• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

MF-300 & Remote Control Acquired

audmod01

audmod01

Super Member
I contacted the person on eBay who was selling an X-202-B and MF-300 combination with remote control and managed to persuade him to separate the tuner and remote from the X-202-B and completed a deal on it today. It should arrive by Nov 11. I was fortunate to obtain this unit complete with the hand held remote and companion receiver. Not all MF-300 units came with such complete remote control. Fisher also offered it with a wired remote control for less money. Both remotes were optional.

The real issue with all of these units is that very little documentation is available. No one seems to have the official Fisher addendum that detailed the differences between the MF-300 and the FM-200-B tuner that it is similar to. I plan to spend time documenting the MF-300 and the remote control pieces in as much detail as I can manage so that others will have some decent service information to turn to if and when their unit needs to be repaired.

The seller is going to put the companion X-202-B back up for sale soon and it appears to be a really nice condition unit also.
MF-300- web 01.jpg MF-300- web 02.jpg
Joe
 
Last edited:
Register to hide this ad
Wow! Joe -- That is great! What a sharp looking unit, too! I would imagine that the difference in actual tuner circuitry are quite small -- that the only real difference is in the automated control circuitry.........?

Please keep us posted!

Dave
 
Dave and Ron;

Thanks. Yes, as I remember from working on one years ago, the MF-300 is identical with the FM-200-B except for the added parts that implement the electric tuning. I seem to remember that there is an extra tube, maybe two, that handle the switching of the drive motor for tuning and volume level change. However, it has been about 51 years since I touched one. The remote control is an ultrasonic type and would bear some similarities to ones that RCA used with some of their tube type color TV sets. There are some common problems that these tend to develop over the years. I believe I can manage to get this one working properly again. The FM tuning is working fine manually and so does using the front up or down tuning buttons according to the seller.

I am looking forward to documenting this unit for posterity. These units deserve to be restored and be fully functional. I hope to accomplish that and will share any documentation with members here if I manage to complete the task. I will start with some good pictures of the chassis top and bottom etc. Since I already have the FM-200-B manual versions on my computer, I can easily pull up the pages I will need to start documenting the MF-300. I am hoping that all of the significant special parts associated with the electric tuning motor operation will have Fisher part numbers on them. Any vendor supplier ID numbers will also be documented.

The remote hand units are likely unique to just these Fisher models. Their concept is simple - an on-board ultrasonic oscillator with several capacitor values to switch into the oscillator circuit and change the output frequency. On the receive end there will be coils that will respond to the specific ultrasonic frequency sent by the hand unit and activate a relay to energize the drive motor(s). I am not sure if there is a separate motor to turn the output level controls or if there is a single concentric control on the remote receiver chassis to control audio level. The unit I worked on years ago at the dealer was a unit that did not have the optional remote control. This is going to be a real learning experience.

I had a conversation with Vendo81, as he has one of these, and learned that his unit's remote control is not working. The battery for the hand unit goes bad and there may not be a direct substitute any more. Some research to that end is needed. He was helpful in suggesting an average value for the units and I was successful in getting this system within the value range we discussed. It pretty well has my part of our monthly budget maxed out, but I think it will be worth it to get the information available to others who own these units.

Joe
 
Joe; Magnavox had an optional "ultrasonic" remote on their TOTL consoles back around '64 when the Astro-Sonic's came out, IIRC. Opened up it consisted of two bellows below the buttons pushing air thru 2 "whistles with frequencies of approx 22kHz and 24kHz. One turned the unit on and off and the other varied the volume via a 4 step wheel connected to a solenoid affair.

Larry
 
Larry;

Yes there were various methods of emitting the desired ultrasonic signal. Zenith had their tuning rod design which incorporated spring loaded strikers to hit the appropriate tuning rod. I could be wrong about the hand unit, but I think I am correct because of the presence of the battery in it. There is something to be said for mechanical means of creating the needed signal. They tend to be very long lasting with few modes of failure. RCA also had stepper volume change remote units as did Zenith on some of their televisions. One downside of these ultrasonic designs was that they sometimes responded to pocket change or keys being rattled. RCA incorporated a delay into some of their later ultrasonic designs in an attempt to stop that issue, but it was only partially successful. Not long after that approach they changed to the infrared remote hand units which eliminated that issue. Back in the late 1930s and early 1940s Philco had some RF remote controls for their radios that used low frequencies below the AM broadcast band and called it their "Mystery Control" and it used a stepper control for volume and selected from various AM preset station buttons. The remote chair unit had one tube inside along with the needed batteries for filament and B+ and a telephone type dial to create the necessary output pulses in the RF signal.

