[TechAssist] Re: MAG: 25X6 chassis Quick Question?
- From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sat, 19 Jan 2002 23:21:41 -0800
No need to blow up any parts. Use a 40 watt light bulb in series with the B+ to
the flyback. Connect your oscilloscope to the collector of the horizontal output
transistor. Set the scope to resolve a 600 volt PP signal at 10 micro seconds
per division. Power up the set an look for a clean undistorted pulse with a duty
cycle of 11.7 microseconds "OFF" time and a "ON" time of 51.7 microseconds.
Any extra ringing or distortion means you have a heavy load on the secondary or
an internal shorted winding.
The light bulb saves components, and buys time to measure the "Must Haves" in
that circuit. Sometimes only 2 or 3 seconds is necessary to make this
measurement. Most of the time after a short test like this and it is a flyback,
one can feel the heat generated in the flyback by the bad winding or diode
stack.
Dennis Viereck
Bill McFarland wrote:
> Hey no problem,
>
> The old "N" chassis used to do this all the time (The flyback was almost
> always bad)
>
> I was just wondering if anyone could say "Yea those crap the bed all the
> time!" It would give me a little more to go on when on Monday I use my
> "Stone-aged" BK 1077 to ring it. (Its only about 75% effective...And that
> only if the flyback is completely out of the unit)
>
> I hate blowing parts up!
>
> Funny thing is now that "I" am the one paying for the parts. I sure am a lot
> more careful about things like this. When I worked for someone else it was
> faster to just change the HOT and Reg. and see if it blows the HOT back up!
> (I was young...What can I say)
>
> Good luck, God Bless
> Bill McFarland
> DMC Electronics
> Salt Lake City, Utah
>
> ----- Original Message -----
> From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Saturday, January 19, 2002 8:37 PM
> Subject: [TechAssist] Re: MAG: 25X6 chassis Quick Question?
>
> >
> > Opps... I can't read.... Never mind. You might be right......
> > Dennis Viereck
> >
> > Dennis Viereck wrote:
> >
> > > Depending on how the STR is shorted, I would the think the set would
> still
> > > run. Assuming the AC line voltage is reduced enough to achieve 130VDC at
> the
> > > output of the regulator. This is a simple linear regulator and easily
> > > bypassed.
> > >
> > > A "Shorted" STR certainly would not point me in he direction of the
> flyback.
> > > Maybe if you had a shorted horizontal output transistor, I might feel
> > > inclined to agree with you. But certainly not on 1 shorted part and
> > > intestinal feelings......
> > >
> > > Dennis Viereck
> > >
> > > Bill McFarland wrote:
> > >
> > > > Hello all,
> > > >
> > > > I am working on a 25X6 Maggot-box.
> > > >
> > > > Shorted HOT, Bad STR30130 Regulator.
> > > >
> > > > My gut tells me the flyback is probably bad as well.
> > > >
> > > > Can anyone tell me if the Flyback is a common failure item in this
> unit?
> > > >
> > > > Good luck, God Bless
> > > > Bill McFarland
> > > > DMC Electronics
> > > > Salt Lake City, Utah
> > > >
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