The Japanese Type 94-5 Wireless Sets

The Japanese Type 94-5 Wireless Sets

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The Type 94-5 was considered the Company and Battalion level sets. The Battalion signal company would send a radio team down to each company to provide communication back to the battalion. The battalion also used these sets to stay in touch with regimental headquarters. The set was transported in two chests. I have a very poor picture and description of the No 2 chest.. The No 1 Chest held the transmitter, the receiver and the accessory bag. It is assumed the No 2 chest held the generator and everything else.

This station is made up of a receiver, a transmitter, a hand cranked generator and related accessories. The transmitter is a small, one tube set, powered by a hand cranked generator.

A detailed analysis of the set was done by Ken Lakin in Electric Radio Magazine. Ken got the set on the air using a US type 19 tube, which has a 1.5 volt filament rather than the 6 volt UZ 12 C tube, which is a very rare tube. He also used a power supply

as he did not have a hand cranked generator.

Japanese Type 94-5

Type 94-5 Display

Even with the generator, I doubt he could have talked his wife into cranking it! This also explains why most GI's did not bother to bring home the generators, a major factor in the high cost of finding a generator today!

Ken also got a Type 94 - 5 receiver that was out of the case and in very poor condition. He did a marvellous job of restoring the set, probably more work than anyone else would consider doing. This set was also described in an article in Electric Radio. I can not say very much more than Ken about the technical aspects of the set. This set was one of the sets that was the subject of a technical bulletin in WW II as it was felt that these sets could be used by U.S./ Allied personnel to supplement their own communication systems.

Type 94-5 Transmitter Internal View

Type 94-5 Transmitter Internal View

The transmitter is a 5 watt transmitter and the range is adequate for it's intended purpose. For HAM radio use, it will reach out but does not have the range the more power full sets have. By comparison, a Citizens Band radio, which is limited to 5 watts has a range of about 5 miles in a mobile unit, more when operating a base station. With a good antenna system, the range is increased considerably.

Seldom does one find these sets together. You may be lucky and find the receiver and then go looking for the transmitter or as was the case with Ken Lakin, find the transmitter first and then go looking for the receiver. These sets came in metal cases which had leather side flaps and top and bottom flaps. In many cases, the GI who brought the set home, cut the leather flaps off as it makes the set easier to use and easier to display on a shelf., however it cuts down the value considerably.

Type 94-5 Open Chest

The first set I got had the leather flaps cut off. After that, I picked up sets with leather flaps. I was very fortunate to get both receiver and transmitter and accessory case in the transport chest along with numerous accessories. Interestingly enough both transmitter and receiver had matching serial numbers, a rare find. Both transmitters and receivers had carrying slings and were also fitted with hooks for a back pack. Shortly after this set came in, another transport chest was located but the inner compartment dividers were removed.

Japanese Type 94-5 Radio Set What is the set Worth:

In 30 years of collecting military relics, I had never seen any Japanese radios. In 1987 I found one Type 94-5 receiver. Then in 1992 these sets began to show up all over. Military shows, Radio Magazines and the Inter net. As a result, I have established the following guide lines for establishing a fair value for these sets

Type 94-5 Receiver in near mint condition $350.00 - $600.00

Less the leather flaps, deduct -$ 50.00

Less operational tubes at $20.00 per tube -$ 60.00

Damaged Case:

Visible damage, deduct - $ 30.00 per item

This includes missing hinges, data plates, extra holes

Invisible Damage - $ 20.00 per item

This includes missing battery cables, missing battery plug

Damaged Receiver:

Missing a control dial or knob -$ 30.00

Missing a major component, capacitor, rheostat ,panel -$40 to -$50 per item

Missing a major, non panel component such as transformers -$20.00 per item.

Missing a minor component, resistor, capacitor -$5 to -$10 per item.

