Power (voltage) question

[mullyman]

I have a Mesa Boogie Single Rectifier 50w combo. When Mesa sends amps to Japan they get an overhaul once they arrive so they conform to Japan's 110v electricity system. My amp didn't get that overhaul so it's set for USA 120v. When I bought the amp it came with a step up transformer. This was easily 6 or 7 years ago. just recently I had some problems with my amp and had to send it off for repair. I don't know what the exact problem was but it was a condenser. Where? Something to do with power is all I could figure out from the conversation. My Japanese is pretty good but when it gets down to specialized topics like that, forget it.

Anyway, my question is this. Do I really need to use that step up transformer? The guy at the shop said I didn't really need it. It would be a little weaker without but  not so much that I'd notice. I had all new tubes put in too (power and pre-amp). So, can I do away with the transformer?
MULLY

 

[mayfly]

Yea - don't sweat it.  Play on transformerless.

Oh the condenser is a power supply cap.  I'm guessing the original shorted out which would cause your fuse to repeatedly blow.

 

[-CB-]

There are problems.

USA power is 60cycle, 117v nominal, which runs plus or minus 10 percent, giving you a 105-128 volt window.  Forget the crap that you read/see/hear from folks saying we used to be 110v and now we're 120v or whatever.  Its always been 117v as the center voltage, right from the get-go.  Sixty cycles too.

Japan runs 100 volts, not 110 volts.  Its 100, plus or minus 10 percent.  In some really bad places, you might see 90v in Japan.  Here's the BIG rub though.  Part of Japan is 60 cycle, and part is 50 cycle.

This is a double big ouch for tube circuits.  Running a 120 amp on 100 is bad.  Very bad.  It will make the transformers go hot, and also cause issues with greatly reduced tube life, due to cathode stripping caused by heaters not up to temperature.

If you run a 60cycle amp on 50 cycles it will distort more, because at the lower frequency, the transformers are not as efficient.  The low end will flab out, and the total power output will be lower.

A 50 cycle rated circuit can run on 60 cycles (in the tube amp world at least).

So.. what to do.

What I would do - is get a 10 amp Variac.  Now you can use whatever you like.  Most Variacs go to 140v for 120v input.  Or, they go down to 10v or so for 120 in.  You can bump your 100 volts to 118 or so for a USA amp in Japan.  Later, you can use a Japan amp in the USA if you want, by bumping our 120 down to 100.  Easy peasy.

You'll still face the 50cycle wall... but... if the voltage is correct, it should cause minimal problems as long as you dont have things dimed.  If dimed, you're going to see heat buildup, and perhaps transformer failure - but that would be a rare thing.  Mostly its gonna effect the tone, the low end, and the distortion.

Hope that helps!~

 

[mullyman]

Yea - don't sweat it.  Play on transformerless.

Oh the condenser is a power supply cap.  I'm guessing the original shorted out which would cause your fuse to repeatedly blow.

That is exactly what was happening, I kept blowing fuses. Put a new one and "POP" out it went.
MULLY

 

[mullyman]

There are problems.

USA power is 60cycle, 117v nominal, which runs plus or minus 10 percent, giving you a 105-128 volt window.  Forget the crap that you read/see/hear from folks saying we used to be 110v and now we're 120v or whatever.  Its always been 117v as the center voltage, right from the get-go.  Sixty cycles too.

Japan runs 100 volts, not 110 volts.  Its 100, plus or minus 10 percent.  In some really bad places, you might see 90v in Japan.  Here's the BIG rub though.  Part of Japan is 60 cycle, and part is 50 cycle.

This is a double big ouch for tube circuits.  Running a 120 amp on 100 is bad.  Very bad.  It will make the transformers go hot, and also cause issues with greatly reduced tube life, due to cathode stripping caused by heaters not up to temperature.

If you run a 60cycle amp on 50 cycles it will distort more, because at the lower frequency, the transformers are not as efficient.  The low end will flab out, and the total power output will be lower.

