[TechAssist] Re: RCA Projection PTK169PTA U4101 problems (no standby voltages)
- From: Larry Eastman <videotech@xxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 01 Oct 2003 18:34:47 -0400
Perry, thanks for the reply, I have the manual and I`ve worked on quite
a few of these
but I`ve never seen one with this problem, I`ve checked R4150 and the
zener and both are good
I believe the problem is with the feedback pulses, I`ve changed U4101
twice with oem parts
I read on another site that cr4106 is supposed to have approx. the same
voltage on it`s cathode as cr4101(10.5v) but cr4106 has .3-.6 volts but
the diode checked good (changed it anyway)
still has the same problem, I`ll keep at it and post the fix when I find
it, thanks, Larry E
Electric Medic wrote:
>Larry:
>
>Pin 16 of U4101 is low and or not stable.
>
>Here are the standby voltages for the regulator IC U4101.
>pin 1 0.03V PWM Control
>pin 2 0.27V Duty Cycle Control
>pin 3 0.06V Current Sense
>pin 4,5,12,13 GND
>pin 6 2.30V E in
>pin 7 2.88V S in
>pin 8 0.01V C2
>pin 9 1.13V Slow Start
>pin 10 2.50V C0
>pin 11 10.8V R0
>pin 14 0.58V Output
>pin 15 10.9V V+
>pin 16 10.8V Vcc
>
>If you supply 10.8 volts to pin 16 of U4101 does pin 14 of U4101 output the
>correct
>waveform?
>
>Check the value of all the components that are connected to pin 16. Check
>R4150 (22 ohm surface mount) it will keep pin 16 low. U4101 should start
>around 10 volts. Also check CR4122, 3v zener.
>
>Perry Bower, (EHEER) Electronic Home Entertainment Equipment Repairer
>Electric Medic
>"It's Cheaper to Keep Her"
>http://www.electricmedic.com
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>3850 Washington Road Suite 5b
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>
>
>-----Original Message-----
>From: techassist-bounce@xxxxxxxxxxxxx
>[mailto:techassist-bounce@xxxxxxxxxxxxx]On Behalf Of Larry Eastman
>Sent: Wednesday, October 01, 2003 5:05 PM
>To: techassist
>Subject: [TechAssist] RCA Projection PTK169PTA U4101 problems (no
>standby voltages)
>
>
>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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