Receiver only, complete, no case $ 75.00

Type 94-5 Transmitter in near mint condition $300.00+

With original UZ 12 C tube with good filament, add $ 82.00

Less Leather Flaps, deduct - $ 50.00

Visible and invisible damage, same as for the receiver. It should be noted that these transmitters were rarely used by HAMs and seldom show any signs of damage. They are usually missing the original tube and seldom have any crystals. The transmitters and crystals are relatively rare items, there being about one transmitter for every three receivers.

Type 94-5 Complete

Accessories for the Type 94-5 set

No 1 Transport chest, complete with all shelves, holders and parts list $200.00.

Missing the shelves $125.00.

No 2 Transport Chest, holds the Generator and other items $250.00.

F19 Hand cranked generator (very rare item) $325 to $500.

Generator Power cable (Another rare item) $50 to $75.

Headset / throat mike, complete, operational, with plug $150.00.

Missing the mike or the plug $ 25.00.Most of these have deteriorated cables, decomposed rubber boots. Mike rubber straps are badly stretched. Headphones usually do not register on continuity checks so test with a 9 volt battery.

Click On Picture For Exploded View Of Items

Accessory bag ( A rare item) $75.00.

Key, with base, cable and plug $75.00-$150.00.

Transfer cable, receiver to transmitter, with both 5 pin plugs $50.00.

Receiver bench test power cable, usually found missing one end $25.00.

Antenna, antenna lead in, counterpoise wire.

The antenna and counterpoise wires and reels are rare items, get good documentation on these items as any copper wire can be claimed as an original and stuck on bamboo insulators. $30.00 per item if documented. I have available reproduction antenna reels and wire for all sets.

Seldom does one encounter the accessories and when found may be cheaper because the owner does not know what they are.

In June 2000 a complete station, both chests, all accessories, transmitter, receiver and generator sold for over $5000.00 on the eBay auction. This was a rare find which accounts for the high dollar value.

THE TM

Before starting any work on the Type 94-5 sets, you should have a copy of the U.S. Army TM on the set. This is TB Sig E-19. I can let you have a copy of the U.S. Army TB on the Type 94-5 set for the cost of the photo copies.

Number 1 Chest

Number 2 Chest

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THE TRANSPORT CHESTS

There are two chests that this set comes in, the # 1 holds the receiver, transmitter and accessories bag, which has the key and a headset/mike combination and the antenna and counterpoise and the #2 chest holds the generator and everything else.

Click On Picture For Exploded View of Items

THE ACCESSORY BAG

One of the items in the Number 1 chest was the accessory bag, shown above. It contained the key, a throatmike/headset unit, the interconnect cable and the bench test cable.

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THE GENERATOR

The generator, has a side plate which is worn by the Number 2 man on the radio team. It is worn as a sort of breast plate and the generator flops down and the #2 man who is wearing the generator can crank it while standing there. The side plate is not necessary for operation of the generator. Inside the generator there is supposed to be an arm which has a voltmeter with marking of 0 -7+ volts. Well marked at 6 volts so you can determine if you are cranking fast enough. If the arm and meter are missing the generator will still work if the generator puts out the proper voltages. The schematic for the generator is on a data plate on the generator and also in the manual. Basically 6 volts and 150 volts DC. To get to the insides of the generator, loosen all the screws holding down the cover and then the cover flips back exposing the actual generator.

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THE RECEIVER

As to operating the receiver: I have had about 8 of them and only one works! Two were close to working. Usually the interstage transformers are bad and must be rewound. Then the capacitors usually are bad and must be replaced. This requires a major overhaul. Almost complete

disassembly of the set. You have to take off most of the top side components to get to the bracket that holds the capacitors in place. Then take out the capacitors, open them up, melt out the tar insides, replace them with orange drop capacitors and reinstall them. If your set has bad interstage transformers, Gary Brown does an excellent job of rewinding them but at $85.00 per transformer, with three of them, it gets expensive. The filament rheostat is a simple rehostat but the regeneration control is a very complex item to rebuild. See the article that Ken Lakin wrote in Electric Radio back in the late 1990s.

