GS 1200 Xenon issue

[Clive Carmock]

Wouldn't you know it now all three of my GS1200's have developed a problem!

The two standard machines - one makes a grinding noise after a while, possibly the toothed belt off the motor needs attention. The second GS1200 sufers sideways judder and subject of a separate thread here.

Today I wanted to run the Xenon machine.

Anyway the issue with this machine is that when switched to foward, the mechanism starts, the sprockets turn and the claw engages, the take up spol turns but the 'brake' on the feed spool does not release, meaning it can't turn to pay out the film and also the dowser does not open, and the magnetic sound head pressure pad does not engage. Usually these machines make a characteristic 'clunk' sound when engaging forward or reverse, but this machine does not do that. The magnetic head pressure pad is free to move when I push it manually, no resistance at all.

If I try the machine in reverse, again the mechanism runs but the doser does not open, also the feed sprocket does not turn, rewind runs the motor but the take up spindle does not turn.

I have subsequemntly found that the rewind and reverse running issue with the feed spool appears to be due to old very sticky grease. Having removed the feed spool arm cover I see the grease has turned a yellow/brown colour and is very sticky. I have managed to clean the white nylon gears, but it was hard going. Hot water and soap helped. Isopropyl alcohol doesn't seem to be that effective at removing it. I suspect the machine needs most of it's gears cleaning in a similar way and re-lubricating.

Does anyone have any recommendations for an effective cleaner for old sticky grease?

[Maurice Leakey]

Clive
Here a link to the old Forum regarding cleaning off grease.
8mm Forum: Cleaning and removing old grease/sticky levers question (film-tech.com)

[Clive Carmock]

Thank you for that link Maurice - I'll have a good read.

A little more on this issue. I have found it seems to be related to the release from auto threading. When the roller need the film exit is pushed back the loop former pops up, but the two solenoids do not trigger. If I push this roller further back both solenoids engage and it might stay that way but I see when this exit roller moves back a little both solenoids disengage again.

I must admit I would have thought once the microswicth on the exit makes contact after a light tug on the film it would trip the threading mode completely, but it seems not.

Not totally sure where to go with this next, but at least the solenoids are working and the circuit that drives them is OK.

[Lee Mannering]

Hi Clive. I would change the micro switch found near the metal film exit lever. I've changed so many of these in machines more than anything else I think when the threading mechanism won't release.

[Clive Carmock]

Thanks Lee - I have a pack of these microswitches on order now so will change it. Given it does correctly release the green auto thread 'button' at the top right but won't seem to always release the electronics to allow the solenoids to engage do you think it coudl still be the micro switch. I wonder since clearly the microswitch does something to release the button.

[Lee Mannering]

Yes I bet you a pound of sprouts it will be the micro switch.

[Clive Carmock]

I've removed the amplifier module from the projector, ready to replace the microswitch when they arrive tomorrow. I've notice that this one has a small ceramic capacitor solder across the terminals. It is marked 104. Would you advise that this is replaced at the same time? I'm unsure of it's value.

[Stuart Budd]

I don't know for sure but the auto feed is a combination of electrical and mechanical with an order of operation. I think the microswitch operates out of sync leaving the mechanical elements operating or not out of order.

https://youtu.be/SRXUDO-UOZY

My GS with a feed issue.

[Clive Carmock]

Interesting - the faults look different. In my case I find that if the rear microswitch is engaged and then released the threading mechanism releases from he auto-thread position, but as soon as I release the microswitch the head pressure pad opens and the downser closes again. I do notice the threading light top right comes back on too, so definitely not fully releasing from auto-thread.

I'm going to replace the rear microswitch as recommended by Lee to see if that helps.

[Clive Carmock]

Well I can see this machine is going to turn into a long saga! I have fixed the auto threding release problem. I still plan to replace the rear microswitch as I can see some oxidation on the contacts which likely indicates the same inside. Howeve the issue turned out to be near the front microswitch, the one engaged when the green thread button is pressed down. When the mechanism tried to release the auto thread the green button released OK but the metal arm that presses on the front microswitch started to move down very slowly. If I held the rear microswitch in long enough it would move enough to disengage the front microswitch. I have managed to get a couple of drops of oil onto it's pivot point and now it's moving freely, disengaging properly. So that appears to have solved the auto thread problem.

But having now actually managed to load a film into the machine I have a problem with the take up spool. I am suspecting a cracked nylon gear - I can hear a regular ticking sound from that region. When the spool turns with no film it seems to have enough motemtum to keep turning, but when running more slowly with film, it will turn for a moment and then stop. Do I really have to remove the transformer to get that motor out to see the gears? The plate it is fixed to seems just too big to clear the transformer. Any advice here welcome.

