Re: WG 19v2000 flyback sub?

I had some luck testing the infamous dead red Amplifone HV transformers
by using an audio frequency generator connected to the B+ winding,
and looking at the other windings output on a CRO.
I don't have my notes here but I think I put in 10KHz, 10Vp-p sine wave
from an ordinary signal generator,
and looked at the outputs, if you want to know more send me a message,
I'll dig out my notes with the voltages and waveforms I saw.
The red transformer has an integral diode so I couldn't do resistance
measurements on the output. (note this is an Amplifone one)
Kind of a manual version of the LOPT meter I guess

Marc

> 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 Mon Dec 4 00:47:35 2000