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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 9:58 pm
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aclempoppi wrote:
Yeah Bill, I do have a 100VA isolation trans. But all that seems too much, except on the bench. If you have any recommendation for a more condensed unit, I'd appreciate it. Art


No, I really don't. I was operating on the memory of one of my power classes is college (mid-70s) on the potential dangers of variacs and was just searching for more info to back up what I vaguely remembered. :lol:

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 10:12 pm
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Bluesky, maybe you are thinking about the "EVH Variac trick." Where he ran Marhsalls at like 95VAC to get them to OD early in the volume range. And really saturate the irons. And eventually blow them up. :oops:

BTW... I use at least 2 KVA Topaz ultra-isolation units on my LCD TV's and computers (main computer has a 5KVA on it). Just to keep the dang digital noise OUT of the AC line. I recommend no lower than 2.5 KVA for tube amp use. These units are also called "boat anchors" (see link--- note weight). Used to be able to get mil spec surplus ones for under $250...

http://www.surplussales.com/Transformer ... ers-2.html


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 10:18 pm
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BMW2002Ti wrote:
Bluesky, maybe you are thinking about the "EVH Variac trick." Where he ran Marhsalls at like 95VAC to get them to OD early in the volume range. And really saturate the irons. And eventually blow them up. :oops:

BTW... I use at least 2 KVA Topaz ultra-isolation units on my LCD TV's and computers (main computer has a 5KVA on it). Just to keep the dang digital noise OUT of the AC line. I recommend no lower than 2.5 KVA for tube amp use. These units are also called "boat anchors" (see link--- note weight). Used to be able to get mil spec surplus ones for under $250...

http://www.surplussales.com/Transformer ... ers-2.html


Fortunately, I don't have any need for anything like that. All the noise in my home studio comes from either aliens or the National Reconnaissance Office which is about 2 miles from my home. Long story. :lol:

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 10:27 pm
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Bluesky, by all means you MUST study this landmark white paper! Many "myths" dispelled.

http://berkeley.intel-research.net/arahimi/helmet/


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 10:38 pm
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I was thinking of just getting one of these new, cheap, Chinese jobs with modern wiring (polarized three-prong cords) and using it with the ground fault interrupt protector.

http://www.ebay.com/itm/Metered-Variac- ... 2186wt_754

Any vintage amp I use will have a power transformer (isolation trans.) and a properly wired three-prong cord.

The two vintage amps that I am restoring are only 5 watts. There is the aforementioned Champ 600 and a (mid-60s?) Valco model 62-9032. The Valco has an 8 inch Jensen speaker and looks suspiciously like a Fender Champ 5F1 circuit ('59 Champ).


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 11:07 pm
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BMW2002Ti wrote:
Bluesky, by all means you MUST study this landmark white paper! Many "myths" dispelled.

http://berkeley.intel-research.net/arahimi/helmet/


Already tried that. The signal is too strong. :shock:

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 11:09 pm
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jaurr wrote:
I was thinking of just getting one of these new, cheap, Chinese jobs with modern wiring (polarized three-prong cords) and using it with the ground fault interrupt protector.

http://www.ebay.com/itm/Metered-Variac- ... 2186wt_754

Any vintage amp I use will have a power transformer (isolation trans.) and a properly wired three-prong cord.

The two vintage amps that I am restoring are only 5 watts. There is the aforementioned Champ 600 and a (mid-60s?) Valco model 62-9032. The Valco has an 8 inch Jensen speaker and looks suspiciously like a Fender Champ 5F1 circuit ('59 Champ).


