Second MS8-29

[cruzlink2]

This one was working fine for a year and a half at my friends arcade and one day just lost image. I cleaned reflowed and recapped, also replaced 3 of the smaller transistors on the b+ circuit and managed to get an image but it was scrambled. Not sure if I should further replace the HOT and the big VR, I took off all the assystant boards and checked them and did not find anything wrong with them. I made sure to test all the transistors on the sync assys board and they all tested fine and so did the resistors on the same board. Any help would be appreciated .

[grantspain]

whats the b+ running at?

[cruzlink2]

Last time I measured while it was like this 89V used the TP1 and TP2 ground.

[cruzlink2]

This is the last one I have left to fix, hopefully someone is seen this issue before.

[grantspain]

i have had odd sync issues with the custom sync module, transistors will read good but fail under load
i know its a daft question but is the frequency jumper in the correct position?

[cruzlink2]

Yes it was on 15khz chassis was working for a whole year before it did this suddenly, I recapped and reflowed the entire thing because it would have this scrambled image for a while then no image. After the recap reflow and swapping 3 of the small transistors in the B+ area it would stay on but the image remained the same. Like you said I also took off the sync module and all the transistors there tested fine, I wonder if like you they are failing under load. Do you have the model # of the transistors by any chance? I would not mind replacing them all. I am also thinking of replacing the HOT and bit Regulator to be safe. Thanks for your help.

[grantspain]

nothing to do with HOT and regulator
if you have another ms8-29 swap the sync module to prove

[cruzlink2]

The first chassis I got working is in use at the arcade so I didn't want to pull out it's sync module to try this out, I finally got some replacement transistors that were equivalent to the originals and installed them.
I will try the chassis hopefully next week on a slow day at the arcade, hoping this is it.

[buttersoft]

that's an interesting approach! If it works, i'm sure people will be interested in the specs.

[cruzlink2]

Updating this finally, not only did I replace the transistors on the Hsync board but also the HA11423 just in case. Linked a video of the chassis after the fix.
https://youtube.com/shorts/tDMeg_DwU_E?feature=share