CRT monitor vertical deflection problem

[G B]

I have a TLC 14001 NTSC monitor that has a vertical deflection problem. The
horizontal deflection is working fine. The display starts 2/3 down the
display and continues off the bottom of the display. I have probed B+, 14+
and 14-, and all appear solid. I found a STV9302A vertical deflection
amplifier and I have probed the input signal. (Pin 1). I expected to find a
ramp waveform, but instead I see something that looks like:
----____ ----____
--- | ----------------------
------
| | | |
| | | |
|__-- | __---


I followed the input signal back to a TCL-A32V02-TO (8852CSNG5PF4) 64 pin
ASIC. It appears to be manufactured by Toshiba due to the 885xC part number
(I am guessing). I removed the resistor between the pin on the ASIC and the
vertical deflection amp inp to isolate it. When I probed it, it still had
roughly the same shape as above maybe without the bounce after the edges.

So questions... does anyone have any information on the above ASIC? Should
the signal that drives the 9302 be a ramp? I assume it should be a 16msec
period. If it does make a ramp, does it use an external cap to act as a
integrator make the above signal? Does anyone know of a similar ASIC/TV
that might give me clues? Am I even in the right area? So many questions..
so little info.

Thanks in advance,
Greg

 

[Franc Zabkar]

I have a TLC 14001 NTSC monitor that has a vertical deflection problem. The
horizontal deflection is working fine. The display starts 2/3 down the
display and continues off the bottom of the display. I have probed B+, 14+
and 14-, and all appear solid. I found a STV9302A vertical deflection
amplifier and I have probed the input signal. (Pin 1). I expected to find a
ramp waveform, but instead I see something that looks like:
----____ ----____
--- | ----------------------

I can't make out your ASCII art. Try using a fixed width font such as
Courier New.

I followed the input signal back to a TCL-A32V02-TO (8852CSNG5PF4) 64 pin
ASIC. It appears to be manufactured by Toshiba due to the 885xC part number
(I am guessing). I removed the resistor between the pin on the ASIC and the
vertical deflection amp inp to isolate it. When I probed it, it still had
roughly the same shape as above maybe without the bounce after the edges.

So questions... does anyone have any information on the above ASIC? Should
the signal that drives the 9302 be a ramp? I assume it should be a 16msec
period. If it does make a ramp, does it use an external cap to act as a
integrator make the above signal? Does anyone know of a similar ASIC/TV
that might give me clues? Am I even in the right area? So many questions..
so little info.

Thanks in advance,
Greg

The applications in the datasheet all show sawtooth inputs.

http://forums.futura-sciences.com/a...225292469-television-dalco-panne-stv9302a.pdf

http://jp.ic-on-line.cn/IOL/datasheet/stv9302a_382931.pdf


- Franc Zabkar

 

[Franc Zabkar]

I have a TLC 14001 NTSC monitor that has a vertical deflection problem. The
horizontal deflection is working fine. The display starts 2/3 down the
display and continues off the bottom of the display. I have probed B+, 14+
and 14-, and all appear solid. I found a STV9302A vertical deflection
amplifier ...

AFAICT, pin 7 adjusts the vertical position. Is its DC level around
0V?

There should be a low ohm resistor (eg 1 ohm) at the bottom end of the
yoke circuit. The voltage across this resistor should be proportional
to the vertical deflection current, ie it should be a sawtooth.

- Franc Zabkar