CP J4 Zoom Control faulty

Gregg MacPherson · October 14, 2013

I recently got a Cinema Products J4 zoom control that only seems to run the motor at one speed. The motor(s) were I think used for a 35BL I. I wondered if the system had been tweaked with extra torque for that, but I don't think it can explain what I'm seeing.

The speed control pot in the electronics / battery box was corroded so I replaced that but it didn't change anything. In fact the motor behaved the same with the pot removed from the circuit. I measured V on the black/red wires going to the motor and pushing / pulling the thumb switch I got ....

- push ....12.5....12.8V

- pull ....-0.2.....-0.35 just after the start click, then staying at -0.35.

I had a quick look at the thumb switch internals. Thought I might leave it to an expert. I'm meeting one for another job soon.

Does anyone have a srvice manual or circuit diagram for the J4 zoom control? Any thoughts about what's wrong with it?

Cheers,

Gregg.

Gregg MacPherson · October 15, 2013

Shameless bump. Any thoughts appreciated.

Dom Jaeger · October 16, 2013

I'd say it needs to be looked at by an electronics technician (ideally one familiar with 80's era circuits), could be a faulty transistor, short circuit somewhere, maybe just a broken wire, who knows? If you had corrosion in the speed pot it could have got in somewhere else. Only info I've got is a price list from 1984 which tells me it cost $2200 back in the day.

If you have no luck locally, try contacting Glenn at synccine.com who does electronic repairs for us and can usually fix just about anything cine related.

Gregg MacPherson · October 16, 2013

I was hoping to meet Wes Printz soon for another small job (moved to Panvision Auskland from LA and good with electronics). So we'll see what he thinks.

Thanks,

Gregg..