Help! How to Stabilize Video Monitor Picture

[Zephy]

Help! I have an old video sculpture I built in 1995. It has three 9" B
& W monitors. They were originally obtained via mail order from Herbach
& Radman - they're just a circuit board and a CRT - it takes composite
input, operates at 12V.

Well, I just sold this sculpture to someone, and need to get it working
properly again. I tested the 3 monitors; two are good but one of them
will not hold a stable picture: no matter how carefully I adjust
Horizontal hold, Vertical Hold (and V. LIN.) it rolls and shudders side
to side, changes vertical rate (I think), won't lock in.

I had a spare, never-used CRT in storage. I took it out, hooked it up
exactly like the others, and it does the same thing! So that's two out
of four that are doing this. Seems doubtful that they would have bad
components, as they have very very little use and were stored away. I
must be overlooking something.

I don't know much about video circuits, so I would really appreciate
any illuminating comments.

I got help with these monitors on this newsgroup back in 1995. The
thread can be read here:

http://groups-beta.google.com/group..._doneTitle=Back+to+Search&&d#7c92d81106c78f24

I don't have the follow-up emails with Sam Goldwasser that helped me
iron out the original synching problem in 1995, but it looks like I did
install a jumper on an IC -The IC part number is: TDA1180P. (TV
HORIZONTAL PROCESSOR). I jumpered pins 8 & 9 (Vertical Sync. Separator
Input & Sync. Separator Input).
Thanks for any help.

***** Live Long and Phosphor *****

 

[NSM]

| Help! I have an old video sculpture I built in 1995. It has three 9" B
| & W monitors. They were originally obtained via mail order from Herbach
| & Radman - they're just a circuit board and a CRT - it takes composite
| input, operates at 12V.
|
| Well, I just sold this sculpture to someone, and need to get it working
| properly again. I tested the 3 monitors; two are good but one of them
| will not hold a stable picture: no matter how carefully I adjust
| Horizontal hold, Vertical Hold (and V. LIN.) it rolls and shudders side
| to side, changes vertical rate (I think), won't lock in.

What are you using to generate the signals?

N

 

[Zephy]

What am I using to generate the video signal? Just an ordinary VCR.
Again, two of the monitors work fine, two have this unstable picture.
- Z

 

[NSM]

| What am I using to generate the video signal? Just an ordinary VCR.
| Again, two of the monitors work fine, two have this unstable picture.
| - Z

Well, if two work and two don't it's pretty sure it's the monitors.
Unfortunately at this point you really need someone with smarts and the
right equipment. I'd start with a scope on the vertical system and see what
the sync system is doing.

Be aware there's no short, simple solution for all cases. It's a matter of
working your way through the system until you find and replace as many parts
as are bad. That's why you have to train for 5 years to be qualified to fix
this stuff. TVs and monitors are complex devices.

N

 

[Franc Zabkar]

What am I using to generate the video signal? Just an ordinary VCR.
Again, two of the monitors work fine, two have this unstable picture.
- Z

Does the monitor sync with a DVD source? If it does, then I would
suspect some kind of flagwaving issue. This usually shows up as
horizontal jitters at the top of the screen. The TDA1180P IC has a
Time Constant Switch pin (12) and a Coincidence Detector pin (11)
which can be forced to accommodate VCR sources.

From the datasheet:
http://www.ortodoxism.ro/datasheets/stmicroelectronics/1191.pdf

"To optimize the behaviour of the IC if a video recorder is used, the
state of the [coincidence] detector can be forced by connecting Pin 11
to earth or to + VS."


- Franc Zabkar

 

[Zephy]

A flagwaving issue - is that related to the jingoism issue?

I couldn't get any of them to work with a DVD source (a PowerBook
laptop running a DVD - that's all I have). In any case, it's more than
jitters at the top of the screen: neither horizontal or vertical sync.
work. They roll in both direction, at increasing or irregular rates,
and there is and increase/decrease in brightness.

