Grundig Stenorette and Stenorette 'S' (1955)

[Phil G4SPZ]

A local small industrial museum found this early dictaphone in their cellar. It was in filthy condition with a cracked case, but came with a microphone, footswitch and a reel of tape. The museum were very keen to hear what, if anything, was on the tape as it may have been the voice of one of the factory’s past directors.

Getting the sound off the tape was relatively easy. Some early Grundig tape machines record on the bottom half of the tape, and a quick inspection of the heads showed that this was no different. Tapes need to be played back at 1.875ips - fairly close to the average record speed of 2ips of the Stenorette - on a modern 4-track tape recorder switched to tracks 2-3. Sure enough, there were two passages of audio on the tape, which I captured and digitised for posterity, and the museum staff were delighted. They also expressed an interest in demonstrating the Stenorette, if it could be made to work, so I (perhaps unwisely) volunteered to have a go at it.

Visual inspection suggested that the machine was either a “Stenorette” or a “Stenorette S”, both visually almost identical but with significant internal differences. I obtained some circuit diagrams (in German) from Radiomuseum, but the best one I found was in my 1965 copy of Newnes’ Tape Recorder Servicing Manual by H.W.Hellyer, and after a brief study I realised that I was dealing with an early model Stenorette, having the valve line-up EF40, EBF80 and ECC82. One half of the ECC82 forms the bias oscillator, the other half forms the audio output amplifier. There are two DC supplies, nominally 200V for the valve electronics and 24V for the tape transport solenoids, both provided by separate contact-cooled bridge rectifiers, plus a 6.3 volt AC LT heater supply which also powers the pilot lamp in the tape position indicator and the recording lamp in the microphone.

On dismantling the machine, the bias oscillator coil L4's former was seen to be detached from its base and swinging around on its lead-out wires, so I glued the former back into position. Fortunately the connections were still intact. Mechanically, both the playback and fast-forward rubber-tyred idler wheels were seized solid, but these freed off with a spot of lubricant and some gentle persuasion. A Megger test via the two-core mains flex revealed nothing amiss, so I applied power via a lamp limiter. The motor spun up, the dial lamp illuminated, nothing got hot and no smoke appeared, so after a few moments I applied full mains. All the capacitors ran cool, so I tried playing back the tape.

The Stenorette has no capstan, relying on a large diameter take-up spool running at a constant speed to pull the tape past the heads at an average 2 inches per second. Playback speed was decidedly wobbly, but thorough cleaning of the rubber idlers and wheels throughout the rim-drive mechanism rectified that. The playback and rewind functions are operated by solenoids which move the various idlers into position, and whilst playback and fast rewind worked OK, I could not get the machine to fast forward, nor to backspace.

Fast forward wind is purely mechanical, the pushbutton moving a rubber-tyred idler under spring pressure between the large motor pulley and the take-up reel drive wheel. Slight adjustment of the spring tension cured that problem. Backspacing is an elegant function, involving brief engagement of the rewind solenoid under the control of an adjustable timing mechanism formed by 300uF and 500uF capacitors and a 1k potentiometer. The problem turned out to be dirty contacts within the footswitch, which were cleaned and adjusted. The 4-pin DIN plug on the footswitch cable was in a very poor state, so I bought and fitted a new one.

With the backspacing function now working, it quickly became apparent that there was insufficient tension in the take-up reel hub, because the tape kept spilling out. Both reels have clutch mechanisms which seemed to work normally, but with no brake pads, the right-hand take-up reel shaft appeared to need a degree of stiffness that just wasn’t present. Sure enough, below the deck the shaft incorporates a compression spring to generate the necessary ‘drag’, together with some fibre washers - which had crumbled to dust. At this point, I felt that I was going to get nowhere fast unless I obtained a service manual, and in response to a request on the Forum, Michael a.k.a. “LIVEWIRE” very quickly came up with an original paper copy of the service manuals for both the Stenorette and Stenorette ‘S’, which proved very helpful indeed. The Stenorette manual is dated 1.1.55 and the Stenorette ‘S’ manual 12.12.55, suggesting that the production run of the original Stenorette may have been less than two years’ duration.

With the benefit of the service manual I was able to dismantle and remove the take-up reel shaft, reassemble it with new fibre washers and adjust the spring to give improved tension. After refitting the shaft, I realised that I had managed to break a soldered joint from a capacitor to one of the pins of V2 - there’s very little space to work in there - and I eventually fathomed out that it was C11 which needed to be resoldered to pin 7, a very fiddly job but ultimately successfully completed.

