View Single Post
  #1  
Old 11-20-2010, 06:06 PM
DaveWM DaveWM is offline
VideoKarma Member
 
Join Date: Feb 2009
Location: Orlando FL
Posts: 5,607
Packard Bell console

NOS set, only two issues, vert height (50uf cap in vert circuit) and no sync (horz and vert).

the vert was easy, the sync turned into a tough dog. its a hybrid (IF/sync transistor, all the rest tube). after chasing my tail for a few days I finally checked the bias pot on the noise inverter. I cant recall if i checked this early on (its a 100 ohm trim pot) but even if I did I think I may have been misled due to its connection to a transistor in the circuit (dont recall if I swapped the meter leads). needless to say after days of putzing around I finally managed check it again. I had noticed the adj of that pot had confusing results on the scope of the sync pulse, still did not dawn on me. I think I may have been too deep into it (forest for the trees....) Anyway after a good rest I check there again and found it open. This would totally screw the bias of the noise inverter transistor and I assume it was cutting off the sync completely. A trip to the surplus store resulted in a very nice precision pot (overkill but it was the only small 100ohm pot they had). A little micro surgery to remove the old and replace with this (all in the same location so adj is easy to get at), on the PCB (there are 3 trim pots on a single board).

finally after days, and countless pulling of the chassis, I plug in and get a perfect lock. I also now see what it should have looked like all along (the sync pulse that is).

I still need to check the cathode current but other than that I can stick a fork in it. I will get a pic later.

One other thing, its a remote set, so I will be looking for a clicker for it.
Reply With Quote