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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 18th Oct 2020, 9:41 pm   #21
Ted Kendall
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Default Re: Sound Belle reel-to-reel heads

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Originally Posted by jmcilkley View Post
Presumably without a capstan the tape speed will vary as the diameter of tape on the right hand spool changes. This would make it impossible to play a tape from another machine that did use a capstan for constant tape speed. An unusual design!
Indeed so - and the wow is appalling. Nevertheless, this system was used on the Grundig Stenorette dictation machines, where a proprietary reel pattern ensured that only recordings made on that system would be played back, and on the stream of Japanese cheapies which appeared in the mid-60s, whose sole purpose was to record something recognisable at the lowest cost. With modern software, it is possible to straighten the speed out, using a recorded constant tone such as mains hum as a reference signal. The Japanese machines, however, had such puny motors that the take up reel slowed down as the pack diameter increased. Hence the motor drone of such machines is only a partial guide, and the final tweak has to be done by ear.
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Old 18th Oct 2020, 10:17 pm   #22
TIMTAPE
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Default Re: Sound Belle reel-to-reel heads

Rim drive if designed well didn't produce much wow even on music. The Stenorette was one example and the Philips dictation machines another. The later Philips mini cassette was also rim drive. I have an old Stenorette which only has speed issues now because the rubber parts have hardened over time. The older valve based Philips dictation machines using 3" reels in a cassette were particularly well made in my opinion.
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Old 18th Oct 2020, 10:40 pm   #23
Boulevardier
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Default Re: Sound Belle reel-to-reel heads

You seem to have shown that the playback amp is working by connecting your ceramic cartridge to it. I think you should now test whether the R/P head is actually generating any signal. The simplest way of doing this is by holding a tape-head demagnetiser against the front of the head. If you haven't got a demagnetiser, you could wind a coil of enamelled copper wire (say, from a junk transformer) onto a large nail, and feeding (briefly) ac from the valve heater chain into the coil. If the head is working, you will get a good 50c/s hum from the amplifier when the demagnetiser or the magnetised nail is held against the head.

Mike

Edit - sorry I'm not familiar with this machine, but I've assumed that it's a valve machine and that it has a 6.3V ac heater chain. Obviously, if it's a mains-fed heater chain, don't connect to this.

Last edited by Boulevardier; 18th Oct 2020 at 10:49 pm.
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Old 18th Oct 2020, 11:29 pm   #24
DMcMahon
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Default Re: Sound Belle reel-to-reel heads

Schematic shows 6.3VAC heater supply from transformer winding.
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Old 19th Oct 2020, 8:49 am   #25
jmcilkley
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Default Re: Sound Belle reel-to-reel heads

Sorry, Barry. I did see your post but I didn't understand the 2 coils bit. I was wondering if the 2nd coil was useable as the one being used is clearly defective. Without the wires connected to the head I can see the correct signals on my scope showing the bias at about 48k and sound from the microphone superimposed. With the wires connected to the head - nothing. So I'm sure the head is faulty.
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Old 19th Oct 2020, 8:57 am   #26
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Default Re: Sound Belle reel-to-reel heads

Very interesting posts, thank you all. Paul, your picture is exactly as mine (photo attached).
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Old 19th Oct 2020, 9:08 am   #27
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Default Re: Sound Belle reel-to-reel heads

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Originally Posted by jmcilkley View Post
Sorry, Barry. I did see your post but I didn't understand the 2 coils bit. I was wondering if the 2nd coil was useable as the one being used is clearly defective. Without the wires connected to the head I can see the correct signals on my scope showing the bias at about 48k and sound from the microphone superimposed. With the wires connected to the head - nothing. So I'm sure the head is faulty.
The two windings are wound round the two pole pieces so both are required to make a complete head. have you checked the continuity of each half?

The drive to a record head is normally more or less constant current so you would expect a big drop in level when you actually connect the head to the amplifier / bias signal though you should still see something unless the head is dead short, which would be unusual.
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Old 19th Oct 2020, 4:52 pm   #28
jmcilkley
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Default Re: Sound Belle reel-to-reel heads

Yes, you are right. Each half measures as 340 ohm, 680 between the points the 2 wires connect to. I don't really know if this is reasonable though.
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Old 19th Oct 2020, 6:06 pm   #29
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Default Re: Sound Belle reel-to-reel heads

Sounds plausible so the problem is probably not the head itself so as mentioned above, is the tape in proper contact with the face of the head - then try the induced hum from a demagnetiser or other field source as also mentioned above.

Remember, the output from a crystal (ceramic) pickup cartridge is many times the expected output from a tape head, so do not assume the replay amplifier is working properly.
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Old 19th Oct 2020, 10:25 pm   #30
jmcilkley
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Default Re: Sound Belle reel-to-reel heads

I'll try a coil from a sound source. I saw a video on how to do that on youtube!
The pressure pads seem ok and the tape does make good contact as far as I can tell.
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