Re: 6101 Def Board Prob

At 08:29 PM 9/19/00 +0200, Tek wrote:
>Well, Judging from the schematics, F700 will blow when the current through
>the X
>winding of the yoke becomes too big.
>This can basically happen in three occasions:
>
>1) The yoke's horizontal windings are short-circuited, which is highly
>unlikely. Check this with your VOM (Yellow - Black, mine reads about 1
>Ohm) and make sure it does not connect to ground (ie it should 'float')

#1 is not quite right. Deflection boards are transconductance amps
(voltage in current out). The smaller the load (Ryoke), the less voltage
required to produce a given current (I=E/R). Therefore, if the yoke is
shorted it will not blow F700. The second part of #1 is correct: if the
Yoke is shorted to ground, F700 could blow. This is because the short to
ground effectively bypasses the 10W sense resistor, causing the amp to
drive more current into the output stage.

I know John has said previously that you can short the input to the
deflection board and disconnect the yoke for testing, but the amp will be
running open loop, which is not a good idea... For most cases it still
will work. The correct "no load" for a transconductance amp is a
short. However, using a short for debugging a deflection board is an
advanced technique, not for the novice technician.

-Scott

>2) The output transistor Q705 or Q706 is shot. Again, an easy check with your
>multimeter, check for continuity across the CE leads.
>
>3) Q705 or Q706 is put fully open by the preamplifier. Most easy would be to
>check the transistors first there, like Q703 and Q704.
>
>The vector chatter is probably form the other winding (Y) whih can be without
>problems. The spot killer gives you the idea the AVG is generating something,
>but to be sure check this with a o'scope (if you have one).
>
>Regards,
>
>Mendel
>
>BTW, I've tried to mail you several times this week, but I did not get any
>replies. Maybe somethings wrong with your computer?
>
>Cya !
>
>chumblespuzz wrote:
> >
> > Hi All,
> >
> > I'm working on a 6101. Zannen kit installed. Def board blows F700.
> Before it
> > blows there is only very light HV chatter. Spot killer is not on. Tested in
> > a known working monitor.
> >
> > I've looked in the FAQs, etc, but there is nothing referring to F700.
> >
> > How would you suggest I troubleshoot?
> >
> > Thanks!
> > -roy-
> >

--
Scott Swazey        QUALCOMM, CDMA Technology     Work: (858) 651-8745
mailto:sswazey@qualcomm.com AA-302E               Pager:(619) 683-5210
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.