US tubes can be substituted for the Japanese tubes but you have to have a Japanese tube base to do this. And even dead Japanese tubes are valuable items and only if you find a broken tube is it worth making the modifications. Ken Lakin made several of them for his sets and he made me one.

If you are lucky and the headset works, great but if not, you can make an adapter from two banana plugs and phone jack and use any high impedance headset.

THE ANTENNAS

There are two antennas with this set or more properly an antenna and counterpoise wires. These are wrapped up on an antenna retriever. I had a bunch of reproduction wooden retrievers made up and I can sell you two of them.

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THE TRANSMITTER

Unless your wife or girlfriend is a Sumo wrestler, I would suggest that you construct an AC mains power supply. I built a power supply for the transmitter. The basic schematic was from the AES antique battery eliminator kit. I can send you the schematic or you can build your own version or use whatever you have already for a power supply. The AES kit sells for about $50.00 and you can build what you need for somewhat less. Contact AES and get the power transformer. The other components can be gotten from any Radio Shack store. The receiver tubes are 1.5 volt filament tubes. The transmitter uses a UZ 12 C tube, if you can find one, which sells for about $82.00 and is a 6 volt filament or you can use a Type 19 tube which costs about $4.50. It is a 1.5 volt filament so the power supply can be used to power both the receiver and the transmitter.

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Japanese Crystals

Japanese crystals are rare items but I made a modification out of a wooden block, with two metal side plates and a socket for the standard FT 243 crystals.

Jim Karlow wrote that he put the transmitter on the bench and attached a voltage and current regulated filiment supply set at 6 volts @ 300 ma and a variable high voltage power supply connected to the 150 volt input. Antenna was connected through a 50pf cap into a bird dummy load with scope and frequency counter tap. I also turned on an HP spectrum analyzer which I had connected to a whip antenna.

The UZ-12C had filiment continuity, so I applied filiment voltage and turned the switch to transmit. The tube heated. I preset the transmitter for about 3880 KHz and set the band switch and load control. I then began slowly turning up the HV power supply, starting from zero, actuating the key and monitoring the current draw. at about 75 volts, the transmitter started producing carrier (I could see this on the scope and the spectrum analyzer), then I eased the B+ up to about 125 volts. I did not have a crystal for it so I was running off of the VFO. I did see the key clicks(incidental RF bursts, with the VFO when the key was actuated on some of the CW. I'm going to take a crystal and put the transmitter on 3885 KHz later this morning. Amazing that it still works after 60 years. I doubt this unit has been actuated since the last time it was used by a Japanese radio operator in the Phillipines. How much movement should you get from the meter ? I don't believe that I saw any movement, but then again I did not have the specified antenna on the radios.

The interconnect cable has 5 wires and connects the headset/throat mike (3 lines) on the receiver to the transmitter and also connects the antenna and counterpoise (2 lines) from transmitter to receiver and moves them back and forth, as you operate the Transmit/Receive switch. These turn up now and then but usually as part of some other deal. You can use banana plugs for this. The cloth covered 8 wire cable from AES is very close in appearance to the original Japanese cable and if you are really ambitious, you can make wooden plug holders and it will almost look like the original.

Any standard key can be used if you do not have a Japanese key. The Japanese key for this set has two pins, again banana plugs can be used. The Japanese key with the 1/4" plug is for the Type 94-3 sets and several other sets.

I have not had any of my transmitters working yet but there is not that much to them to go bad.

Both the transmitter and receiver have or should have the calibration chart and the schematic and parts list but these are real small and you may need to get them photocopied and blown up several hundred times. The schematic in the U.S. Army manual will suffice.

CHECKING OUT THE TYPE 94-5 RECEIVER

The first step in checking out this set is to remove the tubes and check the filaments for continuity. If they are good, set them aside for later use and proceed to the next step.

