Fisher FM-50 versus FM-100, any significant difference?

little-al

Active Member
I picked up an FM-50(mono) the other day for $10 plus shipping, bringing the total investment to around $25, which I thought was a pretty good deal as the unit is in remarkably good shape all around. The only thing it is missing is the wooden cabinet.

BTW, does anyone know offhand which model wooden cabinet fits the FM-50?


I've also run across an FM-100(not a b or c, just FM-100) for just a little more, and it also looks like a nice unit too.

But I'm curious, other than the option on the FM-100 to install the on-board multiplex unit, which this one does not have, is the FM-100 any better of an FM tuner than the FM-50 for monaural applications?

Thanks,
Al
 
I have a FM-100 that has a MPX unit installed. It sounded very good running in mono mode but sounds outstanding with the stereo multiplex.

I don't have a FM-50 but do have a FM-50-B. It is also a really nice little tuner. I prefer the FM-100 a bit over the FM-50. The 100 is a bit more sensitive and sounds just a touch cleaner with larger soundstage.

I have my FM-100 mounted in an original metal Fisher cabinet. The 50 and 100 series tuners will also fit in the Fisher wooden cabinets that house the Fisher 100, 101, 200 series amplifiers. I placed my FM-50-B in my X-101-Bs wood cabinet for a test fit. It's a nice match but the mounting holes are not exact. Could just be my cabinet, who knows...

Great deal you got on the tuner.
 
Sorry to revive an ancient thread (my own), but ran across an interesting detail while doing some reading on Fisher's "Golden Cascode" front end that might shed a little light on how the FM-50 might perform in comparison to other Fisher tuners and receivers.

If one reads Alan K's (aka WopOnTour) document "In Search of the Golden Cascode (Debunking The Myth of the Golden Synchrode?)", on page 14 he illuminates that the Fisher 500B actually does not have a cascode tuner, and instead has a more common 2 IF and 2 limiter stages, but is considered a very fine FM tuner. The 800B was very similar.

Looking at the FM-50 service manual, the FM-50 too appears to have a very similar (the same?) circuit and 2 IF and 2 limiter stages using the same tubes as the 500B and 800B (800B has one less limiter) :)

I'm not making any judgement of the 500B/800B, but found it interesting that Fisher's bottom-of-the-line FM-50 tuner had at its core the same quality circuit design as Fisher's top-of-the-line receiver tuner sections. I have no idea if the quality of the components, switches, tuning capacitor, etc.. were better on the higher end models, but I think it is pretty neat that the little FM-50 was no cheap compromise and seems like it probably focused on doing the basics well.

And as an aside that also makes the FM-50 special is the built-in volume pre-amp via a 12AX7 (record level out knob) on the front panel of the FM-50 ... even thought that is not what it was meant for ;) It pairs up with my 30-A amp surprisingly well as a simple volume control :thumbsup: That front panel knob disappeared with the FM-50b and beyond.
 
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My FM-50 plays very well for a MONO Tuner. IIRC the FM-50 was a 59 or 60 model. FISHER used the same components all along it's tuner lines, varying the performance parameters by the # of RF & IF sections and limiters. Fisher was DOING this long before Zenith's marketing came up with ,......"The quality goes in before the name goes on"......insinuating that if it didn't meet their "Hi Standards" it got discarded or rebuilt until it did.

You have to remember that the FM-50 and the 800B were built in that time where FM STEREO was in flux. Between 1958 and 1962 Tuners were built to accomodate 2 or 3 different arrangements to create FM Stereo. Some radio's as early as the lower mid 50's had a multiplex out RCA jack.
FM-FM (2 tuners required) Each channel was played by a different station.
FM-AM (2 Tuners required) One Channel FM, the other AM (otherwise same as FM-FM).
Multiplex of 2 different parameters in limited markets for testing by FCC. Multiplex as we know it didn't get approved until spring 1961. You had the crosby system (which was actually superior in most conditions except for it's FM carrier which negated the SCA signal that muzak, etc. used) and the GE-Zenith System (AM Carrier and able to use the SCA signals). The FM broadcasters were making pittance on FM broadcasting and most of their income was from SCA contracts with Stores.

As such outboard Multiplexers were available, and FISHER was actually betting on the Crosby system. The 202-T being a very short lived tuner from FISHER was designed around using a built in multiplexer of the Crosby type. When the GE/Zenith format was chosen by the FCC, FISHER had designs with internal Multiplexers ready to go and production of the 500b/800b started almost immediately. Same with the pure tuners.
 
I realized I don't think I ever posted a photo of my $25 FM-50 post renovation. It was in great shape cosmetically, although benefited from the standard cleaning and waxing.

Standard re-capping and parts replacement commensurate with my amateur skill-set worked out great.

I then had a local frame shop make a frame for the face plate versus hiding the chassis within a wooden cabinet, as I really like to see all the ectro-mechanical bits in action :thumbsup:

I find that this little tuner really is great due to its simplicity and sounds great.


