Macgregor Codamac

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Dodgy Geezer
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Macgregor Codamac

Post by Dodgy Geezer »

I'm putting a Macgregor Codamac back into working order, and I'm having trouble identifying a capacitor. Here's a pic - you can see why it's a candidate for replacing. It's the blue one next to the pot at the top right.

Having got it out, one of the end wires fell off, so it was obviously open circuit and couldn't be tested. Looking at the markings, I see the following:

4/
10V

The 4/ does indeed look like a slash, and not a poor 7. There are no other markings. Has anyone any idea what it might be?
dodgycap.jpg
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F2B
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Re: Macgregor Codamac

Post by F2B »

Yes, that is an electrolytic capacitor, 4.7 or 47 µF/ 10 Volts
Looking at the sheer size of the thing I'd say 4,7 ....
Should be available still...
F2B or not to be....
Dodgy Geezer
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Joined: 17 Jun 2018, 09:54

Re: Macgregor Codamac

Post by Dodgy Geezer »

I hear the 4, but I can't see the 7. It looks much more like a 4/

I enclose a pic of the offending cap, and a pic of the markings on the only other similar cap on the board. They seem to have an odd way of marking value...
The 4/ is the lower pic you can see why I don't think it says 4.7...
other cap.jpg
betterpic.jpg
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F2B
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Re: Macgregor Codamac

Post by F2B »

0.64 seems an odd value to me as well.
640nF... The usual steps are 560 > 680
There should be someone with the diagram around this place.
Let's wait and see... :roll:
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Dodgy Geezer
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Re: Macgregor Codamac

Post by Dodgy Geezer »

...and perhaps it's a 0.47uf. How would I tell?
Dodgy Geezer
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Joined: 17 Jun 2018, 09:54

Re: Macgregor Codamac

Post by Dodgy Geezer »

Remember this is from a 1960 tranny. I suspect that it's some old form of cap marking. if no one knows, the only thing to do might be to reverse-engineer the circuit and work it out that way :(

Unless anyone has a circuit diagram for a Codamac?
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F2B
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Location: 20 m NE of Amsterdam

Re: Macgregor Codamac

Post by F2B »

I'd second Phil's suggestion without a blink.
Phil has designed a wonderful encoder that makes a codamac go like it was supposed to.
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Dodgy Geezer
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Re: Macgregor Codamac

Post by Dodgy Geezer »

All interesting comments - but does that mean that no one knows what a marking of 4/ means on a cap?
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Phil_G
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Re: Macgregor Codamac

Post by Phil_G »

Codamacs were an abomination, put it out of its misery and gigerise it Dodgy!
I cringe when I see those wipers. Why????? what was Wee MacGregor thinking???

That cap isnt critical, its only the keying rate in conjunction with the preset, codamacs
were so inaccurate and drifty that I suspect they were SOT anyway. I can understand
everyone saying its a 7 as 4.7 etc is a standard E6 (and upwards) value, but its not unusual
to see non-standard values in timing specific stuff like the coder in the codamac.

i would try a 4.7μF tant and check the keying speed, if it cant be adjusted to suit the actuator
then up-it or down-it to suit. Check the quick-blip too, though thats less critical.

Honestly Dodgy I wouldnt worry. It looks as though its only the quick-blip pulser speed, just try a few near-values and test. I'm not aware of a circuit diagram in circulation, it would be nice to have :D

codamac_presets.jpg
Dodgy Geezer
Posts: 62
Joined: 17 Jun 2018, 09:54

Re: Macgregor Codamac

Post by Dodgy Geezer »

Well, Phil, how could I ever doubt you! 4,7uf works a treat.

Now for the difficult bit - trying to make it work with a Kinematic.....
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