8mm Forum: Goko RM-5000 speed help?!

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Topic: Goko RM-5000 speed help?!

Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 27, 2018 11:48 AM

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My trusty but slightly negleted Goko RM-5000 recording editor (which I have used many times over the years for very reliable re-recording) has developed a fault.

Firstly, although the main motor was turning and driving the main belt to the main drive shaft which in turn runs everything else, the main drive shaft was stiff and refusing to turn correctly.

After dismantling and careful application of WD-40, the main drive has freed and is turning fine.

But now the speed is running far to fast, at about 30 fps plus! Altering the setting of the 18fps / 24fps and the + / - speed adjust does adjust the speed, but basically it is running radically too fast?!

Maybe the WD-40 has penetrated somewhere it shouldn't?

Or maybe I've damaged a speed control board opening it up?

Any help appreciated. [Roll Eyes]

[Roll Eyes]

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Nantawat Kittiwarakul
Master Film Handler

Posts: 280
From: Rajburana, Bangkok, Thailand
Registered: Aug 2017

posted June 27, 2018 08:42 PM

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It's very likely that there're another potentiometers for speed regulation INSIDE the unit,at the power board. That's all it need to re-calibrate the speed. [Big Grin]

[Big Grin]

The picture of its innards will speak for itself.

--------------------
Just a lone collector from a faraway land...

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Gilbert Lambert
Expert Film Handler

Posts: 184
From: Ostende, Belgium
Registered: May 2016

posted June 28, 2018 01:40 AM

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It's an easy fix Rob , try to locate the potentiometers , I've done this many times with this type of viewers.

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 28, 2018 04:18 AM

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Thanks Guys, although I've removed the back cover again and set the potentiometers to the lowest speed setting.

Still it is running at an increadibly high speed.

Hmm...

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Gilbert Lambert
Expert Film Handler

Posts: 184
From: Ostende, Belgium
Registered: May 2016

posted June 28, 2018 05:15 AM

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If the potentiometer works Rob , when you adjust it whilst the viewer is running with sound film you can hear it at the sound it's slowing down , normally it's not so easy to get it at exact 24 frames per second , it's the first time I hear about a potentiometer not working , I had at least 10 of those in my hands the past years... In this case I don't know ... ( I never had to replace a faulty potentiometer ...)

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 28, 2018 05:20 AM

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Hi Gilbert.

The potentiometers for 18 fps and 24 fps are working in that they will slow down or speed up the motor.

And the 18 fps / 24 fps switch works also.

But everything is running at a massively increased speed.

It's a strange one.

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Heinrich Kronschlaeger
Film Handler

Posts: 39
From: Linz, Austria
Registered: Jan 2004

posted June 29, 2018 03:02 AM

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Hi Rob,
I own several of the similar viewers Goko 8008 and Erno 904 ( stereo ). At one of them I had the same fault. The machine always turned slower and slower. But trying to turn the axis with the power of the motor, any electronic component on the MOTOR BOARD broke ( IC or others ). I discovered that the long axis of the flywheel could only be turned with force. I disassembled this small wheel and oiled the axis ( sintered bearing oil ). It would have been better to oil the axis immediately.
Later the motor ran more quickly,but at high speed like your Goko 5000.
I don`t know how to change the electronic components at the motor board. So now I use this Goko 8008 with an external power supply ( changable volts ). For switching the DC power on and off, I installed a switch on the Goko . The sound of this Goko 8008 is perfect.

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 29, 2018 04:51 AM

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Thanks Heinrich, I think you are right. It looks like there must have been some damage to the electrical components that control the motor speed.

With no repair specialists around any more, it looks like another piece of nice super 8 equipment resigned to nostalgia.

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted June 29, 2018 05:27 AM

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I used to work on a lot of regulator boards. Here and there an operational amplifier IC output would stick high and the circuit would go out of control.

-what was bad is these were controlling a High Voltage power supply output and after that things got nasty!

Rob, do you have the manual and if so does the manual have a schematic?

If I saw it I could at least make a guess what to change and help you source the part. (It's pretty amazing how many old electronic parts are still findable.)

-after that it would just come down to finding somebody who is skilled at soldering.

--------------------
All I ask is a wide screen and a projector to light her by...