Connect a 1.5 volt battery to the terminals at the rear of the set being careful to observe the correct polarity. Now begin checking to make certain the power is actually getting to the tube sockets. One line goes directly to the tube socket and the other line goes through the On/Off switch to the filament rehostat and then to the tube sockets. Rotate the filament rehostat and observe the readings on a volt meter. This control acts like a volume control but in actual use, the operators usually ran the set wide open.

The next step is to check the interstage transformers. If you have sensitive test equipment, you know what to do. If not, a simple volt-ohm meter can be used. I set it to 30 volts and use a 12 volt lantern battery. Check each winding for continuity. If all three interstage transformers are good, you can continue checking out the set. If any of the transformers are bad, then you will have to get it out and get it rewound.

If you go to the trouble to remove the transformers, then you might as well remove the capacitors and then replace all the capacitors with modern orange drop capacitors. Assuming that your set had good interstage transformers, the next step is to connect a B battery of 90 volts and replace the tubes. Connect the antenna and counterpoise wires and a headset. Make certain the On/Off switch is in the Off position while installing tubes and batteries. Turn the On/Off switch to the on position and allow the tubes to warm up. The set should work or at least you should get sound in the headphones. If you get a buzzing sound, which some call “motorboating” the capacitors are bad and must be replaced. Again, if you are replacing one capacitor, you might as well replace all of them. In the event that it still does not work, then you will have to do some more detailed trouble shooting. Get out the schematic and go to work.

Type 94-5 Schematic Tech Manual Pg 16 & 17 Tech Manual Pg 18 & 19 Calibrationn Charts

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JAPANESE SCHEMATICS

All parts on Japanese radio sets have a number which corresponds to the parts list and the schematic. On receivers, part number 1 is usually the antenna connector and increase with the last number being the headset connector. On transmitters, the system is reversed with the lowest number being either the key or the power connector and the highest number is the antenna terminal. In addition, the schematic as well as the wires are usually color coded with a red wire being part of the B + line and black wires used for all other wires.

Ken Lakins Complete Restoration of 94-5 Unit

Ken's first effort on restoration of Japanese radios was a Type 94-5 transmitter. He did an article on it for the May 1994 issue of "Electric Radio" magazine. His next project was the companion receiver which he got through an advertisement. The set was, as he put it, severely cosmetically challenged. In checking out the set electrically he found leaky capacitors that had to be replaced. This was not an easy task as they were held in place by metal straps with countersunk screws which could only be gotten to by removing other components. In short, he completely disassembled the set, taking many pictures of each component, wire, connection so he could put it back together. Once disassembled, he bead blasted the chassis and the connection tabs on many of the components. Then he electroplated the connection tabs. Super glue was used to fix the coil windings to the form, the main tuning capacitor was taken apart and cleaned by hand. Transformers which had open or shorted windings were rewound and the regeneration control was re built. This was a difficult task due to it's construction. Metal can capacitors were heated and the contents removed and replaced by modern orange drop capacitors and re inserted in the original cans. The set was then reassembled much as you would build a kit radio.

The pictures below show the set as he got it, with all the parts removed and stored in plastic bins and the finished set.

Before During After

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Checking the filament circuit

Bypass the filament rheostat with a jumper. When checking the filament voltage be sure the input stays at 1.4 Volts or so. Since all filaments are in parallel, you could also use jumper wires to connect directly from the filament supply to one of the tube's filament pins. That will bypass both the rheostat and ON/OFF switch. Total filament current drain will be around 200mA.

The A+ line goes to the upper contacts on the lever switch. B+ goes to the lower contacts and then to the toggle switch, which I assume is the standby swtich.

The A - line goes to the filament rheostat. It would then seem that the by pass would be in the A - line and the On/off switch would still function. After all efforts to get one of the Type 94-5 set going failed, I decided to get out one of my other sets. I did all the checks, got 1.5 volts at all filaments.

