[TechAssist] Re: RCA Projection PTK169PTA U4101 problems (no standby voltages)
- From: "Electric Medic" <info@xxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Wed, 1 Oct 2003 17:40:45 -0400
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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mailto:info@xxxxxxxxxxxxxxxxx
-----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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