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Gents Master clock wiring

JFisher

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Aug 1, 2016
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Hello All,

I am new to electric master clocks, and am attempting to get a Gents C7 working. I hope you won't mind some seemingly simple questions..?

I have just put a replacement magnet onto the slave dial movement which is set into the case, as the original magnet wasn't working. Both impulse arm magnets and the slave magnets now seem to function independently, but I can't get the lot working as a whole.

Firstly, there are 4 main terminals on the right hand inside of the case, most of the photos I've seen online have only two or three. These are labelled from 1 - 4 (top to bottom). Connecting 1 and 2 to a power supply seems to cause the main impulse lever magnets to work, but the slave does nothing. There is an extra switch on mine which is where the switch to the impulse magnets is, this closes just before the other, and I assume sends current to the slaves. Is this unusual? and what are the 4 main terminals for?? ie..which ones should the power input be connected to?

The slave is also fitted with a second fibre wheel and switch which closes and opens once a minute - just wondered what that is for?

Sorry if this is vague, if I can be prompted by someone as to what info you need, I will try to be more specific. Photos to follow also.

Many thanks,
Jason
 

JFisher

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Aug 1, 2016
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Some photos, Showing the whole movement, the 4 main terminals, and the additional switch in front of the usual impulse arm contacts.

Hope they work OK,
Jason

308257.jpg

308258.jpg

308259.jpg
 

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rogerj

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Dec 21, 2014
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An interesting variation on the bog standard C7. I see a selenium rectifier and possibly smoothing components at the top of the case. perhaps set up by Gents to run off a low voltage transformer (AC) Are you able to trace out the wiring of this section (rectifier, capacitors and inductors at the top) Unfortunately I'm going away for a few days and won't be able to follow progress until next week. Someone must know what's up...Roger
 

Tinker Dwight

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Oct 11, 2010
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Contacts 3 and for appear to be for recorders.
See:

https://mb.nawcc.org/showthread.php?32897

post #68 schematic.
That would explain the extra contacts, extra terminal and rectifier.
Your picture shows an extra wire dangling from the front?
There is something in the lower left that looks like a switch, What is that?
Now, I saw another clock. I believe that is the adjustable 200 Ohm resistor,
not a switch.
You may want to check the where the wires from you internal slave clock
goes.
My guess is that there is suppose to be a jumper between 2 and 3.
Also, you might check the variable resistance setting. It looks to be
set at the minimum end. This may be the reason it wiped out the coil in
the slave. I believe the resistor should be set closer to maximum.
Tinker Dwight
 
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JFisher

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Aug 1, 2016
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Thanks for your replies - Yes, I think the extra switch on the pilot dial is for running recorders or something similar, which require minute pulses.

I am trying various power sources, all 12V dc or less, with varying amps, but have tried nothing more than 600MA so far. I am struggling to understand why the main resetting magnets are operating (although only with the variable resistor set at a minimum as you note) but the pilot slave is not getting any power.... I had thought they were part of the same circuit. If this unit has been set up slightly differently, for whatever reason, some pointers would be helpful to eliminate all the unnecessary 'add-ons' so that I can use it as a simple unit to run a couple of slaves at most.

Thanks guys
Jason
 

Tinker Dwight

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Oct 11, 2010
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I'm looking at the photos.
I only see 3 wires coming from the dial.
Unless I'm mistaken, one goes to the some part of the
switch and the other two look to go the terminals 3 and 4.
These have the rectifier wired across them, as you'd see
in the diagram I'd pointed to. There are similar parts of the
diagrams. I can see two capacitors and two resistor spools
at the top of your clock.
Your running should be 200 ma so 600 ma sounds high.
For the slave, with only three wires, only one is connected to
the clock. I don't see terminals 3 connected to the rest of the clock
as in the diagram from the post.
Something is different but I'm not sure where.
It would be good if you could show a picture of the wires at your
slave dial and use an ohm meter to trace where the three wires
are attached in the main case.
From that I think we can figure out the circuit. I'm guessing that
they reduce the number of terminal contacts at some point, varying
from the diagram. I suspect that terminal 3 or 4 is common to the
contacts on the slave and the third it the power lead.
Ohmming it out will help to make sense.
Tinker Dwight
 

JFisher

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Aug 1, 2016
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I will try to trace the wiring tomorrow... shame they didn't use different colours!

For now... here is a photo of the slave dial movement and its wires. Yes, there are only three coming from the slave, two of the terminals from the dial having a common wire.

Thanks Tinker,

Jason

308333.jpg
 

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JFisher

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Aug 1, 2016
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I have had a little look at the clock again this morning. Two of the three wires from the internal slave go to the main terminals 3 and 4, with a rectifier wired across them. The third wire is connected to a) the small switch and then to both main terminal No. 1 and the large resetting switch and circuit (large magnets etc)... then back to terminal No. 2 via the variable resistor.

