FM-3 ? About parts replacement in IF stages

0 Members and 1 Guest are viewing this topic. Read 773 times.

benken

  • Newbie
  • Posts: 1
FM-3 ? About parts replacement in IF stages
« on: 16 Oct 2011, 08:46 pm »
I got this tuner in the 70’s but stopped using it because of poor  performance have decided to restore it. Have read several articles on restoration but not much on the if stage. I would like to replace all the cap’s and resistors but don’t wont to mess with the  factory 10.7 Mhz setting. should I avoid the  T1 area I notes that one of the slugs on T4 is not adjusted should that  area be avoided?     

atmasphere

  • Industry Participant
  • Posts: 44
Re: FM-3 ? About parts replacement in IF stages
« Reply #1 on: 2 Nov 2011, 03:25 pm »
You would do well to get a copy of the manual. FM-3s do need occasional alignment! However there is a fairly simple procedure that allows you to do most of the IF stages without instruments. In fact you can also align the front end as well as long as the 'seeing eye' tube is working OK.

The ratio detector (the last transformer on the IF board) will require some instruments for proper alignment. Information on this and the stereo section is in the manual.

The unit suffers from poor grounding and quite often the 2 watt 10K resistors on the IF board can give you problems. The glue that holds the wire to the forms inside the IF transformer cans goes bad, so if you have troubles getting the alignment of the IF cans to work this may be why. I have removed the cans from the board, disassembled them and reglued the windings. Its not hard but requires patience.