Commodore 1960 monitor

[mechy]

Is this unfixable?  I can take it all apart and look, but, need to know what I am looking at first.  What is the white cylindrical component that has the burns around it?

I fixed said monitor,and it was a nightmare. If you aren't familiar with these monitors please don't mess around in them. There lethal high voltages. Most cases they can be repaired but finding someone to take it on these days is tough. If you find someone,bring them the schematics.

[mechy]

Sorry to resurrect this thread, but I think it is time to try and repair   this monitor.  For the last few years, I've been more into arcade cabinets than Amiga.  I've repaired quite a few arcade monitors during this time.   This monitor is different, though, since it has its own SMPS versus relying upon an isolation transformer built into a cabinet.

Several times in this  thread, @mechy mentioned the FET being an issue in the ones he's repaired.   @mechy , are you referring to Q403 (a 2SC4123 located on the heatsink/shield immediately next to the flyback transformer)?  Is this transistor the HOT?   I've pulled this transistor and tested it via a diode test on my multimeter, and it is shorted.  What I've learned from arcade monitors is that if the HOT is shorted, there's a problem somewhere else that is causing it.  Where to look next?  I plan on first recapping things,  but, if it's the flyback that's out, is that an unobtainable part?

Thanks!

Sorry,i am not a expert by any means on this monitor.. this was 15-20 years ago,i recall i replaced the transistor with a cross..irf640? 680? 840? i dont recall. I can't tell you if it was Q403 but i seem to recall is was somewhat in the middle of the board?.Seem to remember some bad diodes i replaced and caps. Sorry i can't be of more help! i see a flyback here,page claims to be updated but looks..eh?  https://www.technotronic-dimensions.com/Products2c.html

It lists some flyback numbers that could be searched elsewhere maybe.

[kirk_m]

I've got a new flyback on order as well as a replacement HOT (ordered it a few days ago from that particular supplier).  I've checked all the diodes on the board, and none are bad.  I'm very familiar with monitor voltages, I've repaired 20-30 arcade monitors in the last few years.  I still have to make a cap list and perform a recap.  I'll update the thread as I move forward with the repairs, and I hopefully have a lead on an original copy of schematics, versus all the poor quality scans of them on the web.

[mechy]

Good luck,it will be interesting to see what you find! I hope you get it fixed.

[kirk_m]

Swapped out the FBT and the HOT today...no change.  The power LED blinks quickly, and, I have no B+ voltage at TP4.    What else should I be looking at?

[kirk_m]

I am recapping the monitor...so I compiled a list of all 54 caps as I removed them from the main chassis and the neck board.  Maybe this might help someone else resurrect one of these monitors.  The list is attached to the post.

[kirk_m]

Recapping  didn't fix the problem, neither did replacing the HOT or flyback.  Likely,   these parts were all still good, unfortunately.   I should  have  known that the issue was with the SMPS, because  even with the old components, the power led would flash on and off rapidly,  and a very, very  faint  ticking could be heard if  I were to  work on it in an extremely  quiet  room.  I began  checking the DC lines and eventually found that D805 was shorted.  Replacing it  with an identical fast recovery diode of required  rating brought it back to life.  HV immediately appeared, and I adjusted the B+ trim pot, now have a solid 86V B+.  Just a few tweaks to focus and screen controls were all that were needed.  The monitor lives again after nearly 6 years of being dead.

[Jeff]

@ kirk_m

Congratulations - Good Work! Your thread will no doubt help others on into the future as well.

Happy Year Year!