I have a rack full of blown transformers from those amps. The usual short I’ve
seen several times is one 120v primary winding shorts out. It’s been a while
but sometimes they have an impedance short to the case. Often times it takes
out one leg of the bridge. Turn on the transformer and probe all wires to
ground on 1000v AC scale.
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On Friday, June 6, 2025, 4:56 PM, Ken Claerbout <kenk4zw@gmail.com> wrote:
I've been trying to repair a Ten Tec Titan Model 425 amp and I'm about out
of ideas. Here's where I'm at.
The Soft Start 1.5 amp fuse blows.
This model power supply has the separate rectifier and filter board,
mounted on top. The soft-start and bias circuitry are on the lower board.
With the rectifier/filter board disconnected, the fuse does not blow. I
have the gray cable connected between the PS and RF deck but not the HV
cable. Anytime I connect the rectifier/filter board the soft start fuse
blows instantly. Seems simple enough. Most likely something on that
board, bad cap, diode, the usual suspects. Nope! Everything checked OK.
But NR4M had new caps from a project he did so I "borrowed" eight of those
and replaced the caps. Still blows. Replaced diodes and resistors. Same
thing, fuse blows. Everything on the board has been replaced at
this point. I don't see any burned traces on the board, like what happens
sometimes.
I pulled the lower board and looked it over. I don't see anything wrong
with it either. I don't see any DC shorts on the transformer. I've had a
few of those go bad in the past. They take out the 20 amp line fueses and
I can measure the short. So to recap
1. The soft start fuse is blowing
2. It doesn't blow with the rectifier/filter board disconnected
3. All components have been replaced on the rectifier/filter board.
What am I missing??
73
Ken K4ZW
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