Fisher MPX Adapters

Hello Dave. No, there is not a stereo indicator light installed but he did ask if I wanted one. I decided the only way would be to drill a small hole which I didn't want to do.
 
I recently bought several Fisher items up in the LA area and included was a 202-T with a MPX-50. The MPX-50 was a factory plug-in replacement for the FM-100, 100-T, 202-T and for the same models in a radio/phonograph combination with the Coronet model 808, Coronet II models C55 and C55A, Statesman 1010 and Statesman II model ST-70.
I will see how this factory plug-in performs once the 202-T is rebuilt. Here's the first page of the MPX-50 manual.

MPX-50.jpg
 
Last edited:
Vendo -- Hopefully you got a schematic, or at least can post an underside pic so we can see how different it is from the more traditional Fisher MPX sub-chassis. It may not be that different at all -- just in how the terminations/connections are made.

What is interesting however, is that Fisher in fact tried to retrofit a proper MPX unit for those receivers and tuners that were REALLY designed for the MPX-20. It brings up the age old questions again of how did they indicate stereo reception? How did they cause the tuning indicator to indicate optimum stereo channel tuning? Or, did they not address these things at all? Any info you can glean will be appreciated!

Dave
 
Here's photos of the MPX-50. It uses two 12AT7's and one 12AX7. One thing I noticed different than the ones I've seen is the large 20UF 250V cap on top. I'll scan the 4 page manual. No schematic but lots of information.

MPX50 2.jpg MPX50 3.jpg
 
Looking forward to the scan! From what I can see of it, this unit is an early version of Fisher's time division concept, but lacks the refinement of their later WX and MPX-65 (and other) units. It uses two single diodes for detection of the regenerated sub-carrier, as opposed to the dual ring detectors of their later units, but still functionally operates the same. Should be very interesting to get your impression of how well it performs!

Dave
 
Last edited:
For those of you who have a 59' or 60' Series 610 Consolette you can adapt it for Multiplex. The '60 Custom Electra is basically a 610 and a 560 companion in one cabinet and uses the same amp's and tuner. The C.E. tuner has been wired for MPX. Using the 60' Custom Electra Schematic, you can adapt your Consolette to accept MULTIPLEX. I did this a couple years ago and it works very well. I'm using a Sherwood a3mx converter as it's small enough to be shoehorned into the cabinet but a mpx-200 is a viable alternative. The MPX-100 will be a sit on the floor underneath deal or mounted to the back of the 610. I detailed it in this thread. http://audiokarma.org/forums/index.php?threads/610-consolette-chassis-overhaul.547187/
 
Begging your pardon guys, Larry have you gotten around to fixing that transformer issue on your 100?
 
Yeah. I had a new one made by Heyboer that summer. I used the specs from the SAMS photofact for the MPX-100, sent them my old one and asked them to incorporate the endbells from my original. Works like a charm. IIRC the cost was something like $78.00 shipped.
 
From POST #1
The MPX-100 is a 5-tube unit consisting of 1-12AT7, 1-6AB4, 1-6AU6, 1-ECH84 and 1-12AX7.

Red's quote refers ONLY to the 1st series (serials10001-19999)
The 2nd (20001-39999 serials) and 3rd series (40001-49999 serials) used the following CHANGED tube lineup. 1-12ax7, 1-6AB4, 1-6BL8 (ech80), 2-12AT7's

I've checked with numerous sources, and so far it appears that FISHER never did publish alignment instructions for any of the MPX-100 or MPX-200 Multiplexers.
 
Last edited:
Great thread and very informative.

I have a TA600 currently being restored. The manual suggest the MPX-10 as an example of the MPX unit to add so do I assume the TA600 is set up for the early Crosby system? If so, where so I start if I want to add an MPX unit? Which one do I look for?
 
The Crosby system was made defunct by the FCC Ruling in 1961, with the Zenith/GE system being the standard MPX. You can use any available mpx unit with the TA-600, as long as it's designed for the ZENITH/GE System. The MPX 10 & MPX 20 units are now relegated to nice to look at pieces that belong in museums or collections. They aren't a viable unit for use. Look for either a MPX 100 later unit (see post 52) or a mpx 200 if you want to keep it FISHER. I have a Sherwood M3ax and it works just fine with all of my tuners and receivers to get mpx. Actually it's in better tune than my MPX 100.
 
Resurrecting this old thread. Working on a MPX-100. Read that alignment instructions are not available? What are the options, if any, on alignment?

Unit I have starts off working, then in 10 minutes or so it goes crazy... relay starts chattering and audio gets whacky. Replaced all the PS electolytics and voltages all looked better but issue remained. Has original rectifier but output is good.
I pulled out 6AB4 tube for stereo beacon amp since its related to relay. Then played it for a couple of hours in Stereo Manual mode without any issues. Tube pulled tests like new so I dont think its the problem. Ordered some spares as its still most likely cause. Read that the resistor on pin 7 may cause thia but it measures at 69 ohms.
While I will try and fix this wondering if this function is really needed if you have the switch set to Stereo Manual? Seems like this function is used when in Stereo Mono Automatic... I gather switching between mono broadcasts and stereo was a thing back then... But if only interested in stereo I would think the switch would be kept on Stereo Manual? At least the stereo beacon light stays on with the tube pulled ( relay doesnt ring like a door bell). Not sure if there more to the function that I understand. Want the audio to be the best it can be but not sure if this feature impacts audio if playing just stereo.
TIA for any tips on this unit. Pretty cool piece of equipment.
 
Last edited:
Back
Top Bottom