A 50 cycle rated circuit can run on 60 cycles (in the tube amp world at least).

So.. what to do.

What I would do - is get a 10 amp Variac.  Now you can use whatever you like.  Most Variacs go to 140v for 120v input.   Or, they go down to 10v or so for 120 in.  You can bump your 100 volts to 118 or so for a USA amp in Japan.  Later, you can use a Japan amp in the USA if you want, by bumping our 120 down to 100.  Easy peasy.

You'll still face the 50cycle wall... but... if the voltage is correct, it should cause minimal problems as long as you dont have things dimed.  If dimed, you're going to see heat buildup, and perhaps transformer failure - but that would be a rare thing.  Mostly its gonna effect the tone, the low end, and the distortion.

Hope that helps!~

Could you point me to a page with the variacs on it? I could do a search, I did actually, but there were so many variations that I had no idea what I was looking at. If you could point me to a specific model that would be even better.
MULLY

 

[-CB-]

http://www.amazon.com/Mastech-VARIABLE-TRANSFORMER-VARIAC-5000VA/dp/B000E0G7O4/ref=sr_1_1?ie=UTF8&s=hi&qid=1277094233&sr=1-1

That will do - big enough to run a pair of 100w amps if need be!~ 

You can get 'em used too.

bid on this - built like a frikkin tank - I got one!  Expect to pay about $65-$75 for it... built to 50's military standards, beyond well made.
http://cgi.ebay.com/General-Radio-Variac-Autotransformer-W10MT-Load-0-140V-/130401432029?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item1e5c87f1dd

The General Radio ones are all pre-wired with a outlet on the top... just plug in and go.

 

[mullyman]

Thanks for those links. I'll look into it.
MULLY

 

[Patrick from Davis]

I had to get a variac for work recently.  There are a bunch of Staco ones on eBay for quite a bit less than the full price.  I have had much better luck with the Staco ones than the knockoffs.
Patrick

 

[Cagey]

I have a Mesa Boogie Single Rectifier 50w combo. When Mesa sends amps to Japan they get an overhaul once they arrive so they conform to Japan's 110v electricity system. My amp didn't get that overhaul so it's set for USA 120v. When I bought the amp it came with a step up transformer. This was easily 6 or 7 years ago. just recently I had some problems with my amp and had to send it off for repair. I don't know what the exact problem was but it was a condenser. Where? Something to do with power is all I could figure out from the conversation. My Japanese is pretty good but when it gets down to specialized topics like that, forget it.

Anyway, my question is this. Do I really need to use that step up transformer? The guy at the shop said I didn't really need it. It would be a little weaker without but  not so much that I'd notice. I had all new tubes put in too (power and pre-amp). So, can I do away with the transformer?
MULLY

I don't think the lower voltage/frequency would have that much affect on the amp, other than a slightly reduced output and a slightly elevated temperature. If those things concern you, then use the step-up transformer you have, although that's not going to fix the line frequency mismatch so you'll still have mild thermal issues if you play the thing at full-tilt boogie.

If you put a Variac on it, you have the same situation. You'll get the voltage up to where it should be, but it's not going to fix the line frequency mismatch, so you'll still have mild thermal issues if you play thing at full-tilt boogie. For extra fun, though, it'll be possible to crank to voltage much too high, and I guarantee you that'll affect your amp. Internal DC voltages will rise to where they shouldn't be and you'll be burning up tubes (filament voltage too high) and blowing capacitors out (breakover voltages exceeded). Setting the variac too high will be as easy as dragging a cord across the dial and not noticing, or kids playing with it, pets stepping on it, vacuum cleaners hitting it, curious guests, or whatever else fate decides to throw at you.

Variacs are designed for lab use, where technicians and/or engineers keep a close eye on things. They're usually used for testing purposes, to see how circuits react to over/under voltage situations. They're not musical equipment accessories by any stretch of the imagination. The possibility for disaster is huge.