I noticed on the two that don't work properly that the TDA1180P IC is
getting very warm - almost too hot to touch - while with the two that
work, they don't get very warm.

I think it's time to order some of those chips. Who would you suggest
trying? DigiKey?

 

[NSM]

| A flagwaving issue - is that related to the jingoism issue?
|
| I couldn't get any of them to work with a DVD source (a PowerBook
| laptop running a DVD - that's all I have). In any case, it's more than
| jitters at the top of the screen: neither horizontal or vertical sync.
| work. They roll in both direction, at increasing or irregular rates,
| and there is and increase/decrease in brightness.
|
| I noticed on the two that don't work properly that the TDA1180P IC is
| getting very warm - almost too hot to touch

That seems odd. I wouldn't have expected those would get hot.

| while with the two that
| work, they don't get very warm.
|
| I think it's time to order some of those chips. Who would you suggest
| trying? DigiKey?

http://www.electronix.com/catalog/product_info.php/cPath/6_311/products_id/9920

shows them at $2.49 ea. But I warn you that replacing them may not be the
solution. You are still guessing. It's possible that some other part has
failed causing symptoms and overheating.

NM

 

[James Sweet]

| A flagwaving issue - is that related to the jingoism issue?
|
| I couldn't get any of them to work with a DVD source (a PowerBook
| laptop running a DVD - that's all I have). In any case, it's more than
| jitters at the top of the screen: neither horizontal or vertical sync.
| work. They roll in both direction, at increasing or irregular rates,
| and there is and increase/decrease in brightness.
|
| I noticed on the two that don't work properly that the TDA1180P IC is
| getting very warm - almost too hot to touch

That seems odd. I wouldn't have expected those would get hot.

| while with the two that
| work, they don't get very warm.
|
| I think it's time to order some of those chips. Who would you suggest
| trying? DigiKey?

http://www.electronix.com/catalog/product_info.php/cPath/6_311/products_id/9920

shows them at $2.49 ea. But I warn you that replacing them may not be the
solution. You are still guessing. It's possible that some other part has
failed causing symptoms and overheating.

NM

I would say not just possible but probable.

 

[Jumpster Jiver]

Seems doubtful that they would have bad
components, as they have very very little use and were stored away.

Some components certainly can go bad from lack of use and just being
stored away. Capacitors have been known to dry out. I would start
checking them.

 

[NSM]

|
....
| >
| > shows them at $2.49 ea. But I warn you that replacing them may not be
the
| > solution. You are still guessing. It's possible that some other part has
| > failed causing symptoms and overheating.
| >
| > NM
| >
|
| I would say not just possible but probable.

I used to get questions like this 20 years ago from people trying to figure
out their new computers. I always had the impression that they believed
there was some magic key combination known only to people like me which
would make their computer 'go', and do what it was they wanted. They never
could be made to understand that there was a whole layered series of steps
you needed to follow to get online to some data service and download
required information for example.

NM

 

[NSM]

|
| Seems doubtful that they would have bad
| components, as they have very very little use and were stored away.
|
| Some components certainly can go bad from lack of use and just being
| stored away. Capacitors have been known to dry out. I would start
| checking them.

I get the impression that these were from a surplus dealer - maybe pulls. I
wouldn't overlook drifting resistors either.

NM

 

[Zephy]

Thanks for your help and ideas. Yes I admit I was looking for the quick
fix. I'm going to need to remember my more in-depth troubleshooting
skills, limited as they are. (I worked as an electronics technician
about 20 years ago, used to do some component-level fixes of Macintosh
power supplies when I was working as a consultant, and have built small
projects). I do have a DVM and an oscilloscope, and 2 good units to
compare with. I wonder if I should invest in a capacitor checker. Kind
of makes sense that capacitors would be more likely to degrade than a
silicon chip or transistor. Would a resistor drift over time if there
were no current running through it? Yes, some of this is guesswork, but
it can be useful if in the exploration and exchange of ideas, I get
more of an idea where to focus once I get down to work.

