7854 power supply disassembly


Alberto, IZ2EWV
 

Hello friends,
The 7854 that I recently bought, after some minutes of operation started emitting a whistle, a burst, some smoke from the rear ad an awful burning smell... "as usual!" I thought, remembering the past experience with my 7904A, in which the problem was in the AC filter. But here the bad component is the RC snubber C5 in the A23 switching board.
The problem is: how to disassemble the A23 board from the A12? I tried to unscrew the A12 from the chassis and the rear heatsink, hoping that it could come with the transformer, but some wires of the latter are soldered to the A23 board!
Anybody could explain to me the easier way to separate the two boards? I would like to avoid to make disasters, considered that I have to replace only one component! And the wires of the transformer and the other coils are leaving me afraid.
I'm not the kind of who cuts the bad part and solders the new one by the component side of the board, or simply bypasses it, so I need to know how at Tektronix they service this board.
Thank you in advance,
Alberto, IZ2EWV

Join TekScopes@groups.io to automatically receive all group messages.