Fisher MPX Adapters

Discussion in 'Fisher Forum Stickies' started by TheRed1, Dec 22, 2011.

  1. TheRed1

    TheRed1 Console Conservationist

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    After reading the thread about Stephen J's 100-T which, at some point, turned into a thread on Fisher's MPX adapters, I thought now might be a good time to start a dedicated Fisher MPX thread.

    Fisher's first MPX adapter, the MPX-10 came out in 1959 (perhaps as a 1960 model). It was designed to work with the Crosby multiplex system; then used by a handful of broadcasters who were experimenting with it at that time. It is the model Fisher recommended for use with both the 1960 Custom Electra III and the 1960 Premiere in their owner's manuals. It is a 5-tube model comprising 4-12AX7s and 1-12AU7.

    [​IMG]

    The MPX-20 came out in 1960 specifically for concealed installations. Also intended for the Crosby system reception, it was designed to fit right into the chassis of the FM-100, 100-T and 202-T. It's curious that the 101-R tuner isn't mentioned. It is a 4-tube model using 12AX7s.

    [​IMG]

    The MPX-100 was being advertised as early as May 1961 (only a month after the FCC decision) alongside such models as the TA-800, 500-S, FM-200 and the FM-50. It is a "Universal" MPX unit designed to work with any high quality, high fidelity FM receiver or tuner. The 1962 President used it conjunction with a 202-R tuner. I know I have seen an image of that control panel somewhere but I can't seem to find it. It is very impressive. The MPX-100 is a 5-tube unit consisting of 1-12AT7, 1-6AB4, 1-6AU6, 1-ECH84 and 1-12AX7.

    [​IMG]

    The MPX-200 was a 4-tube version of the MPX-100 designed for concealed installations. Despite having one less tube, it has the same specs as the 100. I don't have a firm date for its release but it was out in time for the 1962 model year.

    [​IMG]

    Fisher put out a pamphlet on FM Stereo Multiplex for the 1962 model year (copyright 1961) which goes into some detail on the subject. The following are some pertinent sections:

    In 1963 there were three different, new MPX units: MPX-60, MPX-65 and MPX-77. All were 3-tube units with the MPX-60 consisting of 2-12AT7s and 1-12AX7. Both the MPX-65 and -77 use 3-12AX7s. I only know of MPX-60 units from the high-end consoles like the President VIII, Regent and Executive VIII - though perhaps they were also used on the very high-end tuners like the R-200 (Perhaps you could check when you get a chance, Jon). The MPX-65 is quite common, occurring in the ubiquitous 400, 500-C and 800-C receivers as well as in all of the mid-line 1963 console tuners. The MPX-77 was used in the low-end console units like the Diplomat and the Philharmonic III.

    The MPX-65 and MPX-77 carried over into 1964. I'm not sure about the MPX-60. Further research is required.

    In 1965 the new 2-tube MPX-125 was being used in the mid-line consoles. The MPX-77 continued on the low-end models. I'm not sure if there was a premium MPX used in on the high-end consoles. Again, further research required.

    And I realize now that I didn't look at 1966 but I suspect that solid state MPX units would have made their appearance by this time. I doubt whether they had individual model numbers and were most likely an integrated part of the chassis. The MPX-77 or MPX-125 may have survived on the still-tube Philharmonic and the MPX-65 was certainly still available on the 400, 500-C and 800-C at this time.

    Did Fisher ever produce a separate, solid-state MPX unit? I rather doubt it.

    Further information, corrections, clarifications or questions welcome.
     
    Last edited: Dec 27, 2011
  2. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Red; Apparently by '66 Fisher may have incorporated the mpx circuit into the tuner in at least some if not all of their units. This is a 69T chassis from a 66 ambassador, that's in the CONSOLE PICTORIAL thread. BTW Annabel's R3 is #8060. She posted pics, and we missed them apparently.

    [​IMG]

    Larry
     
  3. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

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    Don't forget the oddly-named "WX" board, using two 12AT7s and one 12AX7. It seems to have been the first drop-in board, used in the "B" series receivers and some tuners. Also, the MPX-100 changed rather significantly after the first 20,000 units, and somewhat less significantly with each 10,000 made after that. Chasing down service data on the MPX-100 is a serious headache, and the Sams folder only covers the earliest model. Fortunately, the 20xxx models (which I have) and the 40xxx models (the schematic I have) are fairly similar.
     
  4. TheRed1

    TheRed1 Console Conservationist

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    Thanks, Larry. That means that in 1966 the Futura, Ambassador and the Executive all had the MPX integrated into the chassis. I checked the schematic for the '66 Custom Electra and that still used the MPX-125. That chassis was also used in the '66 Diplomat. Still not sure about the Philharmonic.

    I wonder when Wrigley posted those photos. I did email her when you got your Coronet but I didn't hear back.
     
  5. TheRed1

    TheRed1 Console Conservationist

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    Thanks, Sam. I was not familiar with Fisher "WX" MPX. I don't have either B series receiver schematics. I thought you were referring to another brand in Stephen J's thread. Good information on the MPX-100, too. I know you've been struggling with yours. I wish I could have helped but I only have the Jan. 1963 Sams which I assume is the first since it does not list any serial number range.

