[TechAssist] Re: RCA Projection PTK169PTA U4101 prob. (no stdby voltages)FIX?

  • From: "Damon" <DAMON101@xxxxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Thu, 2 Oct 2003 22:55:43 -0500

We just had one in that had 240 v in standby and found that CR4118 had
shorted, caused it to turn on fully to compensate.

Damon Brunger
Telrad Electronic Services
Ft Wayne, IN 46815

----- Original Message -----
From: "al m" <ampm@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, October 02, 2003 6:45 PM
Subject: [TechAssist] Re: RCA Projection PTK169PTA U4101 prob. (no stdby
voltages)FIX?


> The only time I had that much voltage in standby the 2.2mf 100V cap fixed
> it.
> Al Marquardt
> ampm@xxxxxxx
> Al Marquardt Electronic Repair
> 206 W Main
> Girardville Pa. 17935
> ----- Original Message -----
> From: "Larry Eastman" <videotech@xxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, October 02, 2003 6:50 PM
> Subject: [TechAssist] Re: RCA Projection PTK169PTA U4101 prob. (no stdby
> voltages)FIX?
>
>
> > Hi guys, I found it, thanks for all the replies, the problem was the
> > chopper emitter
> > resistor R4110  .18 Ohm 2 watt was open so of course no signal from it
> > to U4101. The set runs with a normal picture , problem is, regulated B+
> > at Cr4116 or Collector of HOT, whichever
> > you prefer is 170 volts in standby, when running it is 143 volts??? I
> > have rechanged C4108,
> > the 5.6 v zener is perfect, all the caps in the switchmode were changed
> > the first time around,
> > I now have 2 sets in the shop with this same problem, the other sets
> > standby regulated B+
> > goes all the way up to 275 volts and yes I am using the correct ground.
> > ANY ideas??? None
> > of the parts appear to be running hot, please help if you`ve corrected
> > this problem before, tia,
> >  Larry E
> >
> >
> > Larry Eastman wrote:
> >
> > >Hi Guys, I`ve got this 169 PTA light box in the shop that`s got no
> > >secondary voltages,
> > >obviously I`ve got a problem with U4101 not driving the chopper. Set
> > >came in with fuse,
> > >R4001 surge resistor, chopper, and U4101 shorted, replaced  (with oem
> > >parts) these
> > >parts as well as C4102,4104, 4108, Cr4118 and now I don`t have any
> > >regulated B+ standby
> > >voltages. Raw B+ is at 160 volts,  checked all parts between pin 14 of
> > >U4101 and base of chopper
> > >pulled CR4116 to unload the reg. B+ to the HOT and still can`t get
U4101
> > >to send pulses to base of chopper, I have the fluctuating 7-9 volts on
> > >pin 16 of U4101 and it`s on cathode of CR4101
> > >but voltage only reads .3 volts on cathode of CR4106 and supposedly the
> > >cathodes of these
> > >2 diodes are supposed to be within 1 volt of each other, I assume this
> > >is where my problem
> > >is but can`t find it, I`ve pulled J1903 from the audio board and J1001
> > >from the PTV aux board
> > >so they are not the problem, any ideas??? I don`t have any at this
> > >point, tia, Larry E
> > >Larry Eastman
> > >American TV & Electronics
> > >Crystal River, Fl. 34428
> > >www.tvjunkyard.com

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