Checking the B+ circuits and interstage transformers

After checking the filament circuits, I checked the B+ circuit and I got 91.3 on UF 134 plate, 61.2 on the UF 109 plate and 91.1 on the UZ 133. All original Japanese tubes had good filaments so with much trepidation, I applied power and was almost blasted out by the sound in the headphones so I conclude the set will work, as is.

1:3.5 is the transformer turns ratio. These are high impedance transformers with an impedance ratio of 1:12 (3.5 squared) and are more likely 2000 to 24000 Ohms etc. I measured the output impedance (to the headphones) as around 8000 Ohms, so the primary side would be running about 100K. AES has similar "inter stage" or "driver" transformers.

The above schematic diagram has had all the circuits other than the B+ and B - circuits removed. It will be seen that the B + line feeds through the three interstage transformers. Removing all the tubes, connect 90 volts to the B voltage terminals. Using a volt meter check the voltage between B - and each tube plate.

Tube No 43, the UZ 133 Plate No. 2 should have 80 to 90 volts. If it does not, then audio output transformer No 47 has a bad winding. If there is no voltage on Plate No. 1, then transformer No. 40 has a bad winding.

Plate voltage for tube No. 34, the UF 109 A passes throught the regeneration control, part No. 36, interstage transformer No. 35, through the coils, No 23,25,27, and/or 29 and then to the plate. Voltage on the plate should be between 10 volts and 90 volts, depending on the setting of the regeneration control. If there is no voltage, the problem may be with the transformer. The terminals on the transformer are on the bottom (as viewed from the underside ) and are difficult to get to. Use a test probe with a long tip and measure the voltage at both terminals. One will read 90 volts, The other should also read 90 volts. If there is no voltage at one of the terminals, the problem is the transformer. If 90 volt readings are obtained at both points, the problem is probably with the regeneration control. Assuming a good transformer, check the voltage at the regeneration control. One of the end terminals should read 90 volts. If not, there is a break in the wire line. If you get 90 volts try running a jumper to the center terminal and re check the voltage at the tube socket. If this does not produce a 90 volt reading, begin checking the coils, No 23, 25, 27, and/or 29. Coils seldom go bad but this is a possibility. If one of the coils has a break, it should be an easy matter to repair it, or at least easier than repairing the transformer.

Tube No. 16, the UF 134 derives B + voltage through the coils No. 22, 24, 26, 28 and should read 90 volts. If there is no reading, the problem is probably in one of the coils. If all four tube plates have close to 90 volts on the plates, you are ready for the next step.

Make certain the on/off switch is in the off position and reinstall all tubes. Then connect A and B batteries via the input socket. Use banana plugs if a bench test cable is not available. Connect an antenna and counterpoise to the set and connect a 2000 ohm headset to the headset terminals. Turn the set on and if you are lucky it will work. I checked all four bands but got no signal other than the loud hum. The next step is to find the cause of the hum.

A. Remove detector, if hum continues, the problem is in the audio circuit.

B. If hum stops with the detector out, it is probably a problem in the regeneration control. Replace with a 100 K ohms Potentiometer.

C. If an audio problem, probably a by-pass capacitor

Regarding the audio oscillation. Check caps 45 and 46. They are the audio bypass caps. Just put the same value capacitor in parallel with them to see if that fixes the problem.

SEEKING INFORMATION ON THE JAPANESE TYPE 94-5 RADIO RECEIVERS

I have been examining several Japanese Type 94-5 Radio receivers and have found several differences in these sets. I am hoping to compile a more complete listing of these sets and a description of the sets. I would like to obtain the following information from your set(s) if you have any of these.

Serial Number, date of manufacture, presense of the code (PR 8F ) on the case:

Serial Number on the front panel of the receiver:

Location of Part No 20, a capacitor next to or in the rear of the band switch:

Metal can or Mica capacitor?

Location of Part No 20, a RF coil, normally on the back center brace, sometimes on the left of the band switch, sometimes missing.

