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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 30th Jun 2018, 5:46 pm   #1
TonyDuell
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Default Agaphone Wire Recorder

I've currently got an Agaphone (also listed as Agafon on some web sites) wire recorder dictating machine on the bench. There seems to be very little technical information about this model on the web, so I will attempt to remedy that here.

There are 2 valves inside, an ECC33 and an ECC35 (yes, I do mean '33' and not '83', these valves are octal-based). So 4 triode sections. The ECC35 (both parts) and half the ECC33 form a 3-stage audio amplifier, the ECC33 being the output stage. The other half of the ECC33 is used in a Hartley oscillator circuit to provide bias/erase.

There is a neon indicator bulb on the panel. In record mode, this is biased just below the maintaining voltage (I think) and capacitively coupled to the anode of the output stage. It lights on strong signals, so I guess it's a crude level indicator. When you press the 'Signal' key, the neon is reconnected into a relaxation oscillator circuit which is used to inject an audio tone into the amplifier. As an aside I don't think I've ever seen the same component used as a level indicator and oscillator before.

The power supply is a double-wound transformer with HT (around 300V) and LT (centre tapped 6.3V) secondaries. The primary is tapped for various mains voltages with a tap-changer switch on the bottom of the machine. There's a conventional cartridge fuse in one mains wire to the transformer and a wonderfully heath-robinson thermal fuse in the other (consisting of soldered-together spring contacts in thermal contact with the transformer winding!).

The motor runs off the 110V tap of the transformer primary with a series resistor which is shorted out when the wire is to be moved. There are a pair of solenoids that move idler wheels to select forward wire motion or (faster) rewind. It appears the forward direction is right to left. A heart-shaped cap is geared to left hand spool, it moves the head up and down to give even winding of the wire.

The LT winding on the transformer is centre-tapped to ground. The valve heaters (obviously) run from the entire winding, the power-on lamp, which illuminates the wire position indicator, is run from half of the winding. The whole winding is bridge rectified (metal rectifier) and used to power the transport control solenoids.

The HT winding is half-wave rectified by another metal rectifier. Then capacitor, choke, capacitor to give the HT to the bias oscillator and output stage, Resistor and a further capacitor smoothing for the HT to the first 2 amplifier stages. The capacitors are in one 3-section can just in front of the transformer.

The only electronic control is a gain control potentiometer between the first and second amplifier stages. It is ganged to the mains on/off switch which is like the ones Philips used in the 1940s, a separate paxolin switch on the front of the potentiometer held on with 2 screws. You can separate them for cleaning, but note where the insulating sheets go. It's easiest to reassemble it with the switch 'on' and the pot turned fully clockwise.

There are 4 jack sockets on the unit. All are 3-conductor ('stereo') 1/4" ones, but nomally only tip and sleeve are used (ring is often connected to sleeve so a mono jack plug works fine). The ones on the right are for dictation/recording, the top one is a microphone input, I suspect for a crystal microphone. It cuts out the internal microphone when the plug is inserted. The bottom one is for a remote control switch, short tip to sleeve to have the wire run (of course the switch in the socket shorts those together if no plug is inserted).

The sockets on the left are for playback/transcription. At the top for a headset (which cuts out the internal speaker. Note also that the speaker is muted in record mode, but a headset plugged in there is not!). At the bottom is a socket for a foot control, this is the only one where all 3 contacts are used. Common, run forwards (play) and rewind.

OK, getting inside. The bottom cover comes off with the obvious screws and you can change the valves with it removed, but not do much else. To go further, take off the knobs (standard grub screws), take off the spring washer from the gain controland pull off the label plate (retained by a grommet round the neon). Remove the cap from the magnetic head and take off the wire cassette/spools. Take off the spool turntables (grub screw in each) and undo the 4 countersunk screws then revealed. Lift off the handle assembly, and then the main casing.

