UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 16th Nov 2020, 2:46 pm   #1
Chris Wilson
Heptode
 
Join Date: Nov 2011
Location: Whitchurch, Shropshire, UK.
Posts: 612
Default How does this vac variable capacitor adjust please?

I am familiar with vac variables that adjust value via a threaded rod that you turn to mesh and unmesh the plates, but I have seen one that I am unsure of the adjustment method.

It looks to me as if the rod was designed not to turn, but to be pulled out, perhaps using a cam as the rod also seems to have a ball or swivel joint inside the body to allow misalignment. Cam used to pull the rod? Motor drive using and external threaded rod and bushing? What might be the hollow tubular stub on the side of the body be for?

Can it be used with a conventional panel knob or panel turns counter? It's a 50 to 5000pF at 10kV Comet vac variable, anyone able to shine a light on the designed adjustment method and possibly an ideas as to its age? Part number is CV1A-5000E/10

Many thanks for any insight. I am looking for a 1000pF or greater vac variable, with an operating voltage of over well 5kV if anyone has anything that is, or can be, tested for breakdown. I have a suitable uA HV tester. I'm in north Shropshire.
Attached Thumbnails
Click image for larger version

Name:	1.jpg
Views:	257
Size:	35.2 KB
ID:	220472   Click image for larger version

Name:	2.jpg
Views:	227
Size:	26.5 KB
ID:	220473   Click image for larger version

Name:	3.jpg
Views:	243
Size:	33.8 KB
ID:	220474   Click image for larger version

Name:	4.jpg
Views:	188
Size:	34.4 KB
ID:	220475   Click image for larger version

Name:	5.jpg
Views:	192
Size:	41.9 KB
ID:	220476  

__________________
Best Regards,
CW. 2E0ILY
Chris Wilson is offline  
Old 16th Nov 2020, 10:26 pm   #2
trh01uk
Octode
 
trh01uk's Avatar
 
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,648
Default Re: How does this vac variable capacitor adjust please?

What about asking the company who make them: http://www.comet-pct.comwww.comet-pct.com?


Richard
trh01uk is online now  
Old 17th Nov 2020, 11:03 am   #3
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: How does this vac variable capacitor adjust please?

Quote:
Originally Posted by Chris Wilson View Post
Cam used to pull the rod? Motor drive using and external threaded rod and bushing? What might be the hollow tubular stub on the side of the body be for?
Thought the stub might be water cooling but not familiar with that sort of end-piece, and don't know what piece attaches to the existing arrangement. Water needs an 'in' and an 'out'. The Marconi H1140 10kW HF transmitter uses two vac caps in the pi-output stage, and both are rod-actuated. The rod is connected to a stirrup inside which a cam rotates, driven by a servo motor, and allowing the rod to move vertically as the cam pulls the stirrup.

Because of the vacuum, there's a hell of a lot of torque involved and chocks of wood are used when working on the servo drive so the cap doesn't thunk in and take your finger-ends with it.
__________________
Regds,

Russell W. B.
G4YLI.
russell_w_b is offline  
Old 17th Nov 2020, 11:58 am   #4
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,798
Default Re: How does this vac variable capacitor adjust please?

The pipe stub will be for forced air cooling of the bellows and of the floating capacitor electrode structure. THe fixed capacitor electrode structure is accessible for conduction cooling at the bottom end of the capacitor (it will be electrically hot, of course)

These things are for 100 to 1000Amps of current. Cooling is important. Water cooled ones can shift more heat but it's messy and two smaller pipe connections are needed.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 17th Nov 2020, 3:20 pm   #5
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: How does this vac variable capacitor adjust please?

Here's the drive arrangement of a 50-2300pF CV1C-2300FW/15 which looks similar to yours. You can see the shaft attached to the stirrup rising through the deck and the cam, gears and motor that drive it. The configuration (on this transmitter) doesn't use the collar and the cap is bolted directly to the deck.

There is no forced cooling.
Attached Thumbnails
Click image for larger version

Name:	motor.jpg
Views:	180
Size:	73.9 KB
ID:	220607  
__________________
Regds,

Russell W. B.
G4YLI.

Last edited by russell_w_b; 17th Nov 2020 at 3:25 pm.
russell_w_b is offline  
Old 17th Nov 2020, 11:21 pm   #6
M0AFJ, Tim
Hexode
 
M0AFJ, Tim's Avatar
 
Join Date: Mar 2006
Location: Helston, Cornwall, UK.
Posts: 301
Default Re: How does this vac variable capacitor adjust please?

What are you building?, it’s going to be impressive...
M0AFJ, Tim is offline  
Old 18th Nov 2020, 12:49 am   #7
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
Default Re: How does this vac variable capacitor adjust please?

RF induction heater? Welder?
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is online now  
Old 18th Nov 2020, 10:37 am   #8
GMB
Dekatron
 
GMB's Avatar
 
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,086
Default Re: How does this vac variable capacitor adjust please?

Odd that they do not have a standard product that goes to 5000pF so I presume that must be a custom part.

Looking at the pictures, I would say there is a bit missing - clearly it needs some kind of gland at the top which may be where the screw adjuster would be.

So maybe it has been taken out of something, so I wonder if it still works.
GMB is offline  
Old 18th Nov 2020, 12:25 pm   #9
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: How does this vac variable capacitor adjust please?

What you need is a smaller one of these. It can either sit on the end of your existing collar or right on the cap itself, depending on the length of threaded shaft you have. That said, I suspect your cap has a fixed drive-rod that can't be removed or modified so easily as your rod looks to go down into the cap itself and is secured differently. But it will convert your cap to a rotary-tuned one.

This is an EEV one, but Comet and Jennings ones are similar. As I recall, new caps come with them whether you need one or not.
Attached Thumbnails
Click image for larger version

Name:	collar_01.jpg
Views:	85
Size:	106.4 KB
ID:	220676   Click image for larger version

Name:	collar_02.jpg
Views:	87
Size:	109.6 KB
ID:	220677  
__________________
Regds,

Russell W. B.
G4YLI.
russell_w_b is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:11 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.