MCI Sony JH-110 (JH-24) Optical Tach Replacement

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mediatechnology
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MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

This is a circuit I tested some time ago that uses an Avago (now Broadcom) HEDS-5120 encoder/code wheel and frequency-to-voltage converter to replace the MCI/Sony JH-110 DC tachometer.

Image
MCI JH-110 Optical Tachometer Encoder and Codewheel Assembly

The picture is pretty self-explanatory.
The encoder mounts to the existing tachometer plate.
A short piece of 3/16" rod stock connects the metal code wheel to the reel motor shaft. (Both have Allen set-screws.)

The part number for the encoder including 360 count per revolution wheel is HEDS-5120G05.

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MCI JH-110 Optical Tachometer Schematic © Wayne Kirkwood 2017.

This is the interface schematic.
I tested one channel on a JH-110's supply reel (or take-up I can't remember).
The other reel used the standard tachometer motor.
The JH-110 couldn't tell the difference.
No modification to the analog torque board is required other than adding power leads (±15V) to the interface.

The 4013 D flip-flops decode direction information from the HED-9100G quadrature decoder.
One phase of the code wheel is used as a clock signal to feed the LM2907 F-V converter. (TP1)
There are 360 pulses per revolution.
The first LM324 stage provides a gain of two.
The output voltage is related to the speed of rotation and scaled at the same voltage as the DC tachometer.

The second LM324 stage and Q1 (Q2) flip the output polarity when the direction of reel rotation reverses.
If I were building this today I would put a jumper for the direction control line to receive either the Q or /Q output.
I'm not sure why you'd need it but it seems useful.

The offset trim is set for 0V when the reel is at rest. (TP2)
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JR.
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by JR. »

Looking at my dad's old engineering notebooks from the 30's he was working on speed stability for motors used in film/audio recording... I expect some of the same principles involved, just better technology these days.

JR
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mediatechnology
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

I expect some of the same principles involved, just better technology these days.
Yes, same principles.
The 1970s-era MCI JH-110 analog torque board was a pretty advanced analog DC computer that was poorly implemented with bad IC sockets, "Molexia," noisy DC tach motors, silver-leaded and oxidized stinky ICs, boards washed in consumer dishwashers and a lot of other ills.
I fixed a lot of chronically ill machines with new sockets, clean ICs, solder and pipe cleaners for the Molex female sockets. Lots of solder and flux remover.

Sony later ditched the JH-110 and JH-24 legacy transport and built the APR-24 using microprocessor-controlled transport and LOGDAC audio adjustments.
It was an awesome machine.

In 1992 I saw that tach motors were getting really expensive and did this circuit.
I published it in 2006 or 2007 to a great collective yawn.
Yesterday, after doing it 25 years earlier, I got asked about it.

I miss the smell of Ampex 456.
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by guy_478310 »

A big " Thank You" , Wayne, for searching your files and resurrecting this nice project ! :)
I hope to get time soon to experiment with this on some JH-24 / 110's ...
The Tacho signal from the spooling motors is a big concern on these machines...
Best,
Guy
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mediatechnology
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

You're welcome Guy.

The one thing I can't remember is tach motor polarity.
Are the supply and take-up wired the same?

IIRC they used an absolute value circuit on the analog torque board so it wouldn't matter.

There's a lot after 25 years I don't remember.

If the supply and take-up require different polarity you can add jumpers on the D flip-flops' Q and /Q outputs to reverse it.
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by guy_478310 »

Looks like the 360 count per revolution Encoder and Wheel parts Ref. HEDS-5120G05 are not available anymore... :(
Some other parts are available @ Mouser and Digikey but with different count per revolution.
Any possibility to adapt one here ?
Best,
Guy
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

I think all you have to do is scale the 39KΩ resistor connected to the LM2907 frequency to voltage converter.

How many CPR do they have available?
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by guy_478310 »

Farnell has 500 CPR available HEDS-5120#A06
They say that AVAGO is manufacturing from 96 to 1024 CPR on an 11 mm optical radius, and 500 to 2048 on a 23,36 mm optical radius.
Mouser & Digikey have 1000...5000 CPR
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

You should be able to make a 500 CPR work by scaling the resistor by 1.38.
The LM2907 datasheet is here: http://www.ti.com/lit/ds/symlink/lm2907-n.pdf

The more difficult problem is the "06" 1/4 shaft.
You'll need to adapt the 3/16" i.d. motor shaft to the 1/4" codewheel.
Maybe have some 1/4" stock turned down to 3/16" at one end.
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Re: MCI Sony JH-110 (JH-24) Optical Tach Replacement

Post by mediatechnology »

JR. wrote:Looking at my dad's old engineering notebooks from the 30's he was working on speed stability for motors used in film/audio recording... I expect some of the same principles involved, just better technology these days.

JR
I remember this post well. viewtopic.php?f=12&t=168
Looks like a TOPS patent notebook.

Image
September 27, 1932.
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