Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Fixed my own R-390A micro switch




 
The AM Forum
August 26, 2019, 01:37:06 AM *
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: Fixed my own R-390A micro switch  (Read 465 times)
0 Members and 1 Guest are viewing this topic.
W8ACR
Contributing
Member
*
Offline Offline

Posts: 627


Penta 254W


« on: April 23, 2019, 11:32:46 PM »

I have recently acquired a very nice Collins R-390A that would not turn off. As I understand it, the 26Z5W rectifier tubes were commonly replaced with solid state diodes, and this sometimes caused the contacts in the ON-OFF microswitch to weld together due to current inrush. Sure enough, I looked at the power supply subchassis, and there were two diodes, and no tubes. I took the diodes out and plugged in two 26Z5W tubes, and promptly blew the AC line fuse. I found out that one of the tube sockets was damaged and shorting to ground. I replaced both tube sockets, and plugged the tubes back in, and success! no more blown fuses. One problem fixed.

The receiver would still not turn off, and I figured I would have to find a suitable replacement switch. But as a last ditch effort, I thought I would try to repair the switch. I took off the front panel, and getting to the switch was relatively easy. The switch was designed so that it could be carefully pryed open, and just as I expected, the contacts were welded together. Using a jewelry screwdriver, I carefully and gently worked on separating the contacts. To my surprise, they actually separated and looked undamaged. I put everything back together, and all is well.

I just thought I would share this story in case someone out there may have a similar problem. I really did not think I would be able to repair the switch. and maybe I was just lucky. Better to be lucky than good. Grin

Ron W8ACR
Logged

The AM voice of Knox, North Dakota
WD8KDG
Member

Offline Offline

Posts: 250



« Reply #1 on: April 24, 2019, 12:16:52 PM »

Ron,

Somewhere in the past there has been another fix for what ails you. A resistor & cap are used to suppress the arc when those contacts open.

Might find it here: https://www.r-390a.net/

or: http://mailman.qth.net/pipermail/r-390/

Craig,
Logged

Ham radio is now like the surprise in a box of "Cracker-Jacks". There is a new source of RFI every day.
WBear2GCR
Member

Offline Offline

Posts: 3710


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #2 on: April 26, 2019, 11:04:43 AM »

I sent you a PM, Ron, there were a few switches on epay... also almost any suitably rated microswitch could be
subbed into that spot, would need a suitable physical dimension, but there are a lot to pick from.

glad you go it fixed - I had one that was really well fried in an R-392...
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
WD8KDG
Member

Offline Offline

Posts: 250



« Reply #3 on: April 26, 2019, 12:53:04 PM »

Found it in my notes:

Added a 0.01mF 1KV ceramic cap in series with a 220 ohm resistor across the function switch contacts. No welded contacts since.

Craig,
Logged

Ham radio is now like the surprise in a box of "Cracker-Jacks". There is a new source of RFI every day.
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 0.033 seconds with 18 queries.