Fisher MPX Adapters

TheRed1

Console Conservationist
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.

MPX-10.jpg


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.

FisherMPX-20-1.jpg


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.

MPX-100.jpg


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.

FisherMPX-200.jpg


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:

If your stereophonic high fidelity system does not include an FM tuner, the best method of adding multiplex would be to purchase an FM-Stereo-Multiplex tuner, with the multiplex circuits fully integrated in the tuner design. This method is less costly than purchasing a separate tuner and adapter, and is more compact. There are three new integrated FM-Stereo-Mulitplex tuners in the Fisher group of high quality high fidelity components. These are the FM-50-B, FM-100-B and FM-200-B. Each unit combines complete multiplex facilities with the highly praised characteristics of its pre-multiplex version (Models FM-50, FM-100 and FM-200). The FM-100-B and FM-200-B include the Fisher STEREO BEACON and Automatic Switching System, while the FM-50-B has another new Fisher development - STEREO BEAM. This remarkable circuit performs in the same manner as STEREO BEACON, it signals the presence of a multiplex program. In this design, however, it is the FM Tuning Indicator that shows the presence of a multiplex program.

Those who do not own a stereophonic high fidelity installation and want to enjoy the pleasures of FM-Stereo-Multiplex can make a completely new start. The most convenient and least costly plan is to purchase an FM-Stereo-Multiplex Receiver - with everything you need on one, easy-to-install chassis. Such receivers include FM (or FM-AM) tuners, multiplex circuits, Preamplifiers, Audio Control Centers and Stereo Power Amplifiers. Simply add two speaker systems and a turntable for a complete high fidelity stereo system. If this type of stereophonic high fidelity system appeals to you, the Fisher 500-B FM-Multiplex Receiver, or the 800-B FM-AM Multiplex Receiver, will meet your most exacting requirements.

Fully anticipating the advent of FM-Stereo-Multiplex, Fisher engineers have included facilities for multiplex conversion in all Fisher stereophonic radio-phonographs. Owners of the Fisher Philharmonic II (P-25), Custom Electra V (E-46), Futura III (F-50), and Ambassador IV (A-60) can easily convert to multiplex by adding the Fisher MPX-70 adaptor. The Executive VII (Model 990) and President VII (Model 7000) are already equipped to receive multiplex stereophonically. All other models can be converted for stereophonic reception of FM-Stereo-Multiplex by the addition of the MPX-100 Universal, the MPX-200, and for some, the MPX-50. Inquire from your Fisher dealer which model to get.

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.
 
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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.

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Larry
 
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.
 
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.
 
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.
 
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
 
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.
 
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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
 
Hiya,

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

Frannie

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.
 
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
 
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.

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
 
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.

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

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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.



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
 
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:

 
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.
 
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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