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-   -   CTC-5 Westcott VHF fine tuning/channel binding (http://www.videokarma.org/showthread.php?t=269037)

old_tv_nut 05-19-2017 01:10 PM

CTC-5 Westcott VHF fine tuning/channel binding
 
What should I use to remove the gunk and free up the shafts?

I mentioned this in another thread about modifying a Radio Shack modulator - moving it here to isolate the topic.

I finally got to unmounting the tuner and mounting it in the service position on the back of the chassis. Only disconnection needed is the IF input, and I hope not to have to disconnect soldered wires, so don't want to remove the tuner completely.

My loss of fine tuning was due to running the fine tuning dial cord off the pulleys - seems to be unbroken, maybe stretched - should be an easy fix. I'm happy to report that the concentric shaft and sleeve at the tuner are not binding or broken!

My problem is the concentric VHF channel shaft and VHF fine tuning sleeve up at the knobs are gunked up and binding to each other badly.

What should I use to remove the gunk and free up the shafts?

Keep in mind that if possible I want to do this in my living room and I don't want to remove the tuner to the garage to dunk it or something. I cannot move the whole set there myself either.

Over-all view of tuner in service mount
https://c1.staticflickr.com/5/4251/3...f2f1ba7d_b.jpg


Knob shafts that bind
https://c1.staticflickr.com/5/4220/3...d842a489_b.jpg


Tuner shafts on right do not bind
https://c1.staticflickr.com/5/4269/3...3e97b6a1_b.jpg

oldtvman 05-19-2017 01:35 PM

We used to use Blue Shower, but I don't think they make it anymore.

oldtvman 05-19-2017 01:36 PM

http://www.mcmelectronics.com/produc...0-10S-/20-2100

old_tv_nut 05-19-2017 01:39 PM

Thanks

old_tv_nut 05-27-2017 02:32 PM

Update:

I ordered a can of Blue Shower, then made sure my will was in order after reading all the warnings on the can!

The Blue Shower removed a lot of visible gunk, but didn't free up the mechanism (as expected apparently has no lubricating qualities). Application of oil with the mechanism held in a couple of different positions to get it to run into various places did the trick.

Had to restring the fine tuning pulleys (original problem with loss of fine tuning action). Unfortunately, I managed to pull the string loop on one end out of the teensy brass ferrule that crimps the loop. I managed to reopen the ferrule with a needle and jeweler's screwdriver, but couldn't get it to crimp down again well enough. So, I made a loop with a double knot, and restrung everything. This turned out to be easier than I expected (never did one before), but of course the string is now slightly shorter, so it's wrapped onto the tuner-end pulley (where the end loops are) a bit peculiarly - but it works. It's got a tiny bit of slack, but not enough to run off the pulleys, and I'm hoping it won't stretch in the future.

One thing I will have to go back on - in partially disassembling the gearing, I slipped the VHF channel selector a cog and it now indicates one channel off - 3 shows as 4, UHF shows as 2, etc.

bluenorm 05-27-2017 03:04 PM

brake cleaner, paint thinner, control and contact cleaner, to mentioned 3 products

wkand 05-27-2017 04:23 PM

Cleaning RCA tuner
 
What's the story with WD-40 and tuner / control cleaning? Some say it works (it definitely de-gunk's mechanical assemblies like this and lubricates). Is there a concern about the phenolic or other plastic like parts deteriorating? I have successfully used it for label removing on plastic containers, like the shredded parmesan cheese containers (recycle #1) from Costco. I also used it on a barbeque gas control that was frozen. Got 3 more years out of that grill.

As far as doing this in your living room, should be fine as long as there is ventilation (maybe use a fan nearby?), and a tarp or old towel under where you are spraying to catch overspray.

Electronic M 05-28-2017 01:55 AM

Wayne, not sure if the design of the CTC-5 tuner allows it, but if I'm not sure I can get a dial cord taught enough I'll often add a spring at one of the anchor points to take up the slack.

I've had WD-40 work fine as control and tuner cleaner. Some hate the practice and are scared to death of it. I'm sure there are some risks of damaging wafers. It is one of those things I don't like to do when I have a can of the right stuff on hand, but if lube is needed or I'm in a pinch and don't have proper cleaner I'll use it.

Pencil erasers make good contact cleaners...Especially the white, soft drafting erasers....Even when I have the right cleaner I often use those as scrubbing pads, and they do a good job of removing the tarnish that the cleaner softens/polishing the metal.

old_tv_nut 05-28-2017 10:54 AM

If you look at the 3rd pic, you can see the tuner-end pulley. It has a wide slot (hidden behind the shaft) that the string enters after wrapping around at least a half turn, and then the string has a loop that hooks onto a tab. Both ends of the string have the same sort of loop, but you can see I managed to pull one loop open. There's no evidence of a tensioning spring I can see, but adding a small one might be a good idea.

So, the string path is:
End loop on tuner pulley, small pulley, knob pulley (multiple friction wraps), second small pulley, second end loop on tuner pulley.


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