8mm Forum: Elmo-St-800 Potentiometers

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Topic: Elmo-St-800 Potentiometers

William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted December 23, 2015 03:34 PM

OK So my wonderful Elmo ST-800 has just been damaged by me. I was adjusting the 2 potentiometers in the circuit board to adjust speed and they broke. Anyone know the specifics of these potentiometers and where I could get them? This pic is not mine. I got it from the internet.

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted December 23, 2015 03:40 PM

Tell you what...

I can either measure mine or try to read a value off of them.

(Coupla' days...It's Christmas!)

I actually wouldn't replace them with the same parts. These aren't even a full turn from one end to the other. This makes the adjustments very twitchy. You give it a little twist and you go from too slow to too fast. You turn it back and now it's too slow again.

I can find you a more modern 20 or 25 turn pot: much more precise and less frustrating too. (Save your patience for something else!)

Ho! Hooooo!!!!

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All I ask is a wide screen and a projector to light her by...

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William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted December 23, 2015 05:03 PM

Thanks. I appreciate it. I know what you mean about them being twitchy.

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Andrew Woodcock
Film God

Posts: 7477
From: Manchester Uk
Registered: Aug 2012

posted December 23, 2015 05:22 PM

Steve really is a true ambassador of our great hobby.
He and Janice always go to great lengths to help anyone out here.

I think a special mark of recognition ought to be given here, for all their totally unselfish acts given out 365 "for the love of the game" so to speak, of our truly fabulous hobby!

Well done you guys!! [Smile]

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"C'mon Baggy..Get with the beat"

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William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted December 23, 2015 07:18 PM

I second that emotion!

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Martin Jones
Phenomenal Film Handler

Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008

posted December 24, 2015 01:49 AM

Best wishes for Christmas and the New Year to all Members and Friends.
Martin

--------------------
Retired TV Service Engineer
Ongoing interest in Telecine....

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted January 03, 2016 10:05 PM

Coupla' Days turned into a week!

OK, the two pots are two different parts, different values.

The one to the left is 40K. I found a 50K 20 turn pot which will do the job:

50K Pot

In order to hook it up properly, the center terminal would need to be connected to the leftmost one.

the other one is a 1K:

1K Pot

It's a direct hookup: right, center, left.

Both of these have the terminal on the top. I think the best thing would be to lay them on their sides and tack them down to the board with something like RTV. That way the adjustment screws will be pointing outwards towards you.

The best means to do the adjustment is some kind of plastic driver like this:

Bournes H90 Adjustment Tool

They stay on the adjustment screws better and you aren't fishing around live circuitry with a metallic tool!

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All I ask is a wide screen and a projector to light her by...

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William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted January 04, 2016 10:35 AM

Thank you Steve. As usual, you've gone above and beyond. No need to apologize for any delay. Happy New Year!

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted January 04, 2016 10:46 AM

It's sad: I actually had the week off from work!

-my greatest achievement may have been the morning I slept until 10:00. (I haven't done this since college!)

I did assemble the new snow blower...what fun!(?)

-my old one jammed if I hit the newspaper (...and I did!)...this one may blow shreds across the yard!

My advice is before you go to adjust (-even before installing them...) turn the adjustment screw to a limit ("click,click,click...")and then turn it opposite about 10 turns to get right in the middle of the range.

This way you won't start up the machine at some whacky frame rate, but at least in the neighborhood.

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All I ask is a wide screen and a projector to light her by...

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William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted January 04, 2016 12:59 PM

Thanks for the advice.

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted January 04, 2016 01:05 PM

If you really want to go for it:

Remove the old ones from the board first and measure the values. I had to measure them in-circuit and that introduces the shadow of a doubt.

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All I ask is a wide screen and a projector to light her by...

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William Olson
Master Film Handler

Posts: 287
From: Poughkeepsie, NY USA
Registered: Jun 2010

posted January 05, 2016 10:20 AM

OK Thanks.

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