CRT monitor vertical deflection problem

G

G B

Guest
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
 
On Fri, 5 Feb 2010 19:01:35 -0600, "G B" <geeberry@frontiernet.net>
put finger to keyboard and composed:

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:
----____ ----____
--- | ----------------------
------
| | | |
| | | |
|__-- | __---
Click to expand...
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
Click to expand...
The applications in the datasheet all show sawtooth inputs.

http://forums.futura-sciences.com/attachments/depannage/59239d1225292469-television-dalco-panne-stv9302a.pdf

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


- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message news:kb0qm51ud2sedim8ah7uatm55hj2svhagp@4ax.com...
On Fri, 5 Feb 2010 19:01:35 -0600, "G B" <geeberry@frontiernet.net
put finger to keyboard and composed:

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/attachments/depannage/59239d1225292469-television-dalco-panne-stv9302a.pdf

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


- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Click to expand...
Franc,

Thanks for your response. I figured the ASCII art wouldn't work. I will try to format it in Courier New 8 pt. as you suggest:
----____ ----____
--- | ---------------------- | ---
| | | |
| | | |
|__--- |__---

It is supposed to look more like a negative going pulsed dc waveform. There appears to be a little overshoot at the positive egdes. The base of the pulse appears to be slightly increasing as well.

I knew the data sheets show a ramp/saw waveform. I assumed that is what I would measure here to provide a constant sweep down the screen. I don't know if this is actually how the deflection is used in this TV. But lets assume it is since CRT's are very similar anymore...

What I was really more interested in is if the ASIC uses a capacitor to generate the ramp. I have been examining other 64 pin ASICs and they seem to have a pin very close to the VOUT which is a cap. I wonder if this cap went bad, if it might generate the above waveform. This of course assumes the ASIC I examined works similar to the one on this board. It also assumes a similar pinout..etc.

Thanks for the help.

-Greg
 
G B wrote:

Franc,

Thanks for your response. I figured the ASCII art wouldn't work. I
will try to format it in Courier New 8 pt. as you suggest:
----____ ----____
--- | ---------------------- | ---
| | | |
| | | |
|__--- |__---
It is supposed to look more like a negative going pulsed dc waveform.
There appears to be a little overshoot at the positive egdes. The
base of the pulse appears to be slightly increasing as well.

I knew the data sheets show a ramp/saw waveform. I assumed that is
what I would measure here to provide a constant sweep down the
screen. I don't know if this is actually how the deflection is used
in this TV. But lets assume it is since CRT's are very similar
anymore...

What I was really more interested in is if the ASIC uses a capacitor
to generate the ramp. I have been examining other 64 pin ASICs and
they seem to have a pin very close to the VOUT which is a cap. I
wonder if this cap went bad, if it might generate the above waveform.
This of course assumes the ASIC I examined works similar to the one on
this board. It also assumes a similar pinout..etc.

Thanks for the help.

-Greg
Click to expand...

Dump the HTML. Usenet is a text medium.


--
Greed is the root of all eBay.
 
On Fri, 5 Feb 2010 19:01:35 -0600, "G B" <geeberry@frontiernet.net>
put finger to keyboard and composed:

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 ...
Click to expand...
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
--
Please remove one 'i' from my address when replying by email.
 
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