W/G monitor problem

[68ragtop]

Hello,

[menace]

first things first! make sure you don't keep turning it on--its burning a line into the center of your tube--yes you have a vertical deflection failure.  You might wanna check for any broken joints or loose connections on the chassis before doing anything else. 

On the 7191,  replacing IC2 solves alot of vertical deflection problems--Ken L or monitor guru could likley tell you exactly what to do with your model (not that there too much difference i don't think).

[Ken Layton]

The vertical deflection IC is a common failure on these monitors. Be careful when removing the old one from the board as the copper foil traces are delicate.

Of course you may have a simple problem like the yoke conector has come unplugged or has bad solder joints.

[68ragtop]

Thanks for the info!  Is the IC2 identified on the board or, in a service manual?    I don't have a manual for the monitor.   
I will order the IC & a cap kit for it as well & see what happens.   Does the forum board sponsor sell these parts?   I aslo need to get some T-molding & a few micro switches.

68

[Ken Layton]

Visit this site: www.jstookey.com/arcade/WG_25k7191/

[68ragtop]

Well, I replaced the IC2 chip, & Also installed a cap kit while it was apart.  reflowed many solder joints on the main board & CRT board.
Unfortunatly, with no luck.  Same problem is still there.   Any other thoughts?

Thanks, 68

[dabone]

Taken from the trouble shooting flowchart.

You have a vertical deflection problem.
Test for +24VDC at IC3, pin 6.
If missing, R91 may be open.

Substitute IC3, IC2, Replace C50.

If you can't center the picture, replace transistor Q9.



Later,
dabone

[Ken Layton]

Capacitor C51 which is a Tantalum .68 uf @ 35 volts, may have opened up or radically changed in value which causes vertical failure. This cap is NOT included in capkitsbut is now failing often enough that it should be included. It is located directly behind the 50/60 hz trimpot.

[68ragtop]

Thanks again guys,   I hadn't been able to get back to working on the machine until today.  I tested IC3 @ pin 6 and have 25.6 VDC.  Should I just replace C51?  I am obviously a novice at this, & really appreciate everyones help.  I really enjoy working on this kind of thing.  Its very rewarding when the problem is solved.   In the mean time, I will check various voltages according to the service manual, & see if I can find anything out of range that way.  Is there anything that could have happened to the CRT, or other components from the drop I mentioned?
Or is that not likely?

Hope everyone has a great Holiday!

68ragtop

[dabone]

Just for fun, have you checked for continuity from the board to the yolk?

Later,
dabone

[68ragtop]

Thanks for quick response!

I will check that next!

[Ken Layton]

It's possible there could be cracks around the solder of the yoke connector pins, but I would examine the foil side of the board very closely for cracks/breaks first. Capacitor C51 is very delicate and if it's gone open you'll lose all vertical deflection. The value of it is critical. C51 only costs around $1 retail.