Re: Flyback Troubleshooting help

  My generator doesn't have a DC offset, I will have to build one. I
just have a waveform generator IC that I breadboarded up really quick...
I will see if I can get a waveform generator locally that has that feature.

On 1/17/2011 2:16 PM, Rodger Boots wrote:
> Does your generator have a knob marked "DC offset"? If so, set it for
> a -4 to +4 volt square wave. Using 0 to +8 volts isn't going to give
> you useful readings.
>
>
> On Mon, Jan 17, 2011 at 2:19 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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>

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Received on Mon Jan 17 16:21:06 2011