Museum Hours:

Saturday 10-6

Sunday 12-5

Early Color Television

Gray Research Monitor for Closed Cuircuit Television

John Folsom acquired a Gray Research monitor in early 2014. Before he actually received it, he determined, from the pictures, that it was missing its motor control chassis. Using the one at the museum as a model, be began building a replica. It also appeared from the pictures that it was missing the alternator on the wheel shaft. When he received the monitor and inspected it closely, he determined that it never had a generator. Further inspection found that it had a 1800 rpm sychronous motor. Remington Rand made a closed circut field sequential system in the early 50s, the Vericolor. The motor was run from a 48 Hz source, resulting in a wheel speed of 1440 rpm. It is probable that this monitor was made for the Vericolor system.

Here are pictures, along with comments from John Folsom:

We started to do some comparisons with the schematic Steve made for his monitor at the Early Television Museun. Some differences in the tube lineup became obvious.  Video amp is a 6V6, not a 6BF5.   The audio output stage is two 50C5s whose plates drive the speaker mounted audio output transformer in push-pull.  There is a 3rd 50C5, whose function has not been determined.  The 3 50C5 filaments are wired in series and driven with DC from a selenium rectifier.

Most of the back apron connectors (except for the 2 AC receptacles) seem to be rather crudely cut holes and locations.   It has  an 11 pin octal style connector with only 8 pins used.  It has a 9 pin Jones plug with (I think) 9 pins used.

The other obvious difference is the 20 pin circular military connector.  Nine pins are used,   one of which is a coax feeding the volume control.  There is also a longish (4 foot) coax BNC cable coming from the cathode of the sync amp and passing out of the chassis through a ventilation hole at the top of the chassis.

At the end of the 3 arms of the motor mount assembly (below) was a shock mount rubber bushing with screw studs on both ends.

The foam piece at the end of the shaft in the above photo serves to make a soft seal plug around the wheel shaft and the hole in the face of the monitor in which the shaft protrudes through.  Should not be hard to mind a replacement material.

With the chassis removed, we were able to remove the color wheel.  Note its construction, the color filter film segments are riveted in place, like the RX43 (my) set.  I note that there are no balancing weights on the wheel. Cliff Benham commented' "On the riveted wheels extra rivets were used for "balancing" weights. This is true for the original DuMont Industrial color wheel and another unidentified wheel I saw at ETF.

The museum has a motor assembly apparently from a Gray Research monitor. It also has a 1800 rpm synchronous motor and no alternator.