Re: LF13331 Symptoms

On Tue, 14 Oct 1997 12:53:27 -0500 (CDT), <jwelser@ccwf.cc.utexas.edu>
wrote:

>
>On Tue, 14 Oct 1997, Zonn wrote:
>
>> It could be the LF13331 but it sounds unlikely. Weird because it really
>> sounds like an output transistor. Did you do a doide check on all the
>> pre-driver transistors? Making sure they all had decent Base-Emitter
>> and Base-Collector readings and no shorts?
>
> Yeah, that's what I meant by "those three transistors" -- the 3
>transistors in the -Y deflection section. I checked them (they checked
>OK) but replaced them all anyways after I got frustrated.
>
>> Another thing you might try is to make sure the power resistors are all
>> reading the proper value. Cinematronics does have short circuit
>> protection built in, if one of these resistor values changed to a higher
>> value (or opened up), the output would go into short circuit protection
>> mode and cut off your picture.
>
> Ahhhhh, this makes a lot of sense.
>
> But, just out of curiousity, what are the typical symptoms of a
>bad LF13331?

Mostly no picture at all (dead, circuit breaker blows), but I did have
one that caused the vectors to go all haywire. Chances are if all you
vectors line up correctly it's not the LF13331, but no guarantees. I
suppose it could have a problem where only two switches of the four have
gone bad and don't conduct in one direction, but I seems unlikely.

-Zonn
Received on Tue Oct 14 11:03:46 1997