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Old 17th Aug 2019, 9:27 pm   #1
Montymoo
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Default Leitch Studio Clock Problem

Hello

I'm a new member and was hoping someone may be able to help me from the radio broadcasting world.
I have an analog Leitch Studio Clock (model MAC 5412) which has been working perfectly but now refuses to let me reset the hands to the correct time.
Following an attempt to adjust the time, the hour and minute hands have become offset to each other. For example, if the minute hand is on 12, the hour hand lies halfway between two hour positions so it looks like half past the hour and that difference remains as the clock sweeps.

It's used in a stand alone mode with no time code attached.

I have read the clock manual and tried correcting the time from the instructions provided but the clock immediately resets itself and continues with the problem.

Hoping you can advise.

Thanks.
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Old 18th Aug 2019, 8:38 am   #2
Mike Phelan
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Default Re: Leitch Studio Clock Problem

Hi and welcome,

So, how does the clock work - spring driven, quartz, synchronous motor? How do you adjust the time - moving the hands or a knob?
Can you move just the hour hand by itself?
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Old 18th Aug 2019, 10:10 am   #3
brunel
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Default Re: Leitch Studio Clock Problem

A bit of explanation here: https://mb.nawcc.org/threads/leitch-...ch-day.125441/

Or: https://www.imaginecommunications.co...d_20130312.pdf

Last edited by brunel; 18th Aug 2019 at 10:12 am. Reason: XTRA INFO.
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Old 18th Aug 2019, 8:04 pm   #4
MotorBikeLes
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Default Re: Leitch Studio Clock Problem

I know nothing about clocks, but a few common sense (I think) observations. Assuming it is similar to the one in Brunel's link, that electrolytic capacitor looks like the ones fitted in early 1970's hybrid Grundig TV sets, so change it. I would also run your soldering iron on every one of the leads of the ribbon cable It is easy to get difficult to spot dry joints.
There are three stepper motors shown, so with the clock disconnected from mains (after doing a reset, whatever that is), try with an AA cell with wires connected to find if you can get one of the steppers to move. Whichever one is not where the reset should have put it, step it thro until it is in correct position.
I have not done much with steppers, but I did find that by touching and removing on the correct pins it the correct order, you can make them go wherever you wish.
Cheers, Les.
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Old 18th Aug 2019, 9:44 pm   #5
Station X
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Default Re: Leitch Studio Clock Problem

I wonder how the stepper motors "home"? My only experience with stepper motors is with CNC machine tools. These home by simply driving the motor in one direction until the machine's slide contacts a limit switch. From then on the machine simply counts the pulses it sends to the stepper motor so it knows where the slide is. Some machines have shaft encoders so there's some feedback, but I've no experience of these.
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Old 22nd Aug 2019, 10:02 am   #6
red16v
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Default Re: Leitch Studio Clock Problem

We had dozens and dozens of the DAC model clocks around our broadcast station. But it was a long time ago and I can’t remember any detail, although we used to repair them but they were not very user serviceable. The two things I do remember is that the internal illumination ‘facility’ was not very long lived and we used to retrofit a home brew LED strip mod (these clocks were often used in control rooms with little illumination so internal lighting was essential. Secondly, I recall the stepper motors calibrated their physical position by means of aligning tiny holes in some of the cogs. If you take them apart ALL is lost and you will not be able to reassemble the motors correctly and the clock is then useless - in this event we would swap motors around from scrap units.

As an aside, twice a year when the UK clocks changed we had to wait until 2am for our Leitch satellite receiver system to change and then we had to go around the building and check every clock had changed. The clock can detect when its external time code feed has been interrupted, reset itself to the ‘all hands to 12’ position, then move the hour/minute hand to the correct positions plus one minute, them wait until the external time feed is ‘ticking’ over to the next minute then set the second hand going.

Sorry I can’t offer any more technical advice, it was so long ago now. Don’t take the stepper motors apart.

PS, are you sure the hand hasn’t simply moved on it’s shaft?
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Old 2nd Sep 2019, 9:16 pm   #7
Montymoo
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Default Re: Leitch Studio Clock Problem

Thanks for your detailed reply.

The clock originally would reset itself to "all hands to 12" and I could then set the correct the time without any problem and it's running smoothly for some years. Now after a regrettable attempt to fine tune the time it's really got it's knickers in a twist. The hands now reset themselves to something like 3 mins to 11 but even then, the hour and minute hand are properly aligned.

I have also tried and I'm not sure I should have done this, physically moving the pulley drive wheels inside to align the hans to midnight but soon as the power goes on they revert to their 3 mins to 11 position.

I shall endeavour to research this problem and I'll heed your advice about the stepper motors.

Thanks again.

PS I used to work as a Station Assistant at Radio Derby in my youth. The clocks then were GENT and were driven by a master Pendulum clock. We always had to check the time against the 'speaking clock' and tell the news readers if the clocks were plus or minus a few seconds so they didn't crash into the pips when joining network.
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Old 2nd Sep 2019, 9:24 pm   #8
Montymoo
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Default Re: Leitch Studio Clock Problem

Quote:
Originally Posted by Mike Phelan View Post
Hi and welcome,

So, how does the clock work - spring driven, quartz, synchronous motor? How do you adjust the time - moving the hands or a knob?
Can you move just the hour hand by itself?

Thanks for your reply.

It's driven by stepper motors which are in turn driven by Time Code or Mains Frequency or Internal oscillator.
Adjustment is made electronically and you can adjust each hand individually but the problem is the clock will then reverts to its 'offset' position.
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Old 2nd Sep 2019, 9:41 pm   #9
Montymoo
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Default Re: Leitch Studio Clock Problem

Thanks or your reply.

I've read the first thread link you posted and that has been of some help.

Although it's not strictly the same the clock, I've been using the manual detailed in the second link but unfortunately it does not describe how to get the hands aligned and back in sync. There is still a considerable offset between the hour and minute hand.
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Old 2nd Sep 2019, 9:47 pm   #10
Montymoo
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Default Re: Leitch Studio Clock Problem

Thanks Graham for your reply.
Yes I had a spell working for a company that made coordinate measuring machine which used 'inductosyn' to tell the steppers when to stop. I worked on the advertising side so never really got to grips with the engineering bit.
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