Re: Flyback Troubleshooting help

  but I don't think that is the waveform that I was supposed to be
seeing.... Im supposed to see something more like this...

http://www.djlewis.us/files/electronics/blue/ringtest.jpg

plus, given that I was putting in 8V that should have put my anode
voltage more like 1500V or at least higher than 2V. :-)

I think that one of the windings must be shorted.

Time to disect the flyback.

On 1/17/2011 1:26 PM, Rodger Boots wrote:
>
> Seems reasonable to me. HV is going to be nearly nonexistent with
> that low of primary drive.
>
> On Jan 17, 2011 2:21 PM, "Jess Askey" <jess@askey.org
> <mailto:jess@askey.org>> wrote:
> > Okay, I put the standalone LOPT onto my square wave generator
> > (unfortunately my generator can only supply 30ma) so Im not sure
> that is
> > enough.
> >
> > Here is the signal before attaching the LOPT.... 15KHz 9vP-P
> >
> >
> http://gamearchive.askey.org/Video_Games/Manufacturers/Atari/monitors/amplifone/raster/images/generator_output_15k.jpg
> >
> > Here is the primary with that signal attached... secondaries are
> exactly
> > the same waveform, yet in different ratios (and those ratios are not
> > correct)
> >
> >
> http://gamearchive.askey.org/Video_Games/Manufacturers/Atari/monitors/amplifone/raster/images/lopt_ringing_15k.jpg
> >
> > Doesn't look right.
> >
> > When I read a DC voltage on the Anode cap, I have 2.2VDC, pretty
> low. :-(
> >
> >
> >
> > On 1/17/2011 12:36 PM, John Robertson wrote:
> >> Jess Askey wrote:
> >>> From what I read, I figure that if there was a short the Q would be
> >>> lowered enough that I wouldn't get any ringing... even in circuit.
> >>> However, with that said, since my ringing is drastically *lower* than
> >>> I expect (I thought there should be a 300V oscillation on the
> >>> collector with a 36V supply), something is dragging this down.... so
> >>> I think it is simply ringing at the expense of excessive current
> >>> because the Q *is* lower.
> >>>
> >>> I will try the low voltage out of circuit ring test today and report
> >>> back... with the low amounts of current, Im guessing that I will not
> >>> get a *good* ring out of it.
> >>>
> >>> jess
> >>>
> >>>
> >>> On 1/17/2011 12:56 AM, Rodger Boots wrote:
> >>>>
> >>>> John, it's a raster monitor, not vector.
> >>>>
> >>>> So why is it ringing in the first place? Is the damper diode
> >>>> connected? Is the horizonal output transistor the correct part? Is
> >>>> the correct yoke winding connected? Is the filter capacitor on the
> >>>> power supply to the output transformer working (should be DC to the
> >>>> transformer, very little AC).
> >>>>
> >>> ---------
> >>
> >>
> >> Have you checked your input bridge yet (4x 1N4004) as well as the 12V
> >> regulator U4(78L12) (not too likely, but if shorted then Q7 is also
> >> bad) for damage from the un-isolated 120VAC power test you did? PTC1
> >> should be fine - no connection to ground there. Pg 54 of schematic PDF.
> >>
> >> I would separate the flyback from the circuit and then hook up pins 1
> >> (common) and 4 (pulsing DC) to some AC supply using a bridge rectifier
> >> to get pulsing DC running at the correct frequency (otherwise the
> >> transformer is not efficient - results will be skewed lower). Hook a
> >> scope up to pins 1 & 4 to see the picture, it should be fairly clean.
> >>
> >> Then scope pin 5 to see if you have a bit of a boost on the pulsing
> >> DC, next scope across pins 7 (probe) & 9 (common) should show AC about
> >> 15-20% of the original input voltage (120/24), pins 6 & 9 showing
> >> around 5% (filament of 6.3VAC). You can also use a HV probe (if you
> >> have one) for the HV output, again it should be the ratio of your test
> >> voltage to 120V.
> >>
> >> John :-#)#
> >>
> >
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> chris@westnet.com <mailto:chris@westnet.com>

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Received on Mon Jan 17 15:37:44 2011