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    Fm3 coupling capacitors

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    Dynalover

    Posts : 12
    Join date : 2010-09-08
    Age : 52
    Location : Waterloo, Ioway

    Fm3 coupling capacitors

    Post by Dynalover on Wed Sep 08, 2010 9:22 pm

    As Bob has noted, the FM3 tuner may not be the most high performance tuner out there, but it sure sounds good when set up right. To that end on this unit have started in and replaced all the electrolytic filter capacitors in the power supply, new rectifier, and replaced other (very) weak tubes, cleaned the controls, sockets, tuning cap, etc.

    Noticed that I don't have some of the larger values of the coupling caps like .22 in stock, but did change the audio coupling caps w/ a pair of 600 volt sprague 716. Thing is though, the original capacitors show no leakage at full voltage on my eico bridge, so they must be more modern type poly? Should I go ahead and change out the rest, or are these red/brown guys OK? Not sure what year this unit is, the caps replaced are 0.1uf @ 400 volts, brown dipped type marked "GI" ? Looks like it is recommended to bump the value of these up to .22 as well?

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Fm3 coupling capacitors

    Post by Bob Latino on Wed Sep 08, 2010 9:37 pm

    One of the best FM-3 "photo essay" restorations was done about a year ago by Bill Thomas over on the Vintage Circles on the AudioCircles. The link is below. Bill has been an FM-3 fan for many years. Check the link below if you have an FM-3. Many good ideas about restoring and upgrading your Dynaco FM-3.

    Bill Thomas Dynaco FM-3 restoration link

    Bob

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