Re: Flyback Troubleshooting help

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> 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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Received on Mon Jan 17 15:26:59 2011