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 ***************************************************************************** Classifieds! Buy or Sell! http://sell.tech-assist.org The Tech Address Book: http://www.tech-assist.org/secure/tip/contact.htm Add a Repair Tip Here, or Change/Remove your Email Address: http://www.tech-assist.org/secure/tip/main.htm Lost Password: http://www.tech-assist.org and select "Lost your Login Info?". Email Archives: //www.freelists.org/archives/techassist/