I toasted my 8liners chassis. Trying to repair.

[M.Lanza]

About 2 or 3 months ago I got a wei-ya 1220h from 8liners and
connected it to an old t.v. tube.

I didn't have a working isolation transformer at the time and thought
that it probably needed one, but I decided to try it out anyway without one.

It worked fine for a couple of hours untill the bottom half of the picture
started sucking up toward the center of the tube and shortly after suffered
what I think may be vertical collapse where the entire vertical portion of the
video display had condensed into a single horizontal line through the center
of the tube.

I looked over the chassis and nothing seemed to be obviously toasted
so I just assumed that the video processor IC HA11235 was fried.
I just got around to ordering another yesterday along with an isolation transformer.


Is there anything else on the chassis that I should replace, or should I
wait and see if the new IC remedies the problem first?

[Ken Layton]

Yes the 1220H REQUIRES an isolation transformer. It also uses a "low impedance" yoke.

The IC you mentioned would likely NOT be the problem. You'd want to look at the "vertical output" IC instead. They usually have an "LA-78xx" part number on them and are bolted to a big aluminum heat sink to dissipate the heat.

[M.Lanza]

Alright, Thanks.

I guess I'll be on the lookout for a LA7833 then?

[Ken Layton]

Yes that is correct. MCM Electronics has it and I think Bob Roberts should too.

That IC crosses to an NTE 1773 also.

[M.Lanza]

I just finished ordering one.

I guess I should have asked before ordering the other one.

At least it didn't cost too much.

[TOK]

That was my first major arcade screw-up. I had an old monitor out of a Karate Champ with a hacked up harness.
I rigged up a cord directly from the wall to test it out. Mine didn't last as long as yours though, in fact, it lasted about 5 seconds before emitting a huge flame a cloud of acrid black smoke.
My garage stank for hours.   

[M.Lanza]

That was my first major arcade screw-up. I had an old monitor out of a Karate Champ with a hacked up harness.
I rigged up a cord directly from the wall to test it out. Mine didn't last as long as yours though, in fact, it lasted about 5 seconds before emitting a huge flame a cloud of acrid black smoke.
My garage stank for hours.   

I guess as long as I learn something, it was worth it. 

I just changed out the la7833 and nothing has changed.

I really don't know what I'm doing, I'm going to pull out the chassis
again and swap the HA11235 and see if that helps.

[Ken Layton]

It could have internally damaged a resistor, capacitor, diode, or transistor from not using the isolation transformer.