The unit is in 2 main sections, the deck and the amplifier. To separate them, loosen the 2 screws that clamp the loudspeaker to its bracket, unplug the head from the end of the tagboard over the valveholders and undo the 4 tubular nuts at the sides. The whole deck then lifts off, the motor and solenoid (and muting line) connections are a strip of spring contacts.

When I got mine, the mains switch had been very crudely bypassed. I cleaned it up so it works again and rewired it. In the process I decided to fit a new mains lead, 3 core (I do not like the idea of that metal case not being earthed, it may have been OK when new but I am not sure I want to trust old insulation!). As a result I didn't have to use double-insulated cable to wire the switch, just normal wire. I then desoldered the wire from the top of the HT rectifier and powered up. This let me check the transformer and LT circuits were fine (they were). Reconnected the wire to the rectifier, powered up again (no valves fitted). The HT came up with no problems, but worryingly there were 10's of volts on the control grids of some of the valves. Yes, 'Those Capacitors' were leaky. I changed them and others of the same type in the chassis. It's not easy to get to some of the tags, particularly on the record/play and Signal switches under the chassis.

After getting no more leaks like that I put the valves in and powered up. After they had warmed up I found touching the grid of the first stage with an insulated screwdriver had no effect, but doing the same to its anode produced noise in the speaker. Checking the electrode voltages showed that triode was passing no anode current. Turned out to be bad contacts at the valveholder. So the amplifier was fine.

I then tried record mode. The microphone is normally mounted in the middle of the speaker (I am not kidding) so it is obvious the latter has to be muted. But I removed the microphone and put it as far to the right side of the machine as the wire would allow. Then disabled the muting by grounding the sleeve of the earphone socket to the chassis. Tapping the microphone produced noises in the speaker and flickers from the neon (yes, an old crystal microphone that still works). The signal key produced a nice tone from the speaker too.

Just one more electronic section to check. The bias/erase oscillator. My first test was the voltage on the grid of its triode, connected to ground via a 15k resistor. I was getting a healthy negative voltage there, about -40V, which is a good sign that it's oscillating. And a 'scope showed it was.

So electronically I think it's right now. I've got the deck in bits at the moment (I'll post the details of how to do that if anyone is interested). One problem is that the forward movement solenoid is open-circuit. I've taken it out and unwound it. I also have some suitable wire (0.2mm diameter) to wind it with, but it's 728 turns (yes, I counted them as I took the wire off). So a fun job without a coil winder!.
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Old 1st Jul 2018, 2:27 pm   #2
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Default Re: Agaphone Wire Recorder

Although it appears that nobody else here has (or is interested in?) this machine, I might as well document how to dismantle the mechanism. It comes apart into 4 sections :

Top plate/head

Position indicator/heart cam, etc

Reel Spindle assembly

Motor/Drive assembly

With the mechanism removed from the rest of the machine, start by removing the 4 screws near the reel spindles on top. A metal disk round each spindle is now free, take those off. You can't separate the top plate from the rest yet as there is the linkage to move the head up and down still connecting them. Loosen the screw in the part fitted on the cam follower rod coming up from the position indicator, then reach in and hold the arm on the end of that rod against the one on the head, and pull it off the follower rod. Take off the top plate and separate the linkage arms. Note that there is a torsion spring there, it doesn't fly out but you need to see how it is fitted.

If you want to remove the head, start by measuring the position of the arm under the top plate from the end of the head support rod (17mm in my machine). Loosen the screw, slide off the arm and take the head out upwards. The cable will fit throug a tiny slot in the top plate.

Back on the mechanism, the next thing to remove is the position indicator dial. Loosen the 2 grub screws and it will pull off. It incorporates the locking spring for the clutch spindle (operated by pushing/pulling the left hand user control knob) so it takes a bit of force to get said spring out of the groove in the spindle. But don't damage the dial. There are some washers on the spindle that set the height of the dial, they normally stay in place but can be removed if you are worried they may get lost.

