would be great if they would. I thought Jud Barber retired recently due to age and health concerns.

Outlier- That seems to jibe w my experience w the VZN-80...not the sturdiest construction, that's for sure! Not to denigrate the sound, but no one could Jud of going the 1/2" thick CNC-machined faceplate route ;-)

Hi Thaluza, I have explored that route (and that would definitely be my preferred route), but it was not an option. I'm working with Rich at Signature Sound in NY on a rebuild - I've been very happy with his speedy and thorough engagement so far though I understand that there are no guarantees on what may be possible but will see. It may involve retrofitting a new variac vs. fixing this existing one.

Swampwalker, yes, it's a pity that these units aren't more bullet-proof. It's hard to put a price on reliability - it's easy to take it for granted until something goes awry with one's equipment..

Outlier- Should have thought to suggest talking to Signature Sound...they have always been heavily involved w Joule (and Merlin) gear. As for build quality, it's not only electrical reliability, but also mechanical that I was concerned with. That is to say that the physical integrity/strength of the casework, I/O jacks/posts, etc, did not seem to be consistent with the sound quality. But that might also have been a function of buying on the used market with unknown # of owners andshipping cycles. Hope you can get the amps up and running soon; winter is their "peak season" ;-)

The Joule variacs are indeed custom applications. When I looked at aftermarket variacs it became apparent that nothing would work "off the shelf".

Fair warning: The Service Dept (CT) may have quoted you 10 weeks but a VZN-80 I sent in for repair took approximately 6 months. PM me for more info but you should send the unit to someone who wants to actually work on them. they are also unable to get any parts, schematics or other info from Jud anymore.

I wanted to post the fact that there was a happy conclusion to this issue. I sent the kaput variac to Richard Brkich at Signature Sound. Rich is pretty familiar with the Joule amps and uses a pair himself. He researched my variac, got a new one(higher spec/capacity) from a great source for a great price. He then did the custom work on ensure that it would work perfectly in my application. I got the variac back in a timely fashion and there was always excellent communication and attention to detail along the way.

Independent of Rich's help, I bought 16 new power tubes as it became clear that I had some runaway current on at least one tube.

I'm not back in business with a wonderful sounding pair of amps that are very stable and the variac is prefect again.

I could not have hoped to work with a better technician/expert than Rich - he was a joy to deal with and I cannot recommend him highly enough if you ever need any work done or if you are in the market for new equipment. His advice and recommendations were thorough and super helpful and he was very generous with his time.

I'm back to a lot of happy listening now (exploring my new Tidal subscription and exploring more vinyl with a new Thor phono-stage as well). Happy listening!!

Great! Good deal, Outlier.

Thanks Swampwalke.

I meant to say ..."I'm NOW back in business with a wonderful sounding pair of amps" and not 'I'm NOT back in business..." ;-)) Spelling is not my forte sometimes.

Happy to hear Rich was able to help you out. Is Joule Electra still in business? Jud hasn't been at any recent shows as far as I know.

I believe that Jud is no longer handling day-to-day activities for the business, but Simon Thatcher seems to be involved in the business and managing communications in a timely manner when I reached out to the Joule email alias.

Outlier,

Sorry to be the bearer of sad news here, but our friend, Simon Thatcher has recently passed away. Simon, a brilliant, kind and humorous lover of music and audio will be greatly missed. Besides his technical writings, Simon consulted on the development of many great audio products with companies such as Spectron, Joule Electra and Stillpoints. He was also for many years an active participant in his local audio club, the Philadelphia Area Audio Group.

R.I.P. Simon.

Spencer

Spencer,
Am sorry to hear that sad news. My thoughts are with him and his family.

Best,
John