So with playback, rewind, fast-forward and backspacing all working, it was time to try recording. I found an empty Grundig 3” tape spool - standard spools won’t fit, as the centre sprocket diameter is too large - and filled it with standard tape. The recorded audio was very crackly and intermittent, which I tracked down to a faulty recording sensitivity switch. As this item was a Grundig ‘special’, I searched for a replacement and was lucky enough to be able to buy a complete Stenorette ‘donor’ machine for just £4.99, which also yielded a perfect microphone and an undamaged plastic case. I replaced the sensitivity switch, and recording quality was restored. Pleased with myself, I resolved to replace the 2-core mains flex with a proper 3-core lead and then return the machine to its owner.

It is important to realise that this repair - I can’t justify the term ‘restoration’ - was undertaken over many weeks, bit by bit and one day per week, during my volunteer sessions at the museum. When I came into the museum the following week, armed with a new length of 3-core flex, I did a quick test and discovered that playback had disappeared. The mechanism was working, but no sound was coming from the tape. Study of the circuit showed that there are no less than nine sets of make, break or changeover switch contacts in the playback/record switching circuits, all actuated mechanically by the play and record pushbuttons. Very carefully, I cleaned (again) and inspected the contacts and discovered that the mechanical adjustment is critical, particularly contacts W2 and W4 which are in series with each side of the record/replay head. After a lot of fiddling around, I had restored both playback and record functions.

The following week I replaced the mains flex with a 3-core lead, using a convenient chassis bolt to clamp a solder tag to provide the earthing point. On subsequent testing, the deck refused to go into playback mode. On close inspection, a wire had come off the playback solenoid and there was evidence of a dry joint from manufacture. I had probably disturbed it whilst fitting the new mains lead. That fixed, playback was restored but I found that I had lost the record function again! After a protracted period of continuity testing, head-scratching and profanity, I found that leaf switch contacts A5 were to blame. The mechanical adjustment of all these contacts is absolutely critical, and I dare say that this is one of the reasons that Grundig introduced the successor model Stenorette ‘S’ which has a single multi-contact relay to undertake the record/playback switching... of which more later. I was happy to be able to refit the covers for the last time and prepare the machine for return to its owners.

At some point during this protracted repair, I attended the 2016 NVCF and spotted another Grundig Stenorette for sale irresistably cheaply on the Bring & Buy stall, so I bought it as a potential source of spare parts, only to discover that it was the slightly later Stenorette ‘S’ model. Mechanically identical, with the same forward and reverse solenoids, the ‘S’ model’s valve line-up is EF86, EBF80 and ECC82, but it has fewer switch contacts operated by the pushbuttons as it has an additional master ‘K’ relay performing all record/playback switching. This ‘K’ relay also allows sophisticated remote control, backspacing and editing functions, all controlled from the microphone. Apart from being dirty, this machine was in good mechanical condition and came with the later-style single spool tape cassette (as opposed to the open reel of the earlier Stenorette) and the type 502 microphone with built-in corrector button. A 3-core mains lead was already fitted. I lifted up the tape cassette and it came apart in my hand; there must have been some sort of circlip, now missing, which originally held the spool of tape inside the cassette housing. I found that a suitably-sized rubber O-ring served the purpose just as well, and reassembled the cassette.

The machine powered up normally, but the tape transport wouldn’t function in playback mode. The multi-core mic lead was badly frayed and twisted where it enters the microphone casing, so I dismantled the mic and checked the cores for continuity. Sure enough, the two cores for the ‘start’ and ‘recording lamp’ functions were open-circuit, so I cut off the last six inches and re-terminated the lead, again a fiddly job due to the nature of the wires - stranded copper wire with double cotton or silk covered insulation - and the lack of space within the mic casing. Eventually I had the microphone working.

The backspace/edit function, operated by pressing and holding the button on the top of the mic, is quite interesting in that when pressed and held during recording, the machine reverts to playback mode, mutes the audio, backspaces and then automatically starts to replay. When the backspace button is released, the machine changes back into record mode. Again, all this is controlled by relay logic and R-C timers, and is operated by two buttons on the hand-held microphone. Apart from a light clean-up and minor lubrication, the machine itself needed very little work.