 

[mullyman]

Well, I won't be cranking it to full volume, that's for sure. It's too damn loud for that. If I use it in a live situation it'll be mic'd. I think I'll be ok without anything. I have the step up transformer already. We'll see how it goes without it for a little while. I'm thinking of selling it anyway. I want to get the new Mesa Boogie TA-15.
MULLY

 

[Cagey]

I'm sure it'll be fine. Larger electrolytic power supply filter capacitors fail from time to time; they're somewhat consumable parts. But, it's much more likely to happen from age or over-voltage than under-voltage, so you probably just had a fluke. As for the cathode stripping CB mentioned, it's not an issue in audio amps. The voltage is far too low, as is the frequency. You're more likely to see that sort of thing happen in magnetrons for radar sets, where things operate in the kilovolt range at gigahertz frequencies.

 

[mullyman]

The more I'm learning about this stuff the more I'm assured you amp guys are going to slap your forehead and call me an oaf after I tell you this.

I've had the amp for probably 7 years or so and never changed the tubes. The amp didn't get a whole lot of use but still, the tubes hadn't been changed in the time I owned it and God only knows how long before that. The guy I talked to at Mesa said something like a tube flash could blow the condenser. Whatever the hell that means. Anyway, I had the amp fixed last week and had all new tubes put in too. Power and pre-amp. I think it's 2 6L6's and 5 12ax7's. The grand total on the repair and tubes came to a whopping 400 bucks. That was 400 I hadn't planned on either, the same month I get a 400 dollar bill for my yearly car tax. So yeah, I got to shell out 800 bucks this month. Thank God I get paid tomorrow. hehe!!!
MULLY

 

[Cagey]

There's nothing "oafish" about that. I'm sure you've heard the old saw: If it ain't broke, don't fix it!

There are hundreds of myths about tubes on the various musician forums around the 'net, and woefully few facts. What's funny is the facts rarely get much traction, while the myths perpetuate and propogate like mosquitos in a swamp.

One of the facts is that tubes vary in their performance pretty dramatically, even within the same manufacturing run. You can replace a new tube with an old one and get different (better?) performance, and vice-versa. Does that mean one of them is bad? No. They're just different. You can get the same sort of behavioral changes by exchanging new tubes with new tubes or old tubes with old tubes. This is most often exhibited by people changing [insert brand name here] tubes for [insert brand name here] tubes. This gives rise to all sorts of "facts" about how "JJ" tubes are much, much better than "Ruby" tubes, which are better than old "RCA" tubes, but not as good as new "Sovtek" tubes. It's all a bunch of horse feathers.

Usually, it's not time that takes out tubes as much as it is environment, and guitar/bass amplifiers present some of the worst environments. The tubes are often run at the hairy edge of their performance specification while in a violently vibrating mount, and are frequently moved around and bumped into things or dropped/set down heavily or transported in cars/trucks/busses/planes/trains/etc. whose suspension transmits a lot of impact. All that physical abuse causes the internal elements to get loose and change spacing, or become resonant at certain frequencies.

If your amp sees a fairly easy life at lower volumes with little transport, it's quite likely an electrolytic capacitor will dry up and fail before a tube will. Often when old amps are found in basements and attics, that's the worry when you power them up, not that the tubes won't work.

 

[-CB-]

Some, but not all tubes, are designed to take a fair amount of physical shock, were used in car radios, aircraft radios, etc...

*****Variacs are designed for lab use, where technicians and/or engineers keep a close eye on things. They're usually used for testing purposes, to see how circuits react to over/under voltage situations. They're not musical equipment accessories by any stretch of the imagination. The possibility for disaster is huge.****

Nothing wrong with using a variac outside the lab.  Its done on stage all the time.  But please do monitor things.

The real disaster with variac use is the heater voltage.  Too low... you trash the cathodes, too high you burn out the heater.  Thats the biggie.