Got a new flyback from Union and installed it.
Everything seemed ok, but I noticed that the HV
regulator seemed not to be working.

The problem turned out to be a shorted 820pf
capacitor on the HV splitter voltage sensing circuit
that is mounted on on the splitter itself.

Thanks for all the tips folks
--DM--


"Dave Moore" wrote in message
...
I just fixed an early Family 1 version PTV for a
friend of mine. What a nightmare, fixed SMPS,
replaced 7 bad xstrs and numerous weak caps
in convergence power section, repaired no video,
and no sound problem ( TV from hell:-),thought
all was ok, then the dang thing just quit working.

After defeating/bypassing a number of the shutdown
circuits I got it to run for about 5 seconds. Just long
enough to notice that the HOT was getting hot.

So, I figured that the flyback was probably bad.
Out of desperation to verify this, I took a flyback
off of a 169 chassi for a 31" TV.

Ok, here's where it gets interesting. After studying
the situation a bit, I determined that the black wire
for the PTV flyback and the same black wire for
the 31" TV are not the same. On the PTV, this black
wire is the other end of the CRT anode winding,
and not the focus tap like it is on the flyback for
the 31" set.

So, I put the 31" flyback in the PTV, only I didn't
connect the black wire to the HV regulator board.

Instead I cut
the ground traces going to one of the pins on the
flyback which I had determined was the other end
of the HV anode winding for this 31" flyback and
soldered my own "black wire" to this pin and connected
it to the HV regulator board.

Well, the PTV came up and worked beautifully. All PS
voltages measured within specs and the HV measured 28K.
a little low I think but the picture looked fine. Well, I ran it
for about 8 hours and started to work on adjusting the
convergence. While I was working on the convergence, the set
went *POP* and shut off and immediately came back on.
Then about 5 minutes later it did the same. Then after that.
it never did this again for about 3 hours.

After I finished the convergence I shut her down and told my
friend that he could give it a go if he wanted to, but I didn't
really trust it. Sure enough, when he came to get it, we
turned it on, it came up and went *POP*,, for good this time.

Ok, I am about to order a new flyback from MCM for $29.
I just stumbled on a thread in the freelists group where some
techs are discussing some problems with the replacement parts
for this set. Also I found an article by JURB in the SER
Google archives about this same issue.

So, 2 questions,,, anyone have any suggestions about why
2 flybacks crapped out when everything seemed to be ok?
I realize that the 31" flyback may simply not have HV diodes in
it sufficient to handle the beam current in the PTV, but I really
have some doubts as to whether this was the reason that the
origional flyback checked out.

2'nd question,, anyone had any problems using the sub part
232191 from MCM ?

Thanks
=^^=DM