At NERG my Juno First monitor decided to throw its teddy out of the pram and stop working, tried reflowing a few suspect parts on the Sunday morning but no good. Had this back on the bench and fixed it.
Here's a video discussion of the repair, test and putting it back in service.
[tube]7pqw9-hBjrw[/tube]
Synopsis: The tube would start up, you could hear deflection, you could see neck glow and we had B+ and then 12v at pin 14 of the combined drive IC (IC301 - HA11423), however, no video display would appear on screen. Nothing output at pin 5.
Tapping side of chassis reveals that the screen will briefly flicker into life and then die again indicating a broken trace or component leg somewhere.
After a number of sessions of investigation, the +15v circuit is not being completed, this runs from pin 5 around a number of components and ends up at R701 and then pin 10 on the flyback.
Tracing point to point and through each component I could not find anything broken or out of spec, several reflows were done and some bridging was done on some decaying traces but still no results.
Eventually I reached the flyback (we know this is working due to HV start etc) and found R701's output leg goes to a test point near pin 10 on the flyback, however, test point to pin 10 was open, at first I thought this was the bad trace - it would make sense that i'd have no +12v at pin 5 if the circuit wasn't being completed, however, it turns out that the pad under pin 10 had broken and was only making partial contact.
I desoldered the pin which of course removed the rest of the pad, a solid solder bridge has been placed between the next nearest component directly in line and pin 10 (pictured in the video). Tested and now working again.
The video also shows some test work and explanation and then finally the monitor is re-installed in the cab and we play the game very badly.
A crusade in my own personal learning and for the benefit of myself and those who come to the parties and those who play the machines at the various events through the year.
Enjoy, any questions or comments, feel free to ask.
Here's a video discussion of the repair, test and putting it back in service.
[tube]7pqw9-hBjrw[/tube]
Synopsis: The tube would start up, you could hear deflection, you could see neck glow and we had B+ and then 12v at pin 14 of the combined drive IC (IC301 - HA11423), however, no video display would appear on screen. Nothing output at pin 5.
Tapping side of chassis reveals that the screen will briefly flicker into life and then die again indicating a broken trace or component leg somewhere.
After a number of sessions of investigation, the +15v circuit is not being completed, this runs from pin 5 around a number of components and ends up at R701 and then pin 10 on the flyback.
Tracing point to point and through each component I could not find anything broken or out of spec, several reflows were done and some bridging was done on some decaying traces but still no results.
Eventually I reached the flyback (we know this is working due to HV start etc) and found R701's output leg goes to a test point near pin 10 on the flyback, however, test point to pin 10 was open, at first I thought this was the bad trace - it would make sense that i'd have no +12v at pin 5 if the circuit wasn't being completed, however, it turns out that the pad under pin 10 had broken and was only making partial contact.
I desoldered the pin which of course removed the rest of the pad, a solid solder bridge has been placed between the next nearest component directly in line and pin 10 (pictured in the video). Tested and now working again.
The video also shows some test work and explanation and then finally the monitor is re-installed in the cab and we play the game very badly.
A crusade in my own personal learning and for the benefit of myself and those who come to the parties and those who play the machines at the various events through the year.
Enjoy, any questions or comments, feel free to ask.
