Makvision M3129 27" Tri-Mode Monitor

[tnarv]

Our company has many of these Makvision 3129 27" Tri-Mode Monitors but I haven't seen this problem before. The SMPS fails to start up. Have raw B+ on primary side of Swithch Mode transformer and also to the SCR. I believe the SCR is "gated" on by the 8-pin IC1. I haven't changed the IC yet as it's soldered in and kind of difficult to remove. I've noticed some posts on these chassis's but not for this problem. Anyone out there have any experience with this particular problem? If not, is there someone out there who repairs these particular chassis?Suzzo Happ used to repair them but no longer do. Any help would be more than appreciated.

[grantspain]

had a few with blown resistors, diodes in the secondary- and yes that ic does fail, also seen the diodes in bridge fail and the FET short

[tnarv]

thanks so much for your reply. Problem Solved! Even though this chassis is very new and not many hours on it I managed(before I threw it against the wall)to find a bad Electrolytic Cap. in the KA3845B SMPS Contoller circuit. Replaced C10(220uf 25V.)Capacitor. The caps used in this version are as bad(or possibly worse) as the ones used previously. They're made by Jun Ru I believe and this chassis is full of them. Not replacing them all at the moment, I'll deal with them as they fail. Proof that, even though these caps looked pristine, they can be bad. All is good. Hope this helps someone down the road who is working on one of these "monsters."

[grantspain]

you should also consider replacing all the 10uf 400v caps
when i repair these i replace all caps in power supply and vertical circuit

[tnarv]

Thanks for the tip on the other caps. I will definitely change the others too. That, hopefully will help extend the life of the Horiz. Deflection and Vertical Output circuits. Appreciate it.