Next remove the 3 obvious screws and take off the position indicator unit. The follower rod just slides through the chassis.

On top of the reel drive spindle chassis, take out the 2 screws holding the tagstrip for the motor resistor. Free the grommet from the chassis. Turn the thing over and take out the 3 screws (one at each end of the contact strip, a shorter one at the front) that hold the motor unit to the reel drive spindle chassis. Note the earth wire!. Lift off the motor drive unit and recover the 3 washers (may be sticking to the rubber mounts).

Back to my unit. I have attempted to rewind the solenoid. Not having a coil winder, it essentially a scramble wind of as many turns as I could get on. It seems to work though. Testing is not easy, you can't fit the connector strips together without having the whole mechanism assembled, so I was connecting them with croc-clip leads. If you do this, be aware that the left hand 2 connections are 110V off the mains transfomer primary for the motor. You don't need these connected to test the solenoids, but you don't want to touch them by accident.
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Old 1st Jul 2018, 2:57 pm   #3
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Default Re: Agaphone Wire Recorder

I have often wondered how good these wire recorders where (are), I await the “It’s working and sounds like this” bit of your excellent post (photos?).
 
Old 1st Jul 2018, 4:08 pm   #4
TonyDuell
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Default Re: Agaphone Wire Recorder

I am taking photos as I go along, and will get them on my flickr account sometime.

My guess is that the quality is pretty poor, but we will have to wait and see. It is designed as a dictating machine after all, where provided the speech is understandable it is doing its job. It does use AC erase, it does (obviously) have an HF bias signal to the recording head. But there is no frequency equalisation in the amplifier. It's obviously spool drive (not capstan drive), but I think all wire recorders were.
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Old 1st Jul 2018, 9:39 pm   #5
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Default Re: Agaphone Wire Recorder

Quote:
Originally Posted by merlinmaxwell View Post
I have often wondered how good these wire recorders were.
Not terribly good, the weakest point being speed stability. Wow around 1% and dreadful speed drift are the norm. OK for dictation - just. This is not to detract from the intrinsic interest of the device, of course.
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Old 1st Jul 2018, 10:19 pm   #6
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Default Re: Agaphone Wire Recorder

If the take-up spool has a hub of diameter 80mm., then it will have a radius of 40mm. If we allow the wire to build up to a depth of 8mm., then the radius -- and therefore the wire speed -- will have increased by 20% over the full spool. But this is compensated for anyway by the action of the wire building up the same when listening as it did when recording.

However, we must assume there will still be a local error, due to the way the wire falls on the take-up spool. Let's say give or take up to two thicknesses of the wire as a reasonable estimate. If the wire diameter is 0.8mm, then an error of ±1.6mm. corresponds to 4%, or about a semitone either way. That is definitely noticeable, especially when the variation occurs rapidly as the wire lands on only approximately the right part of the take-up spool.
Quote:
Originally Posted by merlinmaxwell View Post
I have often wondered how good these wire recorders where (are),
I've seen one real one and several on TV and the Internet, and I believe the diplomatic way of phrasing the answer would be, good enough to persuade other people that they could do better.

Quote:
Originally Posted by merlinmaxwell View Post
I await the “It’s working and sounds like this” bit of your excellent post (photos?).
Link to a YouTube Video (with sound, naturally) even?
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If I have seen further than others, it is because I was standing on a pile of failed experiments.
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Old 2nd Jul 2018, 12:35 am   #7
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Default Re: Agaphone Wire Recorder

On later tape based dictating machines there was a control to vary the speed according to how fast the listener could type.
Recording speed was never an issue with dictating machines.
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Old 2nd Jul 2018, 7:56 am   #8
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Default Re: Agaphone Wire Recorder

Tony, is it a Swedish-built Agaphone/fon or one assembled by Thermionic Products at Hythe? It would be interesting to know how they differ. Photos please!
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Old 2nd Jul 2018, 12:10 pm   #9
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Default Re: Agaphone Wire Recorder

I believe it's the Swedish one. The plate round the controls labels the keys in English (Listen; Repeat; Reverse; Signal; Dict) but also says 'Agaphone Made In Sweden'. The lable on the bottom cover says 'Agaphone Type 399155-3 No 2315' and 'AGA Stockholm-Lidingo Sweden'.

