8mm Forum: Pathescope gem 9,5mm projector restoration

This is topic Pathescope gem 9,5mm projector restoration in forum 9.5mm Forum at 8mm Forum.

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Posted by Sven Zijlemaker (Member # 2282) on March 13, 2011, 10:26 AM:

Hello,

I'am new on the forum, I will introduce myself, My name is sven zijlemaker, I come from the netherlands and I mainly am active on the 8mm format. But also with other film formats.

I'am trying to repair a pathescope gem 9,5mm projector.
The most of the work is already done. But the shuffle resistor doesn't work for 100%. About the half of the resistor has burned out.
So I only could choose 16 to 21 frames pro second.

Now I'am planning to rewire the resitor, but what kind of wire should I use for the resistor?
Resistance wire or blank tinned wire?
And if I should use resistance wire how much ohm per meter do I need, or with blank tinned wire how much mm is the diameter of the wire (I do not have the accurate instruments to messer the diameter of the wire).

Further more, I had found a loose piece of rubber in the 9,5mm projector.
It's about 5cm long and has a notch of about 3 to 4 mm.
Does someone knows where this piece of rubber could be for?
And I have also the problem with the mains calble, that the red wire is crumble at the plug. But it does not seems to be failing. Only the beginning of the wire looks to crumble.
I have heard many people rewire this part of the 9,5mm projector, but is it also need if the part that's go's to the 9,5mm projector still looks good?

And my last quastion, the rubber silence blocks on the base of the motor on my 9,5mm projector are complete decay. I already have some rubber grommets to replace the old rubber of the silence blocks, only the rubber grommets I bought (what could make out of the remaining parts of the old rubber silence blocks) are 2 a 1 mm longer than the old ones.
Would effect this the 9,5mm projector speed or does it not matter.
Thanks in advance for the help.

Sincerely, Sven Zijlemaker

Posted by Lee Mannering (Member # 728) on March 14, 2011, 03:45 AM:

Hello Sven
Around 30 years ago I also had the same problem you do and rewound the variable speed control as follows.

I used the wire from a electric fire element (old style) and carefully unwound it to match the length of the Gem variable resistance. You will need to take your time and rewind it very carefully which is critical but does make a nice and possible better job of it that Pathescope did. Once you have the wire in place you should seal around it with fire cement to keep the wire in place, but make sure you do not get it anywhere near where the brass slider moves up and down.

The break up of the old wire is not really caused by the slider moving up and down, it is more often than not caused by the old fire cement falling away and owners not replacing it to hold the wire in place. Once the cement has gone the wire breaks free and then starts to snap apart.

Hope the above is of help.

Posted by Dino Everette (Member # 1378) on March 14, 2011, 10:30 AM:

Sven
Also to address your final question, the only way the rubber motor blocks should affect the speed is if the difference in size would cause the inching knob to rub against the projector housing since the size of the original blocks placed it directly in the center of the port where it sticks out.

Posted by Sven Zijlemaker (Member # 2282) on March 15, 2011, 06:33 AM:

@Lee Mannering:

Hello Lee,

Thanks for you advise, I don't have a old electric fire element but I have found on the internet what possible looks on it, Isachrom 60 restance wire.
It has an diameter of 0,5mm and could manage a temperature up to 800*C.
A link to the webshop I had find the wire:
http://shop.conrad.nl/componenten/componenten-passief/weerstanden/weerstandsdraden/421201.html
Is this wire usable for the veriable speed control?

@Dino Everette:

Hello Dino,

Thanks for the advice it makes the repairing work some easier.

Sincerely, Sven Zijlemaker

Posted by Lee Mannering (Member # 728) on March 16, 2011, 05:34 AM:

There you have me. It was Frances Williams I think who used to write in Movie Maker magazine who helped me out with that knowledge so that is about as far as I can help you sorry to say.

Posted by Martin Jones (Member # 1163) on March 16, 2011, 06:00 AM:

Perhaps Dino (or someone else) could help by providing the following information...
1. The resistance value of an original GEM rheostat.
2. The cross section dimensions, and overall wound length,of the rheostat former.
3. The diameter of the original wire used.
4. What the spacing between turns is? (Or number of turns)

From that information, it is relatively easy to evaluate the wire suggested , which is 0.5 mm diameter and 5.65 ohms per metre length, or even to arrive at a wire type to use.
Martin.

Posted by Dino Everette (Member # 1378) on March 16, 2011, 01:09 PM:

quote:
Perhaps Dino (or someone else) could help by providing the following information...
1. The resistance value of an original GEM rheostat.
2. The cross section dimensions, and overall wound length,of the rheostat former.
3. The diameter of the original wire used.
4. What the spacing between turns is? (Or number of turns)

From that information, it is relatively easy to evaluate the wire suggested , which is 0.5 mm diameter and 5.65 ohms per metre length, or even to arrive at a wire type to use.
Martin.

Here are the gem specs on the original
2 - 42mm width & 65mm length (x2)
3 - original wire was .3mm diameter
4 - The original number of turns was around 145-150

1 - value = 100-105 ? ? ? did I do my math correctly professor?
[Confused]

Posted by Sven Zijlemaker (Member # 2282) on March 22, 2011, 01:26 PM:

Hello Dino,

Thanks for you advice.
I have measured the resistor on the part that was still function.
This was on the half of the resistor, there I measured 500 ohms.
Did you mean that the value is 1000 - 1050 ohms?
Further more, I have calculated that the length of the wire is 19.5m
I think I will use a resistance wire (not isolated) of 52,3 ohms per metre length (or 5,63 ohms per metre length), or should I use insulated resistance wire?
Is it necessary in the winding of the resistance, to leave small spaces between the threads?
Further more, I will use on the not isolated resistance wire fire cement on the top and bottom of the resistor.

Sincerely, Sven Zijlemaker

Posted by frank arnstein (Member # 330) on September 27, 2011, 07:53 AM:

So what happenned Sven?
No report at all about the resistor job?

Posted by Sven Zijlemaker (Member # 2282) on October 01, 2011, 09:50 AM:

Hello Frank,

The resistor worked for a part but I couldn't find the resistance wire for the resistor. So I left resistor in his original state. And after cleaning and oiling the projector I put the projector back together and tested the resistor of the projector. The variable resistor seen to work from the fastes speed to aprox 4 on the motor speed scale.
For the rubber mounting of the motor; I have replace them for old screws with some thick rubber rings between the space's.

After this I begane on the Pathescope H camera, here I also only came to cleaning the camera.
I already have tested two 9.5mm fuji velvia 50D films.

[ October 01, 2011, 11:01 AM: Message edited by: Sven Zijlemaker ]

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