MS9-29A unstable picture

[geekmiki]

Hi,

About 6 months ago I had a problem with my MS9-29A in an Astro City, the picture was unstable in one corner and was vibrating. I replaced all the caps (but one - B+ filter cap - C911 - 1000uf 200v) and in the process found the culprit that was leaking. Everything was working fine until a couple of weeks ago. Now, on a cold start, the picture slightly expands/contracts itself during the 5 first minutes until everything has heated up.
I replaced the B+ filter cap yesterday, thinking that it could be related to that and checked that the B+ was correct (76V). No luck, on a cold start, still the same problem.
I suspect that it could be B+ related, but where should I start looking now.

Any help is welcome.
Thank you in advance!

 

[Derick2k]

Sounds like bad solder joints. Its time for a checkup of them joints and resolder/reflow them.

Inspect the following,

Connectors, like:

• Voltage Input
• Signal Input
• Remote Adjustment
• Yoke
• Frequency plugs

Also check the big components/items:

• Flyback Transformer
• Big transistors
• Transformers
• Coils

Inspect the neck board (carefully) as well for bad caps, etc...

Basically any component/connector that generates a lot of heat should be inspected.

As always, be careful and discharge your tube and any large caps.

 

[twistedsymphony]

check the width/height adjustment pots. chances are it has some corrosion or possibly a crack

if you tweak the adjustment and it jumps around instead of moving smoothly chances are it's bad.

you can sort of fix corrosion by wiping the pot through the full range a few times with a little bit of pressure but if that trick doesn't work just figure out the value and replace it.