I don't trust anything from China that has the potential to kill me. :lol:

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 11:16 pm
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Just set up the Powerstat and the Hammond iso-trans, at 110vac. Ran the '55 Valco(with and without the reverb unit) and it loved the conditon, quieter but still in character. Got to find some kind of regulator! Art

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Tue Feb 21, 2012 11:50 pm
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Art & Bluesky are 100% correct. I've read several posts on hi-fi boards where Chinese made Variacs have shorted or failed and toasted caps, being ramped up. If you want a Variac, pay a little more and get a US made Superior Powerstat or some such unit. As long as the bearings are ok (not a lot of play in the shaft), you should never need to buy another, again.


http://www.ebay.com/sch/i.html?_nkw=+powerstat+variac


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 12:15 am
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Beemer, do you think those variacs can run the supply for hours at a time? My old guy, I just wouldn't want to trust for 3 hours,at a crack. But it's also way too big( it's a 110-240 unit). What do you think ? A 3-4 amp unit should be OK ? Art

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 12:51 am
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Art, I'd always shoot for a good 2-3 RMS amps above the rated fuse of your amp for the Variac. Five amp unit, at least. The wiring will be big enough gauge with adequate heat-resistant coating to protect the Variac from transient current spikes.

You may need to hide the thing from prying eyes and fingers. BTW... if you are going to use the unit with the amp on, all the time, I'd remove the dial. Can't tell you how many stories I've heard of Variacs getting turned down turning a gig, resulting in damaged PT's.

Really, high voltage on the outlet is not as dangerous as too low. Up to a point (say 10-15% variance). Just re-bias the output tubes. The gain/input/phase inverter stages are somewhat self-leveling, Class "A" single-ended. To protect against in-rush, during first turn-ons in the morning (cold amp syndrome), an inrush limiter works pretty well (like the CL-60) to prevent damage to tubes--- prior to warm-up.

http://www.ge-mcs.com/download/temperature/920_325a.pdf

To calculate which type/size:

http://www.ametherm.com/inrush-current/ ... miter.html


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 12:54 am
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This appears to be the Variac brand with a built-in isolation transfomer for $150. Does anyone know if these are still made in the USA? The description is written in poor English (not a good sign).

"Note that most device have surge (when first turn on) much higher than operating amp rating." :?

http://www.amazon.com/Variac-Variable-T ... 481&sr=1-1


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 1:13 am
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"Variac" is no longer Staco brand specific. The unit linked is a Chinese one. They usually have the analog meter on them.

Old, used and NOS Staco, Powerstat, General Radio, Superior Electric are all US made. A good used one will outlast most cheapie, new made ones. My Powerstat is a USN mil spec issue. With "Groton, CT" ID numbers--- 1950's era submarine testing facility stock. Still works fine.

There are ppl that repair Variacs. Brushes being the big issue on very old units. As well as the shaft bearings. You may want to talk to ppl in your area about this, before buying a used one.

http://www.nmr.mgh.harvard.edu/~reese/VariacPage/

http://picclick.com/Business-Industrial ... s/Variacs/

http://www.mindspring.com/~atlantatubeamp/id23.html


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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 7:33 pm
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Don't mean to drag this out too long, but I have a question. Instead of spending $300 on a variac, what about replacing the PT with a new one? In my case, I was just trying to keep the 1954 Transco out of respect for the builders. But actually, it has a good buzz. You can feel it, if your hand is on the trans. Which trans would you guys suggest, for (2)6SN7, 6V6, and the 5Y3 ? Art

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Post subject: Re: 1952 Fender Champion 600 -- Need Advice
Posted: Wed Feb 22, 2012 9:02 pm
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Art, If you aren't fixing amps on a regular basis, you prolly don't need a Variac. The old "light-bulb" trick works well to ramp-up caps and check for shorts on first fire-up or old units that have been sitting for awhile.

http://www.repairfaq.org/samnew/tvfaq/tvtslbt.htm

As for a PT, if the amp is a 6V6GT push-pull, Class AB1 with a bias power supply... go for a Hammond 290-series replacement for the PR or DR. You will have plenty of overhead for power surges in the line. A 300-series Hammond for foreign power sources.

http://www.hammondmfg.com/guitarLinePWR.htm


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