[TechAssist] Re: RCA Projection PTK169PTA U4101 prob. (no stdby voltages)FIX?
- From: Larry Eastman <videotech@xxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 03 Oct 2003 12:18:58 -0400
Bob, standby regulated B+ should be approx. 140 volts not 170 right ? I
replaced CR4122
C4141 checks good for leakage and esr, C4151 checks good , voltages on
Q4105 are
perfect, I`ll check around the error amp circuit. The strange thing to
me is that nothing runs
hot when I run the set, but I don`t want to send it out and have it fail
in a week, thanks for
your reply, Larry E
Larry Eastman
American TV & Electronics
Crystal River, Fl. 34428
Gemini Computer & TV wrote:
>Larry,
>The one you have fixed sounds very normal to me for standby and run B+
>voltages. For the others with B+ at 275 volts (you say you replaced the
>regulator IC and associated caps already), check the following components:
>CR4122 (3v, 1watt zener diode, RCA# 200158)
>C4141 (470mfd/180v)
>C4151 (1000pf, 50v, RCA# 181460)
>Q4105 RCA# 143802 (and other transistors in this error amp circuit).
>
>Bob Waterman, CET® #RI-28
>Master Technician License #9109
>Service Manager / Parts Manager
>Gemini Computer, TV, & Security Alarms
>(508)695-7302
>(508)695-7769 FAX
>geminitv@xxxxxxxxxxxxxxxx
>geminitv@xxxxxxx
>www.geminicomputertvsecurityalarms.com
>
>
>----- Original Message -----
>From: "Larry Eastman" <videotech@xxxxxxxxxxxx>
>To: <techassist@xxxxxxxxxxxxx>
>Sent: Friday, October 03, 2003 9:42 AM
>Subject: [TechAssist] Re: RCA Projection PTK169PTA U4101 prob. (no stdby
>voltages)FIX?
>
>
>>Al, have changed that cap twice in both of the sets I have, Larry E
>>Larry Eastman
>>American TV & Electronics
>>Crystal River, Fl. 34428
>>
>>al m wrote:
>>
>>>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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