8mm Forum: GS1200 main motor stopped

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Topic: GS1200 main motor stopped

Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 13, 2013 12:33 PM

Hi

Can anyone give me some tips at what to look at with a fault GS1200? I have two but my non Xenon unit has stopped working. There is no movement in the main motor. It won't run forwards or reverse. I think the motor itself is ok, with the fault elsewhere. When set to run the motor is getting around 1.2 V clearly not enough to drive it!

Can anyone give me any pointers into what component might have failed and causing this?

The ESS switch is set to normal

Regards
Clive

[ January 13, 2013, 01:43 PM: Message edited by: Clive Carmock ]

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Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 13, 2013 03:25 PM

As a followup to my post. I followed the "Main motor doesn't run" procedure in the Service manual, page 91.

Following the Japanese translation sometimes create ambiguity, anyway this is what I did.

Voltage between Pins 3 & 7 of IC451 on the small motor control board was 12V. Then between 3 & 4 was actually 11V not 1 V as shown in the flowchart. SO maybe my IC451 is faulty, but the next steps check out Ok, so I continued....

I shorted out the E-C terminals of TR 453 - nothing. Then the next step is shorting out E-C terminals on TR 452, then doing this the motor DID run, but ran fast.

I don't know enough about how this circuit works to determine if fast running is to be expected if this transistor is shorted like this. However the troubleshooting guide indicates in this situation TR452 is faulty. The circuit diagramme shows it is a 2SA720

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Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 16, 2013 05:04 PM

A little more on this.

Today I replaced the suspect faulty transistor on the motor control board - TR452.

The good news is this made the main motor run again. The bad news is as it was running after a period I heard a cracking noise from that area of the machine and then the left hand of the two vertical fuses on the transformer board blew.

The service manual isn't so helpful in this area. I am suspecting the downstream transistor TR451....

Any advice appreciated.

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Hugh Thompson Scott
Film God

Posts: 3063
From: Gt. Clifton,Cumbria,England
Registered: Jan 2012

posted January 16, 2013 05:29 PM

Clive, I will give my little bit of advice,and it's very sound,get in
touch with Mr Bill Parsons who is a member of this forum, and
I'm sure he will be able to repair it for you.Good luck.

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Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 16, 2013 07:12 PM

Thansk Hugh - I have dropped Bill a message. Hopefully I can get this machien back into action. Everything else about it is in good condition, just the motor circuit.

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