Lots of interesting approaches have been used over the years. Fisher's approach deserves preservation.

Joe
 
Philco introduced Mystery Control in June 1938 which was the time their new 1939 models were introduced. They tried to keep the system under wraps as much as they could, even claiming in advertisements that it was "not a radio beam" when in fact it was. Radios using Mystery Control were big and expensive, and Philco gradually pushed it less and less unitl it disappeared after the 1942 season and that year's only model with what by then was being called "wireless remote control", the 42-1016.
 
I thought of contacting him to see if he'd separate, nice grab. I've been holding out for the MF-320... might be a while.
 
Matt;
What features does the MF-320 have? I was not aware of it.

Ah, I just looked it up it is the MF-300 with the RK-20 included which makes my unit similar except I suppose the MF-320 has the remote built in instead of separate pieces?

Joe
 
Last edited:
That's it, not really different from a feature perspective - just that the 300 and 20 share a common face plate, and extra wide wood cabinet.
 
That's it. I have a Fisher catalog from about 64 or 65 that has an entry for it. Never seen one for sale.
 
Joe,

I'll be very interested in your progress. I have the MF-300, and I have the wireless remote receiver, but don't have either of the remotes. The tuner works, but its impossible to tell if the wireless remote receiver works or if the auto-tuning feature works when you don't have a remote. I haven't come up with any alternative since I had no idea what specifications to shoot for.

Good luck on your endeavor.
 
Hammr7;

I think it would be fairly easy to make an RK-10 wired remote control. Once I get the unit on hand I can check the interconnect cable socket on the back of the unit and hopefully figure out which contacts have to make and break in the remote unit to tune up or down and report that information back here. There are some small plastic project boxes that could be used along with some momentary contact switches to make one. These are interesting units.

Joe
 
A couple of good news items today: I have an update for delivery of the tuner from UPS and it should arrive this morning. I posted a query and comments about this tuner on the FM Tuners Group of Yahoo late yesterday. I had a response from a member there who has a copy of the owner's manual and the service information for the MF-300 that he is going to send me. I sent him my postal address so I hope to receive that soon. I will share the information as soon as I can.

Joe
 
MF-300 & RK-20 have arrived! I could not resist taking some pictures of the RK-20 and its hand unit. Here they are:
RK-20 web 01.jpg RK-20 web 02.jpg RK-20 web 03.jpg RK-20 web 04.jpg RK-20 web 05.jpg RK-20 web 06.jpg RK-20 web 07.jpg
Both the receiver and hand unit are transistorized as I thought. The volume control is fully adjustable just like a normal volume control. There is a 117VAC electric motor attached to the rear of the volume control along with an associated gear train. This looks exactly like what RCA used to use in their color TV sets of the same era except for voltage rating of the drive motor. There are at least 3 relays hidden under some other components in the first picture. The hand unit is transistorized and used a Mallory H-163 a 4.2V battery. There is an oscillator on board which is activated by the two push-buttons on the front.

The source from the FM Tuners Group on Yahoo said that he does not have the documentation on the RK-20, just on the basic MF-300, so this will still be a challenge to restore and document. I see lots of electrolytic capacitors that may have gone bad over the years.

I have not looked at the MF-300 tuner just yet other than to see that it arrived in good shape with no broken or bent parts. The knobs were removed and packed in bubble wrap. There is an R-200 owner's manual with the unit. Everything was well packed with energy absorbing resilient plastic foam pads of the rather firm type, so everything was well protected. I will try to get some pictures tomorrow of the tuner itself.

Joe
 
Glad to see the progress! I'll be following this thread, with hopes you unravell all the secrets of the RK-20 compnents.
 
You must log in or register to reply here.
Back
Top Bottom