Pro Audio Design Forum

Wayne..somehow I recall that you are a App Engineer for THAT Corp. But whatever...

Thought you may get a kick out of this item I recently completed.

http://recordingservicesandsupply.com/i ... d=44716247

VERY specific for a small market, but I'm already re-ordering PC cards, since the original small run sold out in 48 hours...<g>.

Bri

Very cool Brian.
Otari parts are in very high demand.
Yes I did, and still occasionally do, app work for THAT.

You wanna make an optical tach replacement for a JH-110/JH-24? (Yeah I realize they were all 110s.)
I happen to have a schematic of one I designed using an Avago code wheel and quadrature detector.
Its a drop in replacement that requires no mods to the analog torque board other than a power tap-off.

mediatechnology wrote:
You wanna make an optical tach replacement for a JH-110/JH-24? (Yeah I realize they were all 110s.)
I happen to have a schematic of one I designed using an Avago code wheel and quadrature detector.
Its a drop in replacement that requires no mods to the analog torque board other than a power tap-off.

Is that a replacement for the "slot car motor" DC tachs attached to the back side of each reel motor? If so, that sounds pretty cool, since the OEM tachs are all getting glitchy due to decades of wear on the (now unobtanium) carbon brushes.

Bri

Yes it is.


Avago MCI JH-110 Optical Tach Modification

The Avago optical quadrature reader mounted to the existing aluminum triangular plate and the metal code wheel, mounted into the existing real motor.
There was a F-V convertor circuit with DC output polarity determined by direction of rotation.
To the torque board it looked just like a DC tachometer.
Other than the mechanical aspects of adding the encoder and PC board the only "mod" was to get a +/-15V supply to the F-V board.

I tried one of the optical tachs paired with a DC tach on a 1/4" JH-110 and the machine worked like a champ.
It didn't notice any difference and MVC seemed to work better.
That was a protoboard and I never did a PC.

But I filed it away because you could still get brushes, it was the mid 90s and people were just beginning to abandon tape.
Now you can't get brushes.