Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Use a Pencil Rubber to Clean Unglazed Ceramic




 
The AM Forum
May 27, 2018, 05:41:07 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Use a Pencil Rubber to Clean Unglazed Ceramic  (Read 9180 times)
0 Members and 1 Guest are viewing this topic.
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10062



« on: July 07, 2010, 03:14:27 AM »

I just finished rebuilding a multi-section ceramic rotary switch for the antenna tuner project.  I disassembled several switches that had identical 10-position ceramic rotary wafers and combined the hardware to form a 5-gang rotary switch by combining wafers onto one frame assembly and modifying the end bearing of another switch so that the shafts of the two switches can be ganged together.

The ceramic insulation used for the wafers as well as the insulated rotary shaft are made with unglazed porcelain.  After reassembling the modified switch, I noticed metal deposits all over the ceramic.  It seems that even lightly brushing nickel plated brass across unglazed ceramic leaves a metallic deposit, kind of like a pencil leaves a graphite deposit.  Part of the disassembly and re-assembly involved slipping brass sleeves over the ceramic rods and fastening the parts together with metal screws and bolts, so multiple metallic deposits ended up on the insulation between contacts that will be switching high voltage rf.

I was concerned about possible breakdown due to the metallic leakage path between HV contacts. If an arc occurred, it would likely leave carbon tracks impregnated in the ceramic, something I have found to be totally impossible to remove.  I have seen carbon tracks render tube sockets, HV standoffs and  feed-throughs, and ceramic switches useless.  I tried several different solvents and cleaners, as well as plain old soap and water, but nothing seemed to touch the contamination.

Then I tried "erasing" the metallic marks using the rubber on a #2 wooden pencil, and found that this removes them completely, along with the finger smudges left behind from handling the ceramic during assembly.  I carefully cleaned the entire switch assembly using this method and now the ceramic pieces look sparkling clean like they had just come from the  factory.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
WA1GFZ
Member

Offline Offline

Posts: 11152



« Reply #1 on: August 11, 2010, 08:23:06 AM »

Send the XYL shopping and run it through the dish washer
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.032 seconds with 18 queries.