Incidentally the motor plate (which has the top bearing of the shaded pole motor fixed to it, and also carries the motion control solenoids and idler arms) has an Electrolux nameplate on it. Alas I forgot to note the details before refitting the idlers and I'd rather not take them apart again if I don't have to.

Since I only have this unit, I can't compare it with a Thermionic Products one. I can check anything on my machine that you want to know, component values, layout, etc.

I'll get photos up on flickr soon, at least as far as I have got with the machine.
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Old 3rd Jul 2018, 10:22 am   #10
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Default Re: Agaphone Wire Recorder

Thanks Tony,

I don't have the T-P UK-built specs so not entirely sure which models TP assembled, including the paper/plastic-disc type. Not on 'flickr' so hope the photos will be on here too!

Barry
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Old 3rd Jul 2018, 12:45 pm   #11
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Default Re: Agaphone Wire Recorder

As an aside, I once saw, but didn't manage to rescue, a 'Thermionic' magnetic disc dictating machine.

Back to the Agaphone. I've dismantled the reel drive spindles. These run in a bush bearing at the top and a ball race at the bottom. If you want to take them apart, a good pair of circlip pliers saves a lot of bad language. Anyway, I've repacked the ball races with grease and put that back together. The ball races, BTW, are a standard size (6mm inside diameter, 19mm outside diameter, 6mm thick) and I could get replacements from RS for about £3 each if I need them.

Now got the position indicator in bits. This is geared to the tapeup spindle (worm on the botton end of the spindle to gear on a shaft running across the machine). This shaft carries a bevel pinion at the other end which engages with a bevel gear on the position indicator shaft when the latter is pushed in. That shaft carries the knob at the front end (going round a scale on the panel, also used to set the indicator to zero when the gears are disengaged) and an offset bush carring a spur gear whch fits inside an annular gear on the position indicator dial shaft and thus increments the dial position once per revolution.

The shaft across the machine also carries the heart-shaper cam and follower to move the head up and down to get even winding of the wire.

So I am cleaning all those parts, then I will reassemble.

And then I suspect I have to do the job that I am not looking forward to. The machine came with one 'cassette' containing 2 part-full spools of wire. Probably one spoolful partly wound onto an empty spool when the wire snapped. Alas both spools are tangled, I can't unwind either. So I have the 'fun' job of unsnarling the wire...
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Old 3rd Jul 2018, 12:52 pm   #12
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Default Re: Agaphone Wire Recorder

Quote:
Originally Posted by TonyDuell View Post
So I have the 'fun' job of unsnarling the wire...
This is next to impossible, and Heaven knows, I've tried. Best to clip at the wound pack on both spools and knot the ends together.
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Old 3rd Jul 2018, 1:08 pm   #13
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Default Re: Agaphone Wire Recorder

That's the problem. It's already in at least 2 pieces, one on each spool, and some very
short lengths that were tangled round the spools, spindles, etc and which I have thrown away (very short meaning a couple of feet at most).

But neither spool, removed from the 'cassette' will unwind by hand. I can get a couple of turns off, and then it jams. So I can't use either spool for recording as it is. I need to get at least one unwinding freely.
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Old 3rd Jul 2018, 3:43 pm   #14
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Default Re: Agaphone Wire Recorder

A bit more. I've cleaned and reassembled the position indicator/heart cam mechanism.

