Re: WG 19v2000 flyback sub?

Even if the HV secondary winding was open you should still get the lower
voltages. Thus even if you get an infinite resistance on the HV lead you
should still get the lower voltages as they are, AIR separate windings.
Thus if NO output voltage at all, and the primary winding seems good, then
I would be looking at the driver circuitry...one of Bob Parker's (Dick
Smith Electronics in Australia) flyback/LOPT meters would be handy about
now (not an ad exactly, but we as well as a few other folks sell them).
Very handy to verify flybacks/HV Xformers.

John :-#)#

At 06:48 AM 12/4/00, Robert Bayes wrote:

> >If you get oscillation, but nothing out of the flyback (actually a HV
> >transformer, as a flyback needs a yoke winding for it's operation-but
> >that's another group (Rasterlist))) then I would take a close look at the
> >driver transistor first, and it's connector.
>
>Thanks, John, I have checked it to the extent my test equipment will allow
>(DVM, scope).
>
> >
> >On the other hand, I have had those HV transformers that had loose winding
> >assembly and the wires leading from the coil break at the solder terminals.
> >You might be able to re-solder them if you bend the broken one out
> >carefully, burn off the insulation, then add a tiny extension wire. I've
> >managed to fix a couple that way. Oh, and then wedge in silicon glue to
> >freeze the coil windings. Other folks might want to check this on their B&W
> >vector HV transformers to make sure theirs aren't loose and do some
> >preventative maintenance.
>
>
>
>I removed the flyback and inspected it for broken connections as you've
>indicated. All connections were sound. However, I still have a problem
>determining the continuity of the HV secondary winding. I read
>"Sci.Electronics.Repair FAQ Testing of Flyback (LOPT) Transformers" on the
>web and it was ambiguous about measuring the flyback coil continuity.
>
>If I cannot read a finite resistance (before the HV rectifier) and *any*
>identifiable terminal on the flyback itself, I have a broken flyback -
>right? Unless I'm missing something here, or took the wrong exit to the
>Magic Kingdom, the HV secondary is open. Please correct me if I'm wrong.
>
>Where the anode wire physically connects to the core there is a small amount
>of movement. Could this wire have worked itself loose? If so, what is the
>likelihood of success in removing that epoxy, RTV or whatever it is coating
>the transformer and resecuring the connection?
>
>I really appreciate your help.
>
>
>
>Robert
>
>
> >
> >John :-#)#
> >
> >At 08:33 PM 12/2/00, Robert Bayes wrote:
> >>Thanks, John, for your quick response.
> >>
> >>
> >>
> >> >Are you sure the transformer is open?
> >>
> >>As best I can tell. HV circuits are not my strong suit. I measure approx.
> >>10Mohms (depending on the humidity down here in Houston) with the HV diode
> >>*out* of circuit. Should I see this *high* a reading?
> >>
> >>
> >>A common failure on these is a bad HV
> >> >diode...
> >>
> >>I bought one of those just in case.
> >>
> >>do you get the screen voltage (400V) and the 90V output from the HV
> >> >unit?
> >>
> >>I get *no* screen voltage (~0.0V), *no* focus voltage (~0.0V) and only
>about
> >>10V (should be ~95V) for the spot killer circuitry. I am mindful of the
> >>characteristic hi-z of the circuit but it shouldn't yield *that* much of
>an
> >>error through my DVM! Please correct me if I'm wrong.
> >>
> >>The HO circuit _is_ oscillating though. The feedback must be coupling
> >>through the transformer core.
> >>
> >>If so, then the unit is almost running...likely a bad diode at that
> >> >point...there has been discussion here about sources for those
>diodes...I
> >> >use ones from old B&W TV's...
> >> >
> >>
> >>
> >>Lord knows, I hope you're right. However, so far, it seems to point to
>the
> >>flyback.
> >>
> >>What do you think, given this *new* information? Any suggestions?
> >>
> >>Sincerely,
> >>
> >>Robert
> >>
> >>--------------------------------------------------------------------------
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Received on Sun Dec 3 22:33:07 2000