Rewire this transformer?

[donzoid]

I was over at one of my oldest friends places two days ago and we (of course) started talking about gear...next thing I know he's hauling out a red-knob Fender Champ 12 (single ended 6L6) that he tells me he got in a horse trade, and never even plugged in.

Well of course he hasn't! It's the export version, with the euro plug and only switches between 220 and 240.

Well ya know I can't leave that alone. So, I went out and snagged the schematic. Will I let the smoke out if I:
Join grey and brown (neutral)
cap off/isolate yellow (220 tap)
cap off/isolate orange (that one's easy its already done its the 100v tap for Japan)
Join blue and black (hot)

...won't that give me 120v at the primary? Or will that treacherous smoke come out?

Seems to me that its the same exact setup as the MM diagram I also attached, just different colors.

Thanks in advance to the many smarter folks who will chuckle after reading this, and probably know straight away.

[Leo_Gnardo]

Join grey and brown (neutral)
cap off/isolate yellow (220 tap)
cap off/isolate orange (that one's easy its already done its the 100v tap for Japan)
Join blue and black (hot)

...won't that give me 120v at the primary? Or will that treacherous smoke come out?

Should do just fine. If smoke comes out, pass the dutchie on the left-hand side. Of course you can bring it up slowly on a variac, or use the handy light-bulb limiter while monitoring the hi voltage supply. Either way you'll know if things are going wrong before any smoke gets emitted. Good luck!

[ampdoc1]

It doesn't appear to me that any of the connections will give you a 120VAC operating voltage.

I purchased a Groove Tubes amp on Ebay a while back that has European mains. I did a quick search for a EU to USA converter, and if memory serves it was only $10-15. Cheap and easy,.. with no chance of burning it up.

Check here: http://www.rakuten.com/prod/eforcity-un ... oCsJHw_wcB

a'doc

[martin manning]

I'm with Leo. Looks like two 120v primaries, each with a 100V tap.

[donzoid]

Thanks all. Yeah Doc I had looked at those step-up / step-down converters and they are getting awful cheap. But THAT fact makes me wonder what the heck they are putting inside them (in terms of component quality).

Martin/Leo, thanks and yes I have my handy bulb limiter ready. Anymore I never swap leads without it...

Those buggers at the factory joined and capped the blue and brown leads SO close to the chassis I'll have to pull it just to get at them for decouple and soldering...but if the rest of the amp is sound, it still has its original GT GE (or it might be Sylvania, USA made in any case) 6L6 out put tube and thats a GOOD thing because the plate volts this puts out are known to eat through even the Russian 6L6's. Kinda curious what its gonna sound like!

Thanks again!

[Stevem]

Take note that these amps are massively under built in regards to the wattage of resistors used.
They even use 1/4 watt resistors in the power supply node string and the first one always smokes when these amps are run up over 3/4s where they sound best!
Replace all the 1/4 watt resistors in the power supply and in the preamp tube plate load positions with 1/2 at least and or any resistor being pumped by more than 350 volts should get upped to a 1 watt value.
And when you get that worked out and play the amp cranked enough with a strong 6L6 the OT will go south on ya!

[donzoid]

Thanks Steve, I think???

Ya, Fender was always doing stuff on the cheap, but this CBS stuff is the epitome of it.

Gotta go pick up a couple of male 120v plugs before I try ye olde bulb limiter...

[Leo_Gnardo]

Had a look at that $4.99 "voltage adapter." I wouldn't run anything more than an electric razor on it, no matter what they say.

ampdoc, I'd seek out an autoformer to bump 120VAC up to 240 with power capability rating exceeding what your GT amp draws. Used to be easy to find 'em in local surplus shops, not so easy anymore. They're a bit expensive new. Why not ping ApexJr and see if he's got one the right size for you. As a veteran of many tours thru the 240V countries, I've seen some amps and adapters go up in smoke when people try the cheapest solution.

[donzoid]

I was looking at these, but even then....not so sure...in the end though still cheaper to swap the PT leads (if it works). Got the plug, will plumb it tomorrow!

http://www.rakuten.com/prod/simran-ac-5 ... 41803.html

[Leo_Gnardo]

I was looking at these, but even then....not so sure...in the end though still cheaper to swap the PT leads (if it works). Got the plug, will plumb it tomorrow!

http://www.rakuten.com/prod/simran-ac-5 ... 41803.html

Got one of those, a traveling band castoff. The UK outlet is smashed to bits & I haven't been able to find a replacement. Other than that it's more like what you'll need to run small 240V amps. But the best thing for your Champ 12 is to rearrange that PT primary as you planned.

[donzoid]

OK she's re-wired and brought up to the 100watt bulb (behaving as anticipated, bulb going dim...just like my mind)

and we have a "fairly high" reading at 548v on B+, and 7 volts AC on the heaters.

But, there aren't any tubes installed, and we aren't "that far" from the schematic (attached). I've put in a 1 amp fuse instead of a 1/2 amp 'cause that's what I had in the drawer. I'm going to find a 1/2 amp fuse, put that in, and hook 'er up to straight 120v but I think this is it.

Leo, looks like I won't have to pass the Dutchie, even "on the left..."

[donzoid]

Steve is right too, the power string resistors on this thang are wimmmmmmpy. If this were my amp I'd replace 'em cause I'd be running it around 8 all the time anyway!

[Leo_Gnardo]

I'm going to find a 1/2 amp fuse, put that in, and hook 'er up to straight 120v but I think this is it.

Leo, looks like I won't have to pass the Dutchie, even "on the left..."

Nice to hear "the smoke stayed in the wires." Though I reckon a half amp fuse won't cut it, probably open on startup. 1A slo blo is what I'd expect to work. Also don't run it without tubes straight off 120VAC, that 548V DC while on the light bulb limiter tells me when run right off the line, you'll be going 600+ and stress the heck out of the filter caps. The tubes' current draw off the DC supply will sag it down to expected levels. Which will still be on the high side.

Why not be a hero and change out those wimpy power supply R's now. Cheap insurance.

[Phil_S]

B+ needs to go down 10%. Tubes in sockets will likely take care of that. Hope for the best. If over 500V, be sure caps are rated for 600V.

[donzoid]

OK I will leave the 1A in there, put in the tube, and I gotta hook up a load since there's no standby switch and then I'll check volts. Looks like the caps are 350v (2 in parallel) so not going to push my luck.

And yes, those resistors have been bugging me all night...I'll take a look in the bin and see if I have them handy I might swap those also...