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Heinrich Kronschlaeger
Film Handler

Posts: 39
From: Linz, Austria
Registered: Jan 2004

posted June 29, 2018 09:01 AM

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About the schematic of the Goko sound viewer:
https://www.filmshooting.com/scripts/forum/viewtopic.php?f=1&t=3274&p=24219&hilit=Goko+RM+8008#p24219
Maurizio Di Cintio wrote in this thread:
*************************************************************
As for sound circuit scheme, I got in touch with Sansei Koki in Japan in 1996 to enquire about this and other issues and they told me they had no spares or diagrams and even the engineer who had designed the RM 8008 no longer worked for them, nor did they have any piece of news thereabouts (!!!!).
*************************************************************
I think the Goko 8008 ( Stereo ) and the similar 5000 ( Mono ) was designed from the same engineer.

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 29, 2018 09:05 AM

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Thanks Steve. I do have a copy of the user manual but unfortunately there are no schematics in there.

Maybe someone here has the workshop manual?

If so, and we can get Steve's knowledge behind it, the poor old Goko may still have a fighting chance.

It would be an awful shame to give up on it - recordings from it were always spectacular.

EDIT: Thanks Heinrich, I was typing my reply as you posted. The RM-5000 and RM-8008 are definitely from the same stable, as when you remove the front cover, all the gaps are there for the stereo VU meters, etc.

Not looking good on getting hold of a schematic then.

The dirty speed sensor is interesting though.

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted June 29, 2018 09:20 AM

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Yes, a speed sensor is definitely a good candidate: you can't regulate what you can't measure!

-and if all you had to go by was a speedometer, it would be perfectly understandable if you pressed the gas pedal to the floor if it died on you.

(Tell that to the Highway Patrol!)

--------------------
All I ask is a wide screen and a projector to light her by...

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Paul Browning
Phenomenal Film Handler

Posts: 1006
From: West Midlands United Kingdom
Registered: Aug 2011

posted June 29, 2018 10:28 AM

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Hi Rob, I have both these editors i'll take a look tonight for you and see if I can pinpoint perhaps what the wd has made fail, certainly an odd one. I did not know it had a speed sensor in there, so maybe its that gone wonky, but sounds like you have shorted something on the board, a regulator, is there residue of wd on the board anywhere that you can see?.

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Kevin Clark
Jedi Master Film Handler

Posts: 978
From: Bapchild, Kent, UK
Registered: May 2004

posted June 29, 2018 11:40 AM

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There is a small sensor (Hall's IC?) that counts the drive revolutions - it is quite flimsy and affected if it is moved too far from the small magnetic shaft it measures - you may have moved it away from the shaft during your service Rob - have a look and literally bend it back so it almost touches the shaft.

I don't have one of these any more or I would of course send you some guide pics.

Hope this helps, Kevin.

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 30, 2018 03:32 AM

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Hi Paul, I was very careful with the WD-40 but it is still possible some ended up where it shouldn't.

Kevin, I think I know exactly the part you mean and yes, it is very possible that I moved it. I shall take the front apart later today and try that.

EDIT: Yes! Kevin it was that sensor! I've moved it back and all is well!

Thanks to all you guys for your help. I'm soooo happy as I thought I'd really broken it.

What would we do without our friends here on the forum. [Smile]

[Smile]

[Smile]

[Smile]

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Paul Browning
Phenomenal Film Handler

Posts: 1006
From: West Midlands United Kingdom
Registered: Aug 2011

posted June 30, 2018 05:43 AM

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Hi Rob, glad you sorted it, I did take the back off mine last night and could see the circuit board behind the speaker, plenty on there, but I did not locate the sensor, is this visible from the front when parts are removed ?.

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted June 30, 2018 06:59 AM

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Yes Paul, with the front cover removed the sensor is just above the main motor drive. It is like a tiny prong that bends up and down (although not too many times I'd imagine!)

As soon as Kevin mention it I remembered moving it upward slightly to remove the main belt.

I even remember wondering what on earth it was. Doh!

So thanks to Kevin's marvelous advice, I bent it back down a couple of mm so that it almost touches the drive and hey presto!

Thanks again for everyone's help and special kudos to Kevin.

I'm so relieved it was such a straightforward fix.

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Kevin Clark
Jedi Master Film Handler

Posts: 978
From: Bapchild, Kent, UK
Registered: May 2004

posted June 30, 2018 06:55 PM

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Thank you for your kind comments Rob it's great to hear your Goko is now OK.

Kevin

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Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted July 04, 2018 09:51 AM

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I've been using the Goko on and off over the last week with flawless performance.

Again, I can't thank Kevin enough for his insight, but also just to add that this forum is such a great wealth of knowledge, experience and enthusiasm that it really keeps our valuable film equipment going.

What a great community, with great moderators, to be a part of. [Smile]

[Smile]

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