Fisher-FM-50-Sept-2020-004.jpg
 
I was under the impression that the cascode was describing the RF amplifier section, not anything else in the circuit. Don't have a schematic in front of me so no idea if these actually used it or not but a cascode looks kind-of like a cathode follower. If the antenna signal feeds into the grid of a triode and the cathode of that triode connects to the plate of another one, thats a cascode amp. If its the more conventional in on the grid, out on the plate, and the cathode goes to ground somehow its just a triode.
 
If I may -

This thread caught my eye, since I own both an FM-50 and an FM-100.

While looking for something else a little while ago, I stumbled across a Fisher brochure which lists and gives details for the FM-50, FM-200, 100-R & 202-R. (The FM-100 is not mentioned.) I noticed in this brochure that Fisher did not call the front end of the FM-50 "Golden Cascode" - they referred to it as "TrioMatic."

If anyone wants, I can scan and post a portion of the brochure describing the FM-50 although it does not go into detail about the "TrioMatic" front end.

My FM-100 is in very nice condition and includes the optional metal cabinet. My FM-50 was originally purchased for parts as its front panel is not in the best of shape. But then I sort of felt sorry for it and attempted a restoration, which was successful. You can read about that here:
https://ronsradios.com/2020/08/18/the-fisher-fm-50-tuner/

I also own a 100-R and a 202-R. The 100-R uses a now-unobtainium 6G-E12 indicator tube, and mine is quite dim. Both of these tuners also have their original metal cabinets.
 
If anyone wants, I can scan and post a portion of the brochure describing the FM-50 although it does not go into detail about the "TrioMatic" front end.

Thanks, that aligns (pun intended ;) ) with what I observed looking at the service manual's diagram, as I don't think the FM-50 has the cascode (golden or otherwise).

But yes please do scan that brochure and add it to this thread for anyone looking for more information on the FM-50.

There doesn't seem to be a whole lot of information out there, especially owner contributed, about the FM-50 which I assume is because it was the bottom of the line and filled that short gap of time between the transition from monaural to stereo tuners. So I bet Fisher didn't sell a ton of them. But as I've said, I really like this little tuner for it's simplicity and size, and it's definitely not built cheaply and works well.

Fantastic write-up on your blog about your FM-50 restoration :thumbsup:

The only thing that I really didn't do with my restoration (I think, I may have to go look :rolleyes:) that comes to mind is to add that resistor to the new silicon rectifier. I've recently seen that mentioned in a few restoration threads, but don't recall seeing that mentioned about 8 years ago when I restored the FM-50. Is the slightly higher voltage from the new rectifier a real issue, or just a best practice to address?


Thanks again!
 
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Hi,

Info on the FM-50 from the brochure (click the image to enlarge):

FM50_ad.jpg


You can download the entire 4-page brochure by clicking HERE (LARGE FILE - ZIPPED PDF, you will have to unzip to view - 68 MB).

The brochure has a copyright date of 1961 on the back. I would assume the FM-100 was out of production by then since it is not mentioned in this brochure.

Thank you Al, glad you enjoyed reading the account of my FM-50 restore. While it was pretty simple to work on, it was definitely not made cheaply - its performance attests to that fact.

I consider the higher B+ a real issue, especially with today's higher line voltages, and I believe the dropping resistor is therefore a necessity (not to mention the higher efficiency of silicon rectifiers resulting in higher B+ voltage).
 
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That's a fascinating brochure, and what's really interesting is that all the specs for the FM-50 seem to be better or in a few cases equal than the FM-100-R :cool:

Of course again, the FM-50 is monaural (has MPX out though) and FM only as compared to the FM-100-R, but still... I knew this was a good little tuner :smoke:


1961-1962-Fisher-Tuner-Brochure-Specifications-Page.JPG
 
Hey Al,

Thanks for the kind comment on my blog site regarding the FM-50. I appreciate it.

I considered using the type of bridge rectifier that you used. I opted for the overkill bridge that I used simply to gain those nice solder terminals.

I see you also replaced that AC line capacitor, which a friend of mine calls "the death cap". Good job.

Bear in mind that without a MPX decoder, the 100-R is also mono FM. Ditto the 202-R and FM-200.

I've considered trying to adapt a WX (or modified MPX-65) MPX decoder to the FM-100. Not a priority though. Such a project could be quite interesting indeed. The FM-100 was designed for the Crosby MPX system (see Larry's post #4 above), which ultimately was not adopted by the FCC. The GE-Zenith system is what was adopted in 1961, and which we still use today.
 
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Yep, when I first received the unit, it had notable voltage on the chassis :confused:

Should I add that 100 ohm, 5 watt resistor to the B+ output of my rectifier as well?
 
dug up the FM-50 schematic. Definitely not a cascode. Looks like its running grounded grid mode, input to the cathode of the ECC85. Grid of the ECC85 ends up at AC ground via C3. Not going to do the math but .001uf at ~100mhz is pretty low impedance.


http://www.fisherconsoles.com/non console manuals/fisher fm50 10001 19999 sm.pdf

Interestingly my TA-600 has a cascode circuit. Never honestly looked that close at it before. I wonder if the cascode front end is more selective. Quick look at a few schematics makes me think the RF amp in the non-cascode versions is un-tuned on the input. The one on my 600 at least does tune the input circuit. Don't know if this is true for all models though.
 
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