8mm Forum: Weird GS1200 issue

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Posted by Dino Everette (Member # 1378) on February 21, 2018, 11:58 PM:

I have a GS1200 that is experiencing a weird speed issue, and I am curious where to look for a solution...Basically when I turn the machine on to watch a film the motor going forward either makes no movement at all or is dead slow, probably around 12 fps...If I hit rewind it is either full on 24fps or nothing at all, no movement.....I can run it for like an hour and then it seems like it will run at the proper speed and I can then watch a movie, but there is always the chance that if I stop the machine it might repeat the no movement issue...Once warmed up it will generally either go full speed 24fps or no movement at all....I have other GS 1200's that have a million other issues but the motors always start right up full speed. It reminds me of why I veered away from the ST-1200 with that slow start up....

Posted by Graham Ritchie (Member # 559) on February 22, 2018, 01:05 AM:

Dino

Try giving the ESS switch a good work out when the fwd is pressed and see what happens same for the 18/24 switch.

Another thing I came across with my spare GS1200 was I could not get 18fps... 24fps yes that was ok but not 18fps. It kept running a 6fps I found by giving the relay directly below the flywheel, a bit of a wiggle, that brought it back to 18fps...might be the contacts or a dry solder joint where the relay teminals go through the circuit board not exactly sure, but I am not game to touch it at the moment

Every thing speed wise is running fine now, but there is a lot to be said, for what fellow forum member Thomas did by replacing the motor and its contol...food for thought [Smile]

Anyway best of luck Dino, keep us all informed as to the outcome and hopefully someone else here can contribute with more help

Posted by Maurice Leakey (Member # 916) on February 22, 2018, 02:27 AM:

I have found that the GS-1200 does tend to be affected with dry joint problems, more so than other projectors in my collection.
I can't imagine that they were poorly made, was it constant use in their former lives?

Posted by Antoine Orsero (Member # 41) on February 22, 2018, 10:41 AM:

I had several GS1200 projector and most had electronic problems. I think these projectors are too sophisticated which makes them fragile! The ST1200 is simpler and more solid!

Posted by Chip Gelmini (Member # 44) on February 22, 2018, 04:58 PM:

I had a slow down issue just a few days ago. Messing around with the machine I suspected the “still” switch to be sticky. Contact cleaner worked well and it appears fixed but only time will tell.

Posted by Bill Brandenstein (Member # 892) on February 22, 2018, 09:25 PM:

Of all the things! Sorry to hear, Dino. Contact cleaner sounds like a quick and easy stab at a solution. But of all the GS problems I've seen, this isn't one of them. (Knock on wood!)

Posted by Thomas Knappstein (Member # 6134) on February 25, 2018, 02:06 AM:

Hello at all!
One of the biggest Problem for Speed Problems in the GS Machines are three little Diodes which are in line with one Main Motor Cable. They have 1 Ampere and the Main Motor need about 750-850mA when everything is fine. If there is less Grease on some Points the Motor need over 1 Ampere and the Diodes are running very hot and soldering out. Than the Motor stops or run slowly. Now I have replaced this three Diodes and changed them for a 5 Ampere Type under the Main Board. Now I can feel it with my Finger when this are going to hot and than its Time to greasing up the importand Points. Sorry for my bad english but i think some Photos will show whatI mean.

Posted by Renzo Dal Bo (Member # 5688) on February 25, 2018, 06:46 AM:

Thank you Thomas! A very precious suggestion here!

Probably to better locate the diodes, in their original position, you have to substitute the first photo with the following one:

[ February 25, 2018, 09:39 AM: Message edited by: Renzo Dal Bo ]

Posted by Graham Ritchie (Member # 559) on March 01, 2018, 01:44 PM:

Thomas or Renzo

Looking at those diodes what is the voltage or type number. The ones I can get locally are "ZR-1050...fast...100V..3A..Type FR302"...or FR307....also fast but 1000V...3A ...ZR1052.

If you could give the exact details of the diodes that would be great

Posted by Renzo Dal Bo (Member # 5688) on March 01, 2018, 03:02 PM:

The original diodes from the Elmo GS1200's circuit diagram are 1S1887 type: 400V - 1.0A.

Posted by David Fouracre (Member # 3883) on March 01, 2018, 03:37 PM:

I had a motor fault on my GS1200 which produced a pattern of motor stop, motor running slow and then running normally for several minutes.
I tapped the main motor with a small screwdriver whilst it was running slow, and it speeded up to normal for a few seconds and then stopped.
The problem was a worn set of brushes, which even under spring pressure were responsible for the erratic motor performance.

I sent the worn brushes to a company who produced copy replacement brushes with identical properties.
I had been tempted to file down some AC mains units, but was warned that low voltage DC brushes need to have a copper content to reduce wear on the commutator of a DC motor!
The replacement brushes arrived after a few days, were fitted, and the problem resolved. My GS was restored to full function.

David

Posted by Terry Sills (Member # 3309) on March 01, 2018, 03:55 PM:

I was tempted to buy a GS1200 many times because of the stunning looks and the technical specifications. Thank goodness I didn't. They are a nightmare of multiple problems. It seems they are just too sophisticated to be reliable. When one problem is resolved another rears it's head. Glad I stuck to mono sound machines.

Posted by Graham Ritchie (Member # 559) on March 01, 2018, 05:31 PM:

Thanks Renzo

I can get a 400V 6A ZR-1044 Type 6A4/P600G SSR..diode, would that be the ones Thomas mentions as a replacement?

Posted by Thomas Knappstein (Member # 6134) on March 01, 2018, 10:20 PM:

Hi Graham!
I used the BY 500/600 Diodes over 20 Years.

Posted by Graham Ritchie (Member # 559) on March 01, 2018, 11:08 PM:

Thanks Thomas [Smile]

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