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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 15th Apr 2024, 1:50 pm   #1
Alan Bain
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Join Date: Jan 2012
Location: Heswall, Merseyside, UK
Posts: 192
Default Tek cam switches

I know many people have trouble with these... but have been fixing some 7A29 plugins and found one where a portion of the plastic cam has cracked off the shaft (input attenuator). The broken portion was recovered, but wondering if this is repairable with glue? Maybe a low viscosity epoxy? Has anyone got any experience of this?

It's also not clear what to use to lubricate them - electrolube do a special grease for plastic that I'm tempted to try. Unlubricated they get very stiff and look very likely to break themselves.

There is also one in the calibrator that keeps not opening when the cam moves away. I guess the spring tension is just too low. I know Tek made a cam switch repair kit for these, but I've only ever seen pictures (see attached). Is there a solution for the rest-of-us?
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Old 15th Apr 2024, 3:43 pm   #2
cmjones01
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Default Re: Tek cam switches

I've got a few 7A29 plugins and the cams do tend to crack and come away from the shaft. I fixed mine with epoxy (Loctite 3430 because it's what I had to hand, and I like it). They seem to keep working after that, but they don't get very intensive use here at the moment.

Chris
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Old 15th Apr 2024, 4:12 pm   #3
RogerEvans
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Join Date: Oct 2014
Location: Wiltshire, UK.
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Default Re: Tek cam switches

Regarding the switch in the calibrator that does not open -

1. Does it have some sticky contamination and just needs cleaning? The standard recipe is take a strip of paper about 2.5mm wide, soak one end in IPA, insert between the finger and the PCB with the switch open, close switch and remove the remove strip. Repeat as necessary. If you search hard enough you can find just what type of paper to use but it is not critical unless you get over vigourous and start removing the gold flashing.

2. There are many warnings not to do this so it is a last resort! Using something like a dental pick pull the end of the finger 1mm or so upwards, directly away from the PCB. If you overdo this then trying to bend the finger down again is probably not going to work! I have tried this twice, on a very battered 7T11 that was not working anyway! One worked fine, the other remained unreliable.

Roger
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Old 18th Apr 2024, 5:58 pm   #4
Alan Bain
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Join Date: Jan 2012
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Posts: 192
Default Re: Tek cam switches

I've tried the paper & IPA approach, think I'll have to try #2 very carefully! Anoying when it's a switch in the mainframe rather than a plugin where I can probably find some spares!

Alan
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