This is my first posting here. I am thankful for this fine Dynaco forum.
My FM-3 amateur project was previously posted 8/8/2012 on Audio Asylum>Dynaco-doctor
Yes, Bill Thomas (RIP) was a great friend to us Dynaco folks.
Time-arithmetic suggests that he was posting & helping while dealing with fatal disease.
And then his great postings stopped...
I lack experience with the new combined-circuit board or psu from
FM-3 zone but I am a very happy previous customer there.
Perhaps a new combined board avoids many typical FM-3 probs&difficulties?
I used an SDS psu board----it is a tight fit.
I only entered the "different" FM-tuner world because of my marginal FM-3 and the
desire to round-out my Dynaco experience. Reading the Bill Thomas articles
on PC-7,PC-8,PC-12 boards greatly helped with understanding the FM-3 manual.
Rebuilding the 3 PC boards is do-able----but it was much more challenging
than my PAS3X or ST70 projects. I cant easily measure 10.7MHz and the FM-3
required much more dexterity,patience,calm-attitude,hemostats,magnifier,mirror,understanding...
More difficult---but still rewarding.
Some FM-3 rebuild thoughts:
1) optimize the FM antenna because it sources the totsig
2) alignment was the last and clearly MOST productive task I did----and much easier than expected
3) heat dissipation requires 4 taller feet and more chassis vents
4) the total-signal seems most accessible/familiar for our upgrade in the PC-12 stage
I was afraid to "improve" components in the high-freq PC-7 or intermed-freq
PC-8 stages. And how to compensate thermal variation? Unwanted inductance?
5) tube-socket hygiene is under-estimated improvement here----higher heat seems to
fuse/oxidize tube-pin "dirt"
6) time,money,nervous&tedious work on this older less-sensitive FM-tuner was
questionable(compared to my SONY XDR-F1HD) however I love Dynaco and
its tube sound---Telefunken 12AX7 in PC-12 of course!
7) I choose electrolytic caps based on lowest ESR,select tubes with my B&K747B,
improve Dynaco-specified resistor-tolerances of 5% with <1% matches(Fluke 83)
I reflow most old solder joints----esp if they seem un-shiny
9) ensure all AC wiring(including tube-heater wires) is separated from signal wires and/or
crosses them at right-angle
10) ensure tube-shield grounding
FM-3 posts seem rare on this Dynaco forum?
Best of luck on your rebuild.
I found www.fmtunerinfo.com very interesting---they call them tunas!
ps: I wish we fans could buy a black t-shirt(cotton size L)
with the DYNACO logo on it