 

[NSM]

| Thanks for your help and ideas. Yes I admit I was looking for the quick
| fix. I'm going to need to remember my more in-depth troubleshooting
| skills, limited as they are. (I worked as an electronics technician
| about 20 years ago, used to do some component-level fixes of Macintosh
| power supplies when I was working as a consultant, and have built small
| projects). I do have a DVM and an oscilloscope, and 2 good units to
| compare with. I wonder if I should invest in a capacitor checker. Kind
| of makes sense that capacitors would be more likely to degrade than a
| silicon chip or transistor. Would a resistor drift over time if there
| were no current running through it? Yes, some of this is guesswork, but
| it can be useful if in the exploration and exchange of ideas, I get
| more of an idea where to focus once I get down to work.

There are troubleshooting guides on the web, and many larger libraries will
have books on TV repair. I would start with the vertical and work my way
back trying to see if the sync system for it is working OK or not. That may
fix the horizontal as well.

N

 

[Franc Zabkar]

A flagwaving issue - is that related to the jingoism issue?

http://www.videofortes.com.br/glossary_of_video_terms.htm

Flagwaving --- The sideways pulling and fluttering seen at the top of
a TV picture caused by a skew misadjustment or some other tape tension
error.

Some early TV sets required a mod (eg a jumper wire) so that they
would sync properly with VCRs. Others had a special channel optimised
for VCR use.

I couldn't get any of them to work with a DVD source (a PowerBook
laptop running a DVD - that's all I have). In any case, it's more than
jitters at the top of the screen: neither horizontal or vertical sync.
work. They roll in both direction, at increasing or irregular rates,
and there is and increase/decrease in brightness.

I noticed on the two that don't work properly that the TDA1180P IC is
getting very warm - almost too hot to touch - while with the two that
work, they don't get very warm.

The datasheet for the TDA1180P specifies an absolute maximum supply
voltage of 15V. Is your +12V supply really +12, ie is it regulated? If
not, is it also possible that 50/60/100/120Hz ripple from your supply
is affecting the IC?


- Franc Zabkar

 

[Zephy]

I fixed both monitors. It was a bad solder joint. Was making big plans
to go buy parts, and got fed up and just started poking around
intuitively with my finger on the back of the circuit board. I touched
the jumper that goes between pins 8 & 9 on the TDA1180P and instantly
it syncs up. A few minutes with the soldering iron and both units are
working. Sometimes it *is* simple.

 

[NSM]

| I fixed both monitors. It was a bad solder joint. Was making big plans
| to go buy parts, and got fed up and just started poking around
| intuitively with my finger on the back of the circuit board. I touched
| the jumper that goes between pins 8 & 9 on the TDA1180P and instantly
| it syncs up. A few minutes with the soldering iron and both units are
| working. Sometimes it *is* simple.

Always try the easy things first. Always.

N

 

[Zephy]

Thing is, that was a new jumper I just put on the spare monitor, so it
was quite unexpected that it was not making contact. But it was a case
of soldering a very tiny wire onto the back of a PC board where IC pins
stick out, so apparently getting a good weld was harder than usual. The
installed monitor with the old jumper had the same situation. 4 things
needed to mate: solder pad, IC pin, wire, solder, and I probably didn't
use the iron long enough in my concern about overheating the IC.
However, it was fortunate that it happened anew because I was
immediately able to know what was wrong with the old one!

 

[Franc Zabkar]

I fixed both monitors. It was a bad solder joint. Was making big plans
to go buy parts, and got fed up and just started poking around
intuitively with my finger on the back of the circuit board. I touched
the jumper that goes between pins 8 & 9 on the TDA1180P and instantly
it syncs up. A few minutes with the soldering iron and both units are
working. Sometimes it *is* simple.

So why is the IC getting too hot to touch?


- Franc Zabkar