Use for an odd transformer

[XgamerGt03]

So on my last project I ordered a transformer from Edcor. Said transformer was supposed to be 330-0-330 at 250mA... well instead what I got was 330-0-660.

So I now have this transformer laying around, I don't see a reason to trash it since it does in fact work. Anyone have any ideas what I could do with this. I know I could use it in a few interesting ways, if I wanted an amp that had the screen grids of tubes at exactly half the plate this would work extremely well.

It also has a 6.3VAC (5A) and 5VAC (3A)

Any suggestions guys? If I can't come up with anything interesting to build I could always use it for something like a tube burn in fixture, but this seems like I could make a manufacturing mistake into an interesting project.

[martin manning]

Are you sure? Do you get 990VAC across the outer secondaries? I don't think that much wire would fit on the bobbin.

[XgamerGt03]

It is in fact a 660-0-330. When I use my fluke meter at work with the appropriate leads I get 990 Vac. I also measured from the center tap and do in fact get 660 and 330.

[martin manning]

Wow. You can't send it back?

[XgamerGt03]

Oh they already replaced the transformer, I guess I neglected to mention that. They told me that I could just throw the transformer out or do whatever I wanted to with it.

It seems a shame to just toss it since it isn't a "normal" transformer.

[rhinson]

just use the 0-330 side with bridge rect. 462vdc unloaded---the wire in the wind is still rated for 250ma (probably 28ga) so you could use a couple of el34's or 6l6's. probably get about 410-420 on the plates under load. so you could use it for whatever you want----just use the 0-330 half of the winding. rh

[Cliff Schecht]

It is in fact a 660-0-330. When I use my fluke meter at work with the appropriate leads I get 990 Vac. I also measured from the center tap and do in fact get 660 and 330.

Err.. Be careful here. 990V AC is an RMS value which is nearly 1400V peak to peak. Most Fluke meters are only rated up to 1000V p-p max. Last time I tested a transformer with this high of voltage on a Fluke meter I blew up the meter bad. I'm talking took out a chunk of PCB and smelling up an entire lab bad. Luckily it wasn't my meter! Be careful about measuring large AC voltages on your Fluke..

[Cliff Schecht]

Oh and as far as the transformer goes, you could do some sort of switch to choose between the two secondaries going into a bridge rectifier. I'm thinking a SE amp that can switch between optimal EL34 voltages (~450V) and optimal Eimac ceramic power tube voltages (at least 900V) .

But seriously, that 330V secondary through a bridge rectifier is good for maybe 450V @150mA fully loaded which would be good for a pair of EL34's or 6L6's. The 150mA number comes from the bridge rectifier which derates the current rating by 0.62. The other option is to use a 2-diode full wave rectifier which would give you ~700V DC (good for a SE KT-120 build). By no means a useless transformer, heck I'll buy it from you if you still don't want it.

[XgamerGt03]

The meter I have is 1000VAC RMS.

I'be been thinking about trying out the 100W EL34 pair stage described in a Mullard datasheet. I could always toss some type of voltage adjustment on it and use it for a test power supply though.

I just think a mistake as interesting as this should be used for something equally interesting.