Rim Drive Tape Recorders


Rim Drive tape Recorder Mechanism

What is a rim drive tape recorder?

It was a small tape recorder which employed a very economical way of pulling magnetic tape past a tape head. This was done merely by turning the reels of tape.  These mechanisms were mainly found during the early to mid 1960s on Japanese made battery powered tape recorders.


Capstan Drive Tape Recorder Mechanism

What is a capstan drive tape recorder?

For the vast majority of audio and video tape machines (cassette, cartridge, and open reel) the tape is usually pulled past the recording head via a capstan. This is a rotating shaft protruding up from below the recorder’s deck. The tape is pinched between the shaft and a rubber pressure roller. This enables the tape to be pulled past the tape heads at a uniform velocity. The other end of the capstan shaft is press fitted into the center point of a large weighted flywheel. A belt is stretched between the flywheel and a synchronous motor.

On a rim drive tape recorder, each tape reel is set onto disks of equal sizes that have a rubber edge. The rotating motor shaft contacts the rubber edge of the disk which turns the disk thereby turning the tape reels. When playing or recording, it is the take-up reel that pulls the tape past the record head. As one can imagine, the tape speed increases as the take-up reel fills up with tape. Also, because of the variances in how the tape is wound on the take-up reel, there is noticeable distortion caused by wow and flutter which is slow or fast variations of a tape’s velocity.

99% of all wire recorders also use a method similar to rim drive in that as the wire fills up the take-up reel, the wire speed increases. However, because the large size of the take-up reel and wire being so fine, the increasing wire velocity, wow and flutter are far less noticeable.

As for these cheap rim drive tape recorders, their popularity began in the early 1960s in Japan shortly after transistor technology was introduced. These recorders were very simple 4-transistor machines. They were basically toys – and were imported into the US from Japan.

These rim drive recorders had an advantage over their bulky expensive tube-type counterparts in that they were small battery powered portables. A good battery powered consumer tape recorder was – well, they really weren’t all that affordable. In the early 1960s, we’re talking an average of 80 to $90.00 for a simple consumer grade recorder. What cost $80 in 1963 costs $665.00 today – about the cost of an average cell phone.

When I saw these little rim-drive tape recorders advertised in a 1964 Christmas toy catalog, they had an average price of $19.00 which is $160 today.


Universal Brand 3-Inch Reel to Reel Tape Recorder

I had one very much like the one above. This one here is one I got in 1993 at the art museum rummage sale held at the convention center. This is where I also found my first Wire Recorder. The above recorder was new in an unopened box packed in Styrofoam. Yep, in 1964 when this one was made, the Japanese packaged these recorders in this white toxic smelling rigid foam like stuff.

In the five or so short years when millions of these things were sold, there was a proliferation of different name brands. Most of these recorders were almost alike with few variations in the placement of the various components. I suspect the Japanese did then what the Chinese do now in that a lot of rebranding happened then.

When I was 13, I got the one I had from a guy who used it in the military to send letters to his girlfriend back home – at least that’s what he told me. This fellow sold me the recorder for $7.00. I had it for – I don’t remember what happened to it. I do remember that it stopped recording such that the sound was garbled. Playback of tapes was OK. The problem just affected the record function.


Erase Magnet     Record/Play Head


My Head Demagnetizer
From 1965
It was sometime while I was in high school when I happened upon it in a closet. I decided to try to get it to work. The first thing I did was to clean and demagnetize the heads – or rather its single head. Most of these recorders had a tiny permanent magnet that swung around to contact the surface of the tape to erase it as it was being recorded on. I then recorded something like “Testing 1, 2, 3…” I then played it back to find it recorded what I said as if it were new. It then dawned on me that the heads in these recorders became magnetized with use simply because there was no 30 kHz AC bias in the record circuitry.

In a normal cassette or reel to reel tape recorders, an AC bias is modulated by the audio signal. This combined signal then energizes the record head. The erase head just receives the AC bias. The AC bias serves to keep both tape heads demagnetized.


The Simplicity of Rim Drive

These recorders are hideously simple. There’s nothing inside except a simple 4-transistor push-pull amplifier board, a rotary switch, a slide switch, a speaker, a motor and some mechanically related pieces of metal to engage the motor.


An Example of the Ubiquitous 4 Transistor Push-Pull Amplifier

This is what the guy in the army paid a lot of money for so he could send his garbled voice across the Pacific to his girl. Back then, a $20.00 bill was an astounding whole lot of money to me. Today it’s worth $2.40. I wonder if he got married to her.