Next I re-fitted the motor assembly to the reel spindle chassis, and temporarily fitted the bare mechanism top plate to that. That meant I could fit the unit back into the main chassis and it would connect to the spring contacts at the back. Of course it didn't work when I tried it out, that would be too much to hope for. I found 2 main problems :

(a) The original solenoid (not the one I rewound) didn't always pull in, and had no effect on the idler when it did. After dismantling the mechanism again I found there are tabs on the armature to set the idle position of the armature and also one that hits the idler bracket. Careful bending of these got it to work

(b) The idlers were glazed and didn't drive the pulleys properly. I took then out again (at least it mean I could photograph the Electrolux nameplate on the motor unit) and rubbed them carefully with wet-and-dry paper. Yes, they probably are no longer prefectly round, but this is a wire recorder, not a transcription turntable, and I suspect any wow-n-flutter so caused will be inaudible over that caused by other issues.

Anyway, after reassemblng it, it then worked. I could select forward or reverse drive and the appropriate spindle turned.

Next the top plate came off again, the position indicator and head were refitted and the linkage between them (to make the head go up and down to give even winding of the wire) assembled. The mechanism was now fully assembled, so I put it back on the amplfieir unit and plugged the head in. Again the drive mechanism worked correctly, the head goes up and down as it should and if I carefully move a screwdriver near the head (agan, wire recorder, not Revox ) I get noises in the speaker.

So I think basically it now works. I do need to untangle the wire and try it out properly. But it's too hot here to fiddle with fine wire.
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Old 4th Jul 2018, 6:43 am   #15
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Default Re: Agaphone Wire Recorder

I'm not sure which is more 'fun': untangling a broken wire or a broken continuous tape-loop cassette. Both test one's patience to the limit! The wire at least retains its original dimensions.
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Old 4th Jul 2018, 9:55 am   #16
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Default Re: Agaphone Wire Recorder

I've done an endless loop cassette (in a telephone answering machine). The only way I found to do that was to undo the splice, wind the tape up, and splice it again.

Getting back on-topic, I've put some photos of the machine (not completed, so no photos of the casing, etc) in my flickr account here :

https://www.***********/photos/tony_d...57697010227661

I don't think you need any account to view them.
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Old 4th Jul 2018, 11:31 am   #17
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Default Re: Agaphone Wire Recorder

I have really enjoyed reading your account re the work you have done on this machine
you have imparted the real spirit of restoration
Monetary value is way down on the list of why we do these things
thank you
Trev
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Old 4th Jul 2018, 12:19 pm   #18
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Default Re: Agaphone Wire Recorder

What a lovely sequence of photos.
It reminds me of the tape based one I have got.
Little changed apart from the recording format once tape replaced the wire and germanium replaced valves.
Perhaps I should get it out and change the belts again.
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Old 4th Jul 2018, 6:07 pm   #19
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Default Re: Agaphone Wire Recorder

To Trevor, I have no interest at all in monetary value (of any of my collections). My interest is entirely technical. I want to see how things work, how problems were solved, and so on. A lot of the solutions in older technology are remarkably clever (a lot cleverer in my mind than just throwing a microprocessor at the problem...)

Anyway, I have come to the conclusion that the wire is evil. It is horrible to work with. It tangles if you look at it wrongly. It's springy. It's hard to see (if it is bent so it turns away from you, it looks like an end, so if you are not careful you try to pick up the wrong part). It finds anything in the workshop to get hooked round.

I have tried to start on the spool with the smaller amout of wire. I now have some short lengths, a large tangle (it did not help dropping the spool at one point...) and spool with more wire jammed on it. And I can't find how to get the other spool started at all. I much prefer tape!

I will try some more tomorrow. It's too hot for this really though...
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Old 5th Jul 2018, 1:42 pm   #20
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Default Re: Agaphone Wire Recorder

Quote:
Originally Posted by TonyDuell View Post
I have come to the conclusion that the wire is evil. It is horrible to work with. It tangles if you look at it wrongly. It's springy. It's hard to see (if it is bent so it turns away from you, it looks like an end, so if you are not careful you try to pick up the wrong part). It finds anything in the workshop to get hooked round...I much prefer tape!
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