0 Members and 1 Guest are viewing this topic. Read 56544 times.
December 18th, 2008 - Update: "A Little Bit of History!" Dynaco's FM-3 tuner is a thoroughly REMARKABLE piece of electronic engineering. Not because it provides the highest sensitivity of any tube-based FM tuner (It doesn't!) Not because it has greater ability to separate closely spaced signals on the FM band. (It doesn't do that either!) So why on earth would ANYONE be interested in such a tuner? Because it is one of the most truly *musical* tuners on the planet! So, is *that* what makes it so remarkable? Nope! What makes the Dynaco FM-3 tuner so thoroughly remarkable is that ANYONE who is able to solder can build one from scratch, and then completely ALIGN it with absolutely NO test equipment of any kind! Now *that* is TRULY remarkable. Of course, it doesn't hurt that a properly constructed and aligned tuner simply sounds SO good! The FM-3 tuner was actually an update of Dynaco's FM-1 tuner. The FM-1 was introduced in 1961 as a monophonic tuner. It was based on a design by Stewart Hegeman, and Ed Laurent (the "father" of so many of Dynaco's "classic" tube components) made the design a reality. It featured a brass face plate and brown plastic knobs, very similar in styling to the PAS-2 preamplifier. In kit form, the FM-1 sold for just $79.95! (That's $560.05 in today's Dollars.) If you weren't very good at soldering, you could purchase a factory-wired version for $99.95 ($700.15 in today's Dollars.) The FM-1, while a Monaural tuner, was designed with Stereo in mind. Space was reserved on the chassis to add one of two "accessory modules." One of those modules was a 17 Watt amplifier module that turned the FM-1 into a complete table-model radio - all you had to add was a speaker. But the other module was a multiplex adapter that turned the Monaural FM-1 tuner into a complete Stereophonic tuner. It was pretty easy to tell which module Dynaco had in mind. The metal plate that covered the hole in the chassis had "reserved for multiplex adapter" printed on it! The multiplex adapter was designed by Sid Lidz and provided greater than 30 dB of separation. This may not sound like a lot, but back "in the day" it was common for tuners to really *struggle* to provide more than 25 dB of separation. To put things into perspective, it is very UN-common for a phono cartridge to provide more than 35 dB of separation, even today! Here's a picture of the front of an FM-1 tuner that has been converted to Stereo operation with the addition of the multiplex adapter: The FM-3 tuner was introduced in 1964 and basically took all the elements of the FM-1 (with the Stereo adapter included) and put them into a restyled unit featuring Dynaco's "Champagne Gold" face plate. It also added a new twist: By pulling on the Volume Control knob, you could activate a switch that forced the Stereo tuner into Monaural operation - VERY handy during low-signal conditions. This is a *bit* of a "simplification." There were actually two versions of the FM-3 tuner, but for all practical purposes, they were quite similar. Dynaco even sold "upgrade kits" that allowed FM-1 owners to replace the face plate and knobs with the more modern "Champagne Gold" versions. Here's a picture of an early version of the FM-3 tuner: Today, FM-3 tuners are commonly sold on eBay at rock-bottom prices. The problem is, many of these units (if they work at all) suffer from "rock bottom performance" as well. They hum, they drift and have little or no stereo separation. Why? As with most tube-type electronics, HEAT is thy enemy! After many years of faithful service, an FM-3 tuner will suffer from poor alignment, resistors that have drifted in value, bad tubes and one more "little" problem: The FM-3 tuner uses a dual "magic-eye" indicator tube that was discontinued by 1970! In fact, Dynaco sent out a letter to it's dealers and even some of the purchasers of its tuners offering to buy "any and all" EMM801's that might be available - even a quantity of ONE! Sadly, they were unable to procure enough of them to continue production and the FM-3 was quietly discontinued around 1970. So why even bother trying to restore one today? Because when properly operating, they simply sound SO good! Restoring an FM-3 tuner today is complicated by the fact that MANY of its parts are now made of "unobtainium." If you happen to own an FM-3 tuner, or are considering buying one, do yourself a favor and also buy a "parts unit" in order to have replacement parts available to properly restore and repair your existing tuner. If you are thinking of buying an eBay unit, here are some things to watch out for: Does the tuning capacitor operate smoothly with no "play" in the tuning knob? Do the plates of the tuning capacitor mesh without touching? Does it have all of its original tubes? (This is ONE time you certainly hope it does! Dynaco used two Telefunken 12AX7's in the FM-3 - needless to say, they are VERY desirable, but chances are, they were "harvested" by the eBay seller and sold for BIG bucks elsewhere!) Are all tube shields present? (Every tube except the rectifier and the tuning indicator should have a shield). Is the tuning indicator tube present and does it light up with a normal blue-green glow? Replacements ARE available, but they are expensive! (I may possibly have the largest stock of NOS Telefunken EMM801's in the WORLD - about thirty!) Does the unit pick up ANY signals and play them? If it DOES make SOME sound, when you tune it, is there a "scratchiness" to the audio when tuning? Is there ANY stereo separation at all? What about cosmetics? Does your potential "candidate" have a nice looking face plate and knobs, with all lettering intact? And here's one more tip: Do the IF transformers have a flat top, or a "sloped top?" (You want the ones with the "sloped top.") If the answers to the above questions are in the affirmative, there is "probably" no reason why you can't restore your FM-3 tuner back into the "picture of health!" In response to our "poll question" we are going to be restoring an FM-3 tuner - just to see exactly how difficult it will be. But not only that, we're going to be rebuilding TWO of them at the same time. One will feature Allen-Bradley carbon composition resistors (much like an original FM-3), while the other one will feature more modern metal-film resistors. There are reports that metal film resistors have a tendency to compromise the performance of an FM-3 tuner, and I wanted to see for myself if this is actually the case. When we're finished, we'll have at least ONE (mostly) new Dynaco FM-3 tuner! With REAL luck, we'll have TWO of them! Cross your fingers and hold on tight, this is gonna be REALLY fun!Sincerely,Bill Thomas