Over the past few months - I never rush things - I have got to know these early Stenorette business dictating machines quite well. Launched originally in 1954, they were imported into the UK in large numbers and seem to turn up at modest prices. Audio quality is acceptable for speech, the frequency response apparently extending to beyond 5kHz, with AGC on record and adequate microphone gain in ‘conference’ mode to record the proceedings from within a meeting room. I’ve tried this in practice and it works very well. The remote control functions were quite sophisticated for the mid-1950s. It appears that Grundig soon switched from valves to transistor electronics when the Stenorette ‘T’ was released in around 1959 - I can clearly remember my father using one of these, dictating reports when working from home in the mid-1960s.

Phil

[G4XWDJim]

Blimey Phil, you must have the patience of a saint. I could have helped with the head-scratching and profanity though. Fiddly looks to be an understatement.

Good write up thanks, you must be the forum's star success story writer.

Where did the word Stenorette come from I wonder. Perhaps from Stenographer?

Jim

[Kevin Hoyland]

Hello Phill.

Has always first class write up and Outstanding work. I had to smile when you said you take your time, i have been working on my RCA CR91 for the last 6-7 weeks.

Thank You Phil I look forward to all your write ups.
Kind Regards.
Kevin

[Phil G4SPZ]

Hi Jim and Kevin, and many thanks for your kind comments. The word Stenorette is actually a registered trademark of Grundig Business Systems, Jim, and as you say it's probably a corruption of Stenographer, originally meaning a shorthand writer. The machine being physically small compared with a human stenographer, hence hinting at the meaning "a little stenographer". No doubt Grundig coined the name in preference to something like "Magnetophondiktatapparat" which would have sounded rather too Germanic for the international market less than ten years after WWII!

[DOFFERY]

Phil,
You brought back my days looking after stenorettes for various government departments \& local solicitors back in the early 60's.Only a few months ago I offered a host of spares for these machines, no takers so alas dumped. I still have an "L", SL & several of the later models. I don't know if you are collecting but the machines I still have can be had F,O,C, also many accessories mikes,RCF units etc.

Colin.

[Phil G4SPZ]

Thank you, Colin - you have a PM.

[PaulR]

I used something very similar when I first started work. It was quickly replaced by a similarly sized grey plastic version which lasted for years to be replaced in the end by one that took tiny cassettes and was hand held.

The tapes in those cartridge things got worn out at the beginning where they were used over and over again, but with a bit of enterprise you could re-wind them so that the end was transferred to the beginning. I seem to remember they had a strip of metal towards the end of the tape that made a buzzer sound so you knew you were getting towards the end of the cassette.

The description of the action of the playback button brings back memories of trying to fathom out how the thing worked. An "old" lady in the office (probably in her mid 50s) used to tell me about a version she had known that recorded onto a roll of acetate but I am not sure whether that was imagination on her part.

[Phil G4SPZ]

Agreed, the Stenorette was a bit quirky but that's part of its appeal! I've since obtained a few more reels of tape with moderately interesting dictation still on them. After transcribing the audio to typewritten form, the secretary was supposed to erase the tape by holding down the 'rewind' and 'record' buttons, which fast-wound the tape backwards past the DC-energised erase head, thus wiping the tape. Many secretaries didn't bother.

My wife recalls erasing one of these tapes by mistake before transcribing it... she was fortunate to keep her job!

[PaulR]

Originally Posted by Phil G4SPZ

After transcribing the audio to typewritten form, the secretary was supposed to erase the tape by holding down the 'rewind' and 'record' buttons, which fast-wound the tape backwards past the DC-energised erase head, thus wiping the tape. Many secretaries didn't bother.

Yes I now remember that. We were usually left to do that bit ourselves. I did keep mine when it was condemned but later threw it away when having a clear out.

[stubbyeddy]

Originally Posted by PaulR

The description of the action of the playback button brings back memories of trying to fathom out how the thing worked. An "old" lady in the office (probably in her mid 50s) used to tell me about a version she had known that recorded onto a roll of acetate but I am not sure whether that was imagination on her part.

She was right i had such a machine in the past, I got it at a car boot sale when i was a kid, it looked just like a typewriter but on closer inspection when opened up i noticed it was something different, so i paid the 20p and took it home. it operated by inserting a4 like sheets of tape into a slot on a long cylindrical drum that was a bit sticky! the tape head just tracked along the rotating sheet of tape, the microphone/playback/remote had a kind of back and forward spacing as well as all the usual functions you'd find in a dictation machine. if i remember correctly you could also write notes along the scale of rotating drum, it came with 4 sheets of tape and made very good clear recordings and playback. Never seen another one and sadly i chucked it out years ago...

[PaulR]

I wonder what date it was in use. She retired in the mid 70s so probably started work in the mid/late 30s.