25k7401 diagnosis help...

[castlesteve]

Ok so I have a wells 25" 7400 series monitor.  It really looks new and the colors are great.  I havent done a cap kit (yet)... but that really isnt my problem.  The colors look brilliant and I have a ton of adjustment in contrast and brightness without color wash.

My problem is that  I have a strange positioning problem where I cannot get the bottom of the display right.  It is squished in the middle and separates vertically at the top.   From the pictures, you can see it... the blur is from my camera... the picture really is nice otherwise.

I have tested the pots and they all look good.  The vertical position pot is fine and all the way open (4 ohm)... so its thats not the problem.

also, I adjusted the large coil pot... and it doesnt seem to do anything... at all.  I thought that was a horiz coil... so even though i dont see any change in that pot, that SHOULDnt be it?

I have a strange little vertical board mounted on the main board.  I think it is the pin cushion adjustment (right).  That of course was no help.

I tried another known working cable....

What else do I have?

Thanks,
Steve

[modessitt]

Ken Layton addresses this problem in another post several spots down.

"The "squishing" problem is called "foldover" and the vast majority of the time it's caused by bad electrolytic capacitors."

Always do the cap job anyway when you have a display problem just to eliminate that possibility, no matter how good the colors look.  Caps do more than just control colors.

[castlesteve]

Thank you.  I guess I probably should have searched more for squished. 

I'll go do those caps...

Also, I read somewhere that IC2 and perhaps IC1 could be also a culprit... Do you think in this case.  I do have an older 7193 board I have been using for parts salvage... I guess I can look to see if they use common ICs

Thanks again for your quick reply
Steve

[modessitt]

Try the cap kit first and see how it looks. 

A lot of fixes list IC's to change out on various monitors for various boards, but I've found that I rarely ever need to change an IC unless the board had a serious overload, or the monitor has a known design defect that needs the change.  Usually the culprits will be some type of capacitor, transistor, flyback, resistor, or diode, usually in that order, coupled with bad solder joints.  I usually wait on changing IC's as a last resort if everything else seems to be okay and it's still messed up.

[castlesteve]

I just picked up a capkit and will try it tonite (if time allows).  I'll post back my results.

Thanks!

[castlesteve]

UPDATE:

I will never doubt the cap kit again!   It of course solved my foldover problem.  Of course, I had to suppliment the standard capkit with some that were missing.  Powered it up this morning and other than some readjustments... worked perfectly

Thanks again for steering me straight.   

[Ken Layton]

This model has been out on the market long enough now that it is certainly old enough to need new capacitors. Remember also that Wells-Gardner uses the shittiest "bottom-of-the-barrel" capacitors out there.

[modessitt]

Glad it worked!

[castlesteve]

I did notice that the capkit appears to have been a WG... also containing ---smurfy--- parts.  Oh well.. should have bought from arcadeshop.   This monitor is mine so it doesnt see a lot of ON time anyway.  Hopefully I wont have to cap it again for quite some time (unlike the latest WG monitors).

-s

[BadMojo12]

Hey; someone is selling this monitor on craigslist and I can't find any info on it; is this monitor a multisync?  How is this monitor performing with mame?

Ryan

[Kevin Mullins]

http://www.wellsgardner.com/pdf/Spec/K7400_25.pdf

[Ken Layton]

Hey; someone is selling this monitor on craigslist and I can't find any info on it; is this monitor a multisync?  How is this monitor performing with mame?

Ryan

NO! 

Standard resolution only.