On 19 Jul 00, at 13:53, Vasile Surducan wrote:

> Hi all again,  with [EE] and :
> I desperately need schematic for high voltage stage of Compaq
> V70, 17 inch colour monitor.
> Here it's a a hybrid circuit named IC501. I suppose this circuit have
> a malfunction... If there is here a technician who works at Compaq
> please mail me !
   Compaq V70 has a strange HV circuit: instead of a normal
connection : primary HV coil between transistor's collector and +B
( 195 V ), emitter to ground, like in most usual HV stage, the
transformer coil is "charged"( with LI 2 ) from 195V through a 1 ohm
resistor and a capacitor, to ground with a small MOS-FET
transistors ( drive by IC501) and "discharged" through the capacitor
and collector-emitter of the HV transistor who is floated from
ground !
  If accidentally both transistors are on ( like now ) the collector-
emitter jonctions of HV transistor is blowing out and becomes a
wire!
  Nice problem, isn't ?

> Vasile
> *********************************************
> Surducan Vasile
> mail: vasile@l30.itim-cj.ro
> URL: http://www.geocities.com/vsurducan
> *********************************************
>
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****************************************
Surducan Vasile
email:vasile@l30.itim-cj.ro
URL:http://www.geocities.com/vsurducan
****************************************

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