Location of Part Nos 22 and 23, a joint set of RF coils, usually mounted on the left side of the band switch, sometimes missing:

Type 94-5 set "Jim Karlow on the air with his Type 94-5 set"

I got the 94-5 receiver fully operational. Thanks for your advice and help in the process as well as for parts and notes !

Actually the receiver is quite an impressive performer, considering its age. The unit I got working is actually a combination of parts from 3 units. I had to replace a transformer as well as several other parts.

I was able to find a working set of Japanese WW2 tubes that were functional, so I was able to run the original configuration. So, I listened to some 40 meter CW a little while ago, also some BC Band run up to the SuperBowl game that will play here later this afternoon. I'm still going to look at doing a solid state set of replacements for the tubes, but getting it going in original configuration gives me a good benchmark for making measurements.

Jim Karlow

A quick picture of the Type 94-5 radio set ready for the Dayton Hamvention !

Both transmitter and receiver function well on the bench, although I have not had the chance yet to test it outside with the antenna and counterpoise fully extended. As it is 25 degrees F here in Detroit I just layed the wiresout on the floor. The receiver is using a "D" cell flashlight battery for the filiments and 10 of 9 volt batteries strung together for the B+. I set the filiment pot on the radio for 1 volt on the filiment voltage test jack on the front of the receiver. 3885 KHz is about 50 on the main tuning on Band 4. I assembled a small speaker box with an amplifier and high impedence input that I connect to the auxilliary headphone jack so others can hear the receiver perform. For the transmitter, I wired up the generator and installed an external voltmeter so the cranker would know how fast to turn it. In case I run out of volunteers for cranking I have also mad up a transmitter battery pack, consisting of a 6 volt 7AH NiCD filiment battery and 15 nine volt transistor radio batteries in series. I made an 88 foot antenna and a 50 foot counterpoise, per the Signal Corps Technical Bulletin.

Receive sensitivity is excellent. Measured with a HP 8640B signal generator,1.5 uv is audible at 3885 KHz. I crystal controlled the transmitter using a surplus 3885 KHz crystal in an FT243 socket mounted on an adapter to fit the Japanese crystal socket. The carrier output looks reasonable when checked with a spectrum analyzer with a short whip antenna. The CW output wave form looks good, although the unit seems to be a little light on modulation in the voice mode. The RF ammeter doesn't seem to move much, but it may work better when I get the antenna more optimally positioned. I have been rehearsing with this for a couple of days now and am getting used to how it operates.

The local old military radio net at Dayton will be on the Saturday of the Dayton Hamvention at 12:00 Noon on 3885 KHz, AM mode. While most of the guys will be using the Amercan stuff (BC-611, BC-745, BC-474, BC-654, MAB, DAV etc), this will likely be the only Japanese WW2 rig on the air.

Thanks for all of your help !

Maybe you can join us.

All the best,

Jim

Type 94-5 radio set ready for the Dayton Hamvention

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Tom Dennis's Type 94-5 Receiver

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Tom Dennis sent these pictures of a Japanese military receiver. His dad, who was a radio operator in a PBY reconnaissance aircraft in the Navy during WWII, obtained it and gave it to him as a fledgling ham radio buff. It is a 3 tube regenerative receiver powered by 1.5V and 90V batteries. It's frequency range, per the charts visible in the lid, is 400khz - 6000Khz. A set of headphones and 2 extra tubes, one still with its box, can be seen in the pictures. There are also schematics under the charts.

In one of the pictures, a cap has come off of one of the tubes in the radio and has been replaced with an alligator clip which is connected to the wire that remains on top of the tube. Using this fix (done by me 40 years ago), and external power supplies, the receiver still works.

Tom Dennis

Naperville, IL

Picture Gallery - Variations in these sets:

One variation in the transmitter which has been observed was a set with a canvas flaps rather than the standard leather flaps. Shown below is this version.

For More Examples and Info Click Image