[TechAssist] Re: RCA 32GT720 chassis CTC203CF3 no power blows Q14401
- From: Mike Barnett <passthecash@xxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 21 Nov 2001 09:48:58 -0800 (PST)
Dennis, this chassic NEVER ran in standby mode. alway has had same problem.
As soon as you plug int the set to AC it blows both, the fuse and q14101. I
have replaced 14102 and 14103 at the same time of replacing q14101 and get
the same result. However, i have one each of these parts left and after
changing the fly I ONLY CHANGED Q14101.
I'll try one more time.
Thanks,
MIke
On Tue, 20 Nov 2001 21:38:11 -0800, techassist@xxxxxxxxxxxxx wrote:
Mike:
Did this chassis run in standby mode for any time before it was turned on?
If
Q14101 (regulator) is or was shorted you must replace Q14102[pn# 147665] &
Q14103 [ pn# 232218) on the gate circuit of Q14101, no mater if they check
good
using static mode testing.
Q14102 and Q14103 form the basic latch circuit. Both are switching
transistors
that will saturate when tripped on. In this case an NPN and PNP are used
to
force the desired results on the gate of Q14101. The latch is controlled
by
placing or removing voltages on either base while sufficient voltage is
present
on Q14103(E) to set the latch. If these devices are not balanced one
transistor
will stay latched and never start up the chassis or the other will latch
and
destroy the Q14101 instantly.
Dennis Viereck
Mike Barnett wrote:
> Today i changed the fly with a brand new one, changed the reg and put a
new
> hot in too, checked both the primary ps and hot curcuit carefuly. could
not
> find anything bad. So i put power too it and emediatly when plugged in
main
> fuse blows also causing q14101 to short also. any ore sugestions on the
set
> would be great.
>
> Thanks,
> Mike
>
> On Fri, 16 Nov 2001 19:08:05 -0500, techassist@xxxxxxxxxxxxx wrote:
>
>
> Is the q that keeps blowing the hot or the b+ regulator? I don't have
that
> print. What you must do is cut the circuit in half......is it the h.o.
> circuit or the power supply. Get the horizontal out of the picture by
> disconnecting the fly and put a load ( l.bulb)on the 135 volt rail.
You
> obviously don't have a dc short on the transistor (you don't do you?)
> which
> leads me to believe it's the fly. Get it out of there and see. I have
the
> Sencore HA2500 Horizontal Analyzer which makes quick work of this kind
of
> stuff.
>
>
>
>
> ----- Original Message -----
> From: "Mike Barnett" <passthecash@xxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, November 16, 2001 10:53 AM
> Subject: [TechAssist] Re: RCA 32GT720 chassis CTC203CF3 no power blows
> Q14401
>
>
> >
> > Thanks for the suggustion, i've heard of this test however i have
never
> > tried it. Can you explain the result of this test in a good and bad
> sinario.
> > The problem is that in order to keep testing other things on this
board
> i
> > have to keep replacing q14401 and the fuse. as soon as i plug the
set in
> the
> > main and q14401 blows. with a new q14401 and fuse in place, and
> implementing
> > your suggestion, if the fly is bad i'm thinking than q14401 should
be
> stable
> > and the fuse sould not blow. However if it is not bad(fly) q14401
should
> > blow and the bulb should light? Please correct me if i'm wrong.
> >
> > TIA,
> > Mike
> >
> >
> > On Thu, 15 Nov 2001 09:22:48 -0500, techassist@xxxxxxxxxxxxx wrote:
> >
> >
> > sounds like the fly. desolder hot and fly primary and put a light
bulb
> in
> > place of fly primary b+ input to ground.
> >
> >
> > ----- Original Message -----
> > From: "Mike Barnett" <passthecash@xxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Thursday, November 15, 2001 9:14 AM
> > Subject: [TechAssist] RCA 32GT720 chassis CTC203CF3 no power blows
> Q14401
> >
> >
> > >
> > > Hi guys, RCA chassis # CTC203CF3 Set blows main fuse and
Q14401. I
> > changed
> > > Q14401 and the two small transistors in curcuit(Q14402/pt#147665
and
> > Q14403
> > > pt#232218) I checked the horizonal curcuit but found nothing to
be
> bad.
> > > Changed HOT anyway and checked all diodes in both curcuits. None
are
> > bad.
> > > Cant seem to find anything shorted on the board. After carefull
> > inspection
> > i
> > > did notice that the insulator of q14401 is very thin and seemed
that
> in
> > > removal of the original device i may have comprimised the
insulator.
> i
> > put
> > a
> > > new one on and changed q14401 again and checked it carefuly.
plugged
> the
> > set
> > > in blows again both q14401 and the main fuse. Does anyone have
any
> info
> > on
> > > this chassis? Please help.
> > >
> > > TIA
> > >
> > > Mike
> > >
> > >
> > >
> > >
> > >
> > >
> > > Get It Fixed At
> > > Rochester Electronics
> > > 630 West Ridge Rd.
> > > Rochester, NY 14615
> > > 716.663.6870
> > > www.RochesterElectronicsRepair.com
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
>
>
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