Re: Flyback Troubleshooting help

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 :-#)#

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com