Bare Knuckle Pickups Forum
Forum Ringside => Tech => Topic started by: JJretroTONEGOD on March 19, 2013, 12:48:55 AM
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I have been modding a Fender Champion 600 and decided to get a Hammond Transformer but I noticed a couple of things,
it has an extra 3 wires as well as a filament red/yellow wire,
the problem is as follows:
I connect everything where I expected it to be, double and triple checking everything, turn on the power and the HT fuse blows immediately so I immediately turned the amp off...
The new transformer is a Hammond 290AEX model, any help would be appreciated.
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The extra wires are HT centre tap (red/yellow), and 5V filament supply for a valve rectifier (yellow).
The Champion 600 employs a bridge rectifier, whereas the Hammond transformer is designed for full wave rectification.
The HT secondary is 650 V with a centre tap (red/yellow wire). If you connect the red wires to the bridge rectifier this will give over 900 VDC on the HT supply.
Even if you rewired your amp to use this transformer correctly, then the HT will still be over 450 VDC which is too high for the 450 V filter caps in your amp.
In short, it's the wrong transformer for the amp.
Hopefully the fuse has done it's job and you haven't damaged any of the circuitry in the amp.
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Why were you swapping out the mains transformer in the first place ???? :?
The 260C (250-0-250) would work well IF you changed your rectifier section accordingly to a FW type to give you around 350v (in line with what the schematic shows; 366v). Mind, after losses that 260C will be closer to 325v on the plates; better for 6V6s imo - I like 300v for SE 6V6s (you'd use a 225-0-225 PT for that like the 260E). Both of these PTs are centre tapped and are therefore NOT drop-in replacements, however the changes needed are very small.
Like Frank said, you have the wrong PT for the job - put it aside for another project one rainy day.
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thanks guys, I had a bad feeling it was the wrong one :shock:, luckily nothing has been damaged so the fuse did it's job. :PI've just ordered a couple of new fuses so I can restore it back to how it was before..
I also had problems getting it to fit properly, anyway I've put the old transformer back in and will leave it alone lol
it's really useful being part of this forum, your knowledge is a great help.