My electrical knowledge is not good enough to work out what is going on. I suspect that there is a fairly simple solution by bypassing some of the unnecessary components, I just don't know which ones. Could someone tell me what the job of the capacitors (two green boxes at top of clock case) and the two coils associated with them (resistors??) actually is in this circuit??
Thanks again,
Jason
 

JFisher

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Aug 1, 2016
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I'm sorry for this really basic wiring diagram, and my lack of knowledge of how to draw one properly, but below is what I can deduce from looking at the clock and testing the continuity of the wires etc... I hope it makes enough sense to be understood and maybe someone would be able to suggest what best to do next...

Many thanks,
Jason
308437.jpg
 

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Tinker Dwight

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Oct 11, 2010
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Great drawing. Again, look at the schematic on the page I posted.
The only difference I see is that there is an additional 3 ohm resistor
on the recorder contacts.
The capacitors are spark suppressors. The small coils are the 3 ohm
resistors.
The next question is the resistance of the coil you have on the dial.
In the schematic, it shows coils with 900 or 2500 ohms. These are not
like the regular slave coils that would normally be about 7.5 ohms.
it is designed to be used in Parallel and not in Series.
instead of running at 200ma, it was intended to run at about 20-25ma.
This was the reason the slave coil wasn't working. The voltage you
were using was too low. The original coil was suppose to run at 24 or
48 volts, depending on the resistance ( do you still have the original coil? )
You have two options as I see it. Either go back to the original coil on
the dial and use the proper voltage or rewire such that the dial is treated
like a slave.
What would you like to do? ( I hope you saved the original dial coil )
Tinker Dwight
 
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JFisher

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Aug 1, 2016
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This is so helpful, thank you! I was thinking along similar lines, and it makes perfect sense that the original slave magnet was not receiving enough voltage. I have kept it, of course, but I think the ideal thing would be to rewire it so that the slave dial works with it's new, 'normal' magnet, if this is possible.

Jason
 

Tinker Dwight

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Oct 11, 2010
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Calif. USA
If you want to bring it back to original, you need to get
the voltage that matches the coil you took off and connect
terminal 2 and 3 on the blocks on the case.
If you want to run a slave coil, you have to get a 50 ohm 5W
resistor and place it between 2 and 3 instead of a jumper.
The 50 ohm is for the 12V source you are using.
Tinker Dwight
 
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Tinker Dwight

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Oct 11, 2010
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Oops Edit
( Edited remove : An alternate way to avoid the resistor is to take the
jumper off the inside terminal #1 and put it on terminal
#3 of the inside block. )
( new instructions )

Add a jumper from terminal #3 to #4 to short the second contacts.

Remove the power lead from the case terminal #1 and connect
it to terminal #3 of the case terminals.
This puts the slave in series with the reset coil and shorts out
the second unused contacts.
Make a note on your schematic, and copy the original schematic,
I pointed to, onto a print out. Put the old coil and the new and old
schematics into a bag to keep in the bottom corner of the case.
When you pass on the next fellow will want to know what and
why it was wired as it is.
Tinker Dwight
 
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Hans Vrolijk

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Jan 7, 2005
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Jason,
Probably your C7 once drove recorders in a factory to measure the activity of e.g. weaving machines. That's the reason of the contact in the dial. I had such a clock and the dial coil needed 40 VDC to be activated ! attachment.jpg
 

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Tinker Dwight

Registered User
Oct 11, 2010
13,666
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Calif. USA
Jason,
Probably your C7 once drove recorders in a factory to measure the activity of e.g. weaving machines. That's the reason of the contact in the dial. I had such a clock and the dial coil needed 40 VDC to be activated !


attachment.jpg
He has put a serial wired coil in it rather than a 40V coil. He just needs to figure
how to get it to run. My last set of instructions should work fine. It is just adding
a jumper and connecting the power to 2 & 3 instead of 1 & 2.
Tinker Dwight
 

JFisher

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Aug 1, 2016
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After following Tinker's instructions, the clock is now working! I have drawn a neater wiring diagram (herewith, for any who may find it useful in the future) and also annotated a copy with the changes for anyone wanting to put it back to its original state. At the moment it will work with a 12V 600 ma supply, but only just. The variable resistor is set at a minimum, if any more resistance is added, then nothing happens. As it is, the re-setting magnets are working ok, the slave dial magnet is weak, and I have had to slacken off the return spring to get it to work. As I would like to run possibly one or two more slaves off this unit, I suspect something needs increasing... but would be, again, grateful for any help!

Many thanks,
Jason

308677.jpg
 

Attachments

Tinker Dwight

Registered User
Oct 11, 2010
13,666
72
0
Calif. USA
If you can't find another 24V supply easily you can use
another 12V in series.
Or, you can go back to the 50 Ohm resistor and parallel that I first
mentioned. The slaves don't require as much voltage as the
reset coil for the pendulum.
If you get an adjustable taped 50 Ohm resistor, you can easily
have a string of 3 or 4 movements.
There are a number of 50 Ohm rheostats on ebay of 25W and up
that would work fine.
Dwight
 
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