Proline 28N1 - Picture vanishes

[msu]

Hello,

I have a 5 year old Proline 28N1 with a problem that picture vanishes for a few seconds to minutes then it comes back automatically. A little tapping on the chassis may help recovery. This is an intermittent problem. May happen frequently (a couple of times per day) to once in weeks.

This problem started about three years ago. At that time a loose solder was diagnosed and repaired but now it has comeback.

Any suggestion which solder may be the culprit? or should I look for some other problem?

Thanks in advance for assistance.

Note: To my understanding Proline 28N1 is same as Bush 2850 (whose basic circuitary is available on this forum).