Problem with GAF 1788Z dual 8 projector

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Doc - 05 Dec 2004 08:35 GMT

Hoping someone knowledgeable about 8mm projector function/repair will be
able to help.

I recently got my parents' 70's era GAF 1788Z dual 8 projector out of
mothballs. The old main drive belt had gotten hard and broke so I replaced
it but it's still having problems. As far as I can tell all the O-ring type
belts are in good shape, the gears/pulleys are all sound, I don't see any
broken springs etc. The projector actually has very little use, it was only
used a couple of times.

The problem as far as I can determine is that the take-up spindle isn't
being engaged when the projector is in FWD. The spindles themselves are
turned by free-spinning disks on the inside end of the shafts that are
supposed to engage rubberized edges on the outside of nylon wheels.
However, in FWD, the rubber edges don't engage though they do in other
positions.

Any insights, suggestions? If needed, I can take pics and post on a website.

Alternately, anyone know where I can get a service manual for this projector
model?

Thanks for all input.

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t.hoehler - 05 Dec 2004 15:51 GMT

The problem is probably the rubberized edges on the nylon wheels. Similar
problem with rim driven turntables, the rubber gets hard and glazed. The
surfaces contact each other, but there is not enough friction to get the
power transferred. Maybe Bill T can resurface those wheels for you.
Regards,
Tom

> Hoping someone knowledgeable about 8mm projector function/repair will be
> able to help.
[quoted text clipped - 19 lines]
>
> Thanks for all input.

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William Sommerwerck - 05 Dec 2004 15:22 GMT

> The problem is probably the rubberized edges on the nylon wheels.
> Similar problem with rim driven turntables, the rubber gets hard and
> glazed. The surfaces contact each other, but there is not enough
> friction to get the power transferred. Maybe Bill T can resurface those
> wheels for you.

There are also rubber-rejuvenation chemicals.

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Doc - 05 Dec 2004 21:24 GMT

> The problem is probably the rubberized edges on the nylon wheels. Similar
> problem with rim driven turntables, the rubber gets hard and glazed.

The rubber on the edges of the wheels is in good condition, the problem is
they're simply not being shoved into contact with the driven disks on the
ends of the spindles when the selector is in the FWD position. There's a
substantial amount of daylight between them. If I shove them into place
with my finger, the spindles turn fine. I've studied the mechanics of this
thing until my eyes crossed, so far haven't divined why this is so. Nothing
seems to be obviously broken or out of place. All belts are in place, from
what I can see so are the springs. But, obviously there's a reason it's not
doing what it's supposed to do.

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NSM - 06 Dec 2004 00:48 GMT

| > The problem is probably the rubberized edges on the nylon wheels. Similar
| > problem with rim driven turntables, the rubber gets hard and glazed.
[quoted text clipped - 8 lines]
| what I can see so are the springs. But, obviously there's a reason it's not
| doing what it's supposed to do.

In that case I suspect that continued study will lead to an 'Aha!' moment.

N

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Nelson Gietz - 06 Dec 2004 01:57 GMT

> | > The problem is probably the rubberized edges on the nylon wheels.
> Similar
[quoted text clipped - 15 lines]
>
> N

Have you opened the back? Any chance a lever on the control shaft is
held by a set screw... and can be "set up" a bit?
Nelson

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Doc - 06 Dec 2004 03:35 GMT

> Have you opened the back? Any chance a lever on the control shaft is
> held by a set screw... and can be "set up" a bit?

Yes, have been looking at the guts all day. The "heart" of the whole thing
is the selector switch which turns a multi-cam unit that controls various
elements of the mechanics. Quite an ingenious arrangement. Unfortunately it
appears something's not working right and damned if I can figure out what it
is.

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NSM - 05 Dec 2004 19:16 GMT

| Hoping someone knowledgeable about 8mm projector function/repair will be
| able to help.

...

| Any insights, suggestions? If needed, I can take pics and post on a website.

As a test, I'd try a light coat of rubber cement on the wheels and let it
dry. It may not last, but you can at least see if there are other problems.

| Alternately, anyone know where I can get a service manual for this projector
| model?

Did you Google for it?

N

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Doc - 08 Dec 2004 23:07 GMT

> As a test, I'd try a light coat of rubber cement on the wheels and let it
> dry. It may not last, but you can at least see if there are other problems.

If anyone's interested, I finally divined what the problem was. After
watching the way
everything behaved for the umpteenth time, it became apparent that once upon
a time there was some rubber on the shafts of these grey wheels that I was
wondering about, which apparently degraded and fell off so cleanly it didn't
even leave a piece behind so it wasn't immediately obvious there had been
rubber there. This was the only thing that made sense.

I cut a couple of short pieces of vacuum hose that fit tightly over the
shafts where the old rubber was and now it works like a champ. At some point
I might look for factory replacements but for now it seems to be doing okay.
While I was at it I also took out the film-guide and polished it with chrome
cleaner, cleaned the mirror and view aperture window (all my nomenclature,
not sure what the factory manual would call them) so now there isn't any
"fuzz" along the edges of the projected image on the screen.

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NSM - 08 Dec 2004 23:43 GMT

| > As a test, I'd try a light coat of rubber cement on the wheels and let it
| > dry. It may not last, but you can at least see if there are other
[quoted text clipped - 15 lines]
| not sure what the factory manual would call them) so now there isn't any
| "fuzz" along the edges of the projected image on the screen.

Interesting! BTW, it's a good idea to keep the gate clean as this is the
major source of film scratches.

N

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Tim Mullen - 09 Dec 2004 00:35 GMT

>Interesting! BTW, it's a good idea to keep the gate clean as this is the
>major source of film scratches.

I don't know one whit about the projector (Although it sounds like
the OP solved the problem righteously. Cheers!), but I'd like to
chime in about film. It's more fragile than you might think, and
scratches pretty easily. Handle by the edges, and all that good
stuff, and keep it away from dust and dirt. Don't leave spools
just lying around in the open.

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Tim Mullen
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Mike King - 24 Jan 2005 17:43 GMT

When I was in film making class (back when film making was done with FILM
not video equipment!), the more knowledgeable guys carried a little brush
and cleaned the film gate on the class projector before running their film
through the community machine.

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darkroommike

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> Interesting! BTW, it's a good idea to keep the gate clean as this is the
> major source of film scratches.
>
> N

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Tim Mullen - 25 Jan 2005 04:33 GMT

>When I was in film making class (back when film making was done with FILM
>not video equipment!)

Ummm... it still is.

By far, however, the most important part of making a film is
telling a story, not the equipment used.

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Ken Layton - 09 Dec 2004 04:42 GMT

The best place to visit for projector info and manuals is
http://8mmforum.film-tech.com
Also check www.craigcamera.com for a manual.

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