[TechAssist] RCA Projection PTK169PTA U4101 problems (no standby voltages)
- From: Larry Eastman <videotech@xxxxxxxxxxxx>
- To: techassist <techassist@xxxxxxxxxxxxx>
- Date: Wed, 01 Oct 2003 17:05:10 -0400
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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