Re: Flyback Troubleshooting help

Jess Askey wrote:
> 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.

Lets not take the flyback apart just yet...

As Roger points out the image appears more or less correct for your
situation. A normal HV transformer/flyback receives a very short pulse
for a rather short duty cycle. Your duty cycle is 50% and this covers up
the ringing. What is the output like on pins 7 & 9?

I'll pull out some flybacks and see what I get for similar setups in the
next day or three.

John :-#)#
>
> 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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