Next problem - no magetic sound.... Luckily I have a few optical sound films also, and these produce loud clear audio. Nothing from a known good magnetic film though. The head presser assembly is engaging correctly, so I can rule that out.

The Mag/Opt switch is working Ok as it does turn the exciter lamp off in magnetic mode.

[Thomas Knappstein]

Hi Clive!
To your Problem with the take up Motor gear. Remove the back Cover first. Then put the Machine on his Face and drop a big Rubber between the Front Cover and the Table where it will lie on. This is importand for the Focus Knob. There don´t get any pressure on this Knob.
After this you can unscrew the four Screws of the Transformer with a magnetic Screwdriver, so the Screws don´t fall into the machine. Now you are able to move the Transformer to the left Side a little bit. If you have done this you can unscrew the Take up Motor Gearblock and take it out of the Machine. Unscrew the little Board for the Wires too and desolder the blue and red Motorwire from this Board. Now you can take this Motor out and repair it.

[Clive Carmock]

Hi Thomas this was really useful and helped thank you for the advice. I have managed to remove the take up motor by losening the transformer as you mentioned.

The fault is, as expected, a cracked plastic gear. It is the smallest of the gears on the shaft with two gears to the side of the motor. I see Wittner in Germany still has these in brass so have ordered from there. Hopefully it won't take too long to arrive and I can at least get this part repaired. After ordering I notice they became unavailable on the website. I do hope they can manufacture another batch of these, since they seem to be a common failure. One of my non Xenon machines needed this part replaced on it's feed arm a couple of years ago.

My next fault on this machine is no magnet sound playback. However I think I will leave that until the take up gear is replaced and the motor secured back in place.

[Joel Bleakley]

Hello Clive, Good luck with the faults. I only just discovered this thread. Interestingly I've just performed the exact repair you mention on the take-up and supply reels on my xenon machine I just got of Jason Smith. I got my replacements from Van Eck. It must be the season for this type of repair Ha Ha! Well done too finding the Auto Release fault. For the gears I found you didn't have to completely remove the screws for the transformer if that helps. Just enough to give you the desired wiggle room. This is also a handy way of achieving your goal without dropping screws down into the machine.

[Clive Carmock]

Hi Joel, Ah good to hear van Eck will has these gears in stock, as it looks like I bought the last one Wittner had. The Wittner gear is made completely from brass. I had used a Wittner brass one a few years ago on my non Xenon maxhine in it's rewind area.

You are right I found just loosening the screws on the transformer was enough to move it enough to get the take-up motor out.

The auto-thread fault was interesting. The date code on the motors in my Xenon machine suggest it was made sometime in 1989 or just after. My older non Xenon machine has 1979 date codes. That one has never suffered any dried up grease - maybe better serviced by previous owners. The Xenon machine has grease that looked once to be white, that has gone to a light brown colour and started to get very sticky. I have been removing it and using a lithium based grease in it's place. The little metal lever that presses the auto-thread microswitch was very slow in moving and had clearly suffered from this dried up grease

I haven't tackled the Xenon machine's magnetic playback fault yet. That one bothers me. While I had to remove the amplifier module to replace the rear microswitch, I know I have replaced it correctly, having done this numerous times across the three machines I have.

It's not stuck in record mode - as none of the record LEDs are on. and it's certainly not erasing audio, as runnign a film that has been through it on another machine is fine. I guess using servisol or simialr contact cleaner on all the switches on the relay board might make sense.

I guess it is possible the head pressure pad isn't fully engaging. I can check when I get the take up working again.

I do notice the green plasic assembly that forms part of the pressure pad moves back quite slowly when going from forward to stop. So possibly some lubrication needed in that area, though not sure how much of the machine I'll need to disassemble to get to that from the inside.

[Clive Carmock]

A bit more on the repair of my GS1200 Xenon machine. The replacement gear arrived today from Wittner. Managed to fit it this morning and get the motor back into the machine. That's restored the take up reel to full working order. Take up tension seems a tad weak so might revisit this in the near future. I did put a tiny drop of oil on the bearings of the take up motor and gear shafts and ensured that the washers were all in the correct place as per the service manual when reassembling

Next I removed the amplifier again and used Servisol 10 contact cleaner on the two long record switches and all the volume & tone controls. I didn't separate the two amplifier boards as that means pulling off the vinyl covering from the rear plate, but I did manage to get the contact cleaner into the switches without.

After reassmbly I operated the record buttons many times to work the contact cleaner into those switches.

When testing after all this work, I am pleased to say the machine now replays magnetic soundtracks perfectly again.

The auto thread mechansim still disengages correctly, so the lubrication of the plate that operates the auto thread control has fixed that issue.

Certainly for the moment, this seems to have cleared the faults on this machine.