Anyway, the amplifier’s speaker output is what powered the tape head. The head was no doubt the most expensive part of this recorder. That 4-pole double throw switch is what switches the recorder from play to record. It disconnects the speaker; it disconnects the head from the input and connects it to the output, it disconnects the rewind function – just in case, and it connects the microphone to the input. Oh also, it mechanically moves the erase magnet onto the tape.

A 1964 Merry Christmas

When I was a young boy of 14, Christmas was proceeded by the yearly onslaught of toy catalogs. My sisters looked at dolls; my brother, the cars, trucks and plains; and me, the electronics, telescopes, and chemistry. Of course, when I was 12, I too sought Mattel cranes and other work vehicles. But when I got a little older, my interests turned to more scientific endeavors. Neither my brother nor I were into sports.

It was while perusing one of these catalogs when I happened upon an unusual tape recorder. Tucked away in my memory until more recent times was an unresolved… which was this tape recorder. In 1964, this anomaly seemed really unusual. I asked Dad if he would get me one for Christmas. After I showed him the catalog page, he flatly said, “No way!” For you see, this little toy cost $50.00 – which is $410 today.

Several years ago while at the Salvation Army Store, I happened upon something different, a weird tape recorder in unusually good shape. My wife then returned from Aldi with an arm full of food items, so I grabbed the recorder, laid a fiver on the counter, told the kind cashier to keep the change and I left with my apprehensive wife questioning another one of my purchases.

After I got home – well it was several days later when I had a chance to look at this thing.


Aiwa TP-1003 Stereo Rim-Drive Reel-To-Reel Tape Recorder

Yes, it was a stereo rim-drive tape recorder. My memory of the recorder in that catalog wasn’t all that clear, so I wasn’t sure this was the one I saw that day which caused the subsequent unresolved memory. But in checking around, I found this to be the only stereo rim drive ever made by any company.

Ok guys, its 1964 and mono battery capstan-drive reel to reel recorders were at least $300 in today’s dollars. But Stereo? What would a simple AC powered stereo tape recorder cost in 1964? Stereo was in its infancy then. So, a battery powered portable stereo reel to reel recorder was… I just don’t think they were all that common.

But, why this thing?


Two Identical 4 Transistor Push Pull Amplifiers

I’ve read a number of negative comments on various blogs as to why Aiwa manufactured this thing? The answer is not as complicated as one might think. I mean, after all, a stereo recorder is merely two sets of electronic components. In this one it is two amplifiers, two potentiometers, 2 sets of jacks, and two speakers. Instead of a 4 pole record-play switch, there’s a 6 pole switch. The only two components that might be a problem are the tape heads – one staggered track erase head instead of a magnet, and one staggered stereo head.

1/4th inch Staggered Reel to Reel Tape Head 1/8th inch Stacked Cassette Tape Head

Note. Cassette tape recorders used stacked heads and stereo reel to reel recorders used staggered heads. The reason cassette heads were stacked was for backward compatibility for playing mono cassettes.

Well, here it is Aiwa TP-1003 in all its plastic glory, leaky capacitors and all. After recapping the whole thing, it sounded interesting. I had to turn the rims down a couple of thousands on the lathe. But for a toy being 55 years old, it does OK.


Voice of Music Model 720 Hybrid Stereo Recorder

When I say interesting… When I was 12, I had no idea what stereo was all about. My uncle Charles brought over his VM tape recorder and one other tape recorder to serve as a second speaker. He set it all up for my dad to listen to. My dad then said, “Son, its stereo!” I kept going from one speaker to the other trying to hear a difference.

It was some time later while I was at a neighbor’s house playing when I discovered this beat up portable stereo record player – the kind where the turntable opens between the attached speakers and folds down. Its stylus was so bad that the music sounded scratchy and garbled. I started playing different 45 rpm records. I then played one that happened to be recorded in stereo. That’s when I discovered what stereo was all about. Even though the record player was tortured by the kids, it still played good enough to hear different sounds coming through each speaker. That’s when I said, I gotta have stereo.

Today this must sound stupid. But one has to remember, what we have today most of us in the early 60s didn’t have. HDTV, hundreds of cable channels, touch tone phones, microwaves, computers, the internet, mobile devices… Our zinc-plated vacuum-tube germanium-transistor culture was pretty primitive then.

Anyway, with all that in mind, this little recorder was rather unusual and was a joy – for some rich kid who got it for Christmas.

S April 7, 2019