    I do have both the MPX-10 & MPX-20 schematics though I don't suppose anyone would be interested since there aren't any Crosby system broadcasters around as far as I know. I wonder if they can be modified to receive current MPX broadcasts.
     
  6. buglegirl

    buglegirl In The Direction Of The Singularity Subscriber

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    Sam,

    And not to hijack the thread but this is applicable as I have a MPX-100 here. What serial number is your MPX-100 ???

    Frannie
     
  7. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

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    21985B. It's very different than the pre-20xxx version described in the Sams folder. The seven-pin socket is in very poor shape on mine. I intend to replace it, along with the 68 ohm resistor between pin 7 and ground. The resistor in mine has drifted up to about 78 ohms. It might help the relay weirdness.

    If there is a regular "MPX-xx" model number for the WX board, I haven't been able to figure it out. "WX" right in the middle of the board is the only marking on the examples I've seen. On that note, I've been wondering if there would be any advantage to upgrading my 800B from the 12AT7/12AX7 WX to the all-12AX7 MPX-65, as I have the latter laying around.
     
    Last edited: Dec 22, 2011
  8. buglegirl

    buglegirl In The Direction Of The Singularity Subscriber

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    Hiya,

    Darn .. my service manual is for 40001 to 49999. Mine is 401?0 serial so its a late one.

    Frannie
     
  9. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

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    That's the same service manual I have, the circuit is pretty close to the 20xxx range. Does yours have more than the schematic, parts list and tube layout? I think my copy is incomplete.
     
  10. buglegirl

    buglegirl In The Direction Of The Singularity Subscriber

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    Hiya,

    Single one page fold out like you likely have. I have the operating instructions also but nothing in there hard core as to aligning etc which is what I think you are after.

    Frannie
     
  11. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Think about this. When Multiplex came out, the B-girls, and the C-cups were already in production (but not necessarily in the stores yet.), and a complete from the ground up re-design wasn't in the cards. They designed them to accept either version of MPX when it came out, hence the 9 or 10 pin headers on the schematics. When FISHER went Solid State, MPX was an established item for a year or two. Designing each tuner or console tuner/pre with an integral Multiplexer made sense. Making it an add on increased costs all around and I don't think Mr. Fisher or the Penny Nazi's wanted to spend $$ on extra's if they could avoid it.

    Larry
     
  12. buglegirl

    buglegirl In The Direction Of The Singularity Subscriber

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    Larry,

    Interesting terminology :)

    Frannie
     
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  13. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    That's what i get for hanging around other "Bubbleheads" all my life.
     
  14. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Got this last night from Kory(kpaxfaq). Clean but not shiny.
    MPX-100 Serial # 21784B. Replaced all the small lytics and the .1uf caps from stock. Got a couple .047's to replace and the selenium rectifier. Am actively got feelers out for a manual.

    BEFORE and After cleaning with Brasso, a toothbrush and some T-Shirt. Both jewels need reglueing. Right now I have clear tape across the back holding them in.

    [​IMG]

    [​IMG]

    [​IMG]


    WEDNESDAY 3-20-13. It's got an open secondary winding in the transformer. So gotta figure out how to deal with that one.
     

    Attached Files:

    Last edited: Mar 20, 2013
  15. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Red: The 800-C that originally was in the Executive I got from Fran, has the MPX-65 in it. The serial for that 800-C is in the Range specified for the EXECUTIVE VIII(Model 950). I'm thinking the MPX 60 was used in the 800-B in the Executve VII

    Both of my Custom Electra's and my Futura (64/65 & 65) have a MPX 125 in them.

    Larry
     
  16. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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  17. analog addict

    analog addict Glory or Death!

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    Here's another one....

    Like usual, trying to confound things a bit. My 460T/460A combo came with this one, a MPX-70 unit, which looks almost identical to the MPX-65, of which I also have an example on the shelf. BTW, the previous post/MPX-78 might be a MPX-70....:scratch2:

    I had a second of these, but it wound up with Omegaman to complete a console rebuild he was working on....:thmbsp:

    [​IMG]
     
  18. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Alan; The MPX 78 is closer to the MPX 125 which has the circuit boards and have locator slots to hold the boards in. The 70 doesn't have the slots.
     
  19. analog addict

    analog addict Glory or Death!

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    Roger that Larry. Plain as the nose on my face....:stupid:
     
  20. FauxHall

    FauxHall Super Member

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    I've got a Curtis-Mathes console (chassis 28C) with FM mono and a single RCA MPX out plug. The schematics looks like nominal voltage to the MPX is -0.1 V and the pre-amp the normal -0.2V.

    Would the stand-alone Fishers (MPX-100 or MPX-200) handle this input and deliver the right output voltage?

    My chassis has a MPX power supply plug. It supplies from 180v to 280V (from bracketing schematics - don't have the specific 28C drawing but it's probably 250V.) It also has indicator light power at, I think, 6.3V. What would one of the Fisher tethered units need?
     

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