I would try bringing it up slowly to see if it is a hard short or is a hv
breakdown at some value.
On Fri, Jun 6, 2025, 7:29 PM Steve, NR4M <steve@nr4m.com> wrote:
> Ken,
> I’ve got a homebrew HiPot tester, if you think it could help.
> Steve
>
> Sent from my iPhone
>
> > On Jun 6, 2025, at 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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>
>
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