rotary switch with pot  - Page 1
Forum section: electronics / repair

author: croyleje
author_rank: Regular Contributor
timestamp: August 25, 2014, 11:49:01 pm
content: hello everyone i am working on a Lambda Power Supply i picked up and need a new voltage section switch. the switch has a rotary voltage selection switch on the outside knob and the inter knob is a pot for fine adjustment (see pic. attached) does anyone know were i can find one of these? ive looked online with no luck any help would be great. if not i am just planning on replacing it with a rotary switch then drilling a new hole for a pot.Jason

author: German_EE
author_rank: Super Contributor
timestamp: August 26, 2014, 07:13:05 am
content: I came across the same problem a year or so ago when I was repairing a ham radio transceiver, there is a solution but you will need to hunt for some parts:1) Find a rotary switch that has the correct number of poles and connections, the switch should be of the 'open frame' type.2) Disassemble the switch and remove the shaft. In my case the shaft was 6mm but yours will probably be a quarter inch.3) Replace the shaft with a short length of aluminum or brass tube then reassemble the switch. A certain amount of mechanical ingenuity is required here and every situation is different, in my case the main problem was filing away the shaft to fit the C clip without weakening it too much.4) Obtain a potentiometer of the right value but with a 4mm shaft. The shaft will probably fit down the tube used on the switch but if it doesn't then it is easy to drill out.5) Assemble using custom bracket that holds the rotary switch and the potentiometer behind it.All of this work took me three days but it was worth it because the switch/potentiometer was unavailable and I needed to get back on air.

author: coppice
author_rank: Super Contributor
timestamp: August 26, 2014, 07:32:21 am
content: There used to be a lot of these types of device around. Catalogues from switch and pot makers used to have numerous combinations, but the market for them largely evaporated. A source of NOS, or another supply with a different fault might be your best bet. How badly damaged is the switch? Is it beyond salvation?

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: August 26, 2014, 07:46:17 am
content: You did not specify the pot, so this might or might not work for you.BE-03-002 - Rotary Switch; 5 way, 2 pole (+ 47k Lin Pot)http://www.audiomaintenance.com/acatalog/Concentric_Switches.html

author: German_EE
author_rank: Super Contributor
timestamp: August 26, 2014, 12:42:20 pm
content: http://www.audiomaintenance.com/acatalog/Elma_spec2_200.jpgThis is what I made using the aluminum tube but they charge 36 GBP for it, it depends on how much your time is worth.

author: croyleje
author_rank: Regular Contributor
timestamp: August 26, 2014, 09:17:29 pm
content: the damage is mostly to the shafts something most have hit the shaft pretty hard and bent it so it is extremely hard to turn the range switch and at the higher ranges the contacts dont make contact. the pot is 50K so the link that was provided would probably work i really appreciate all the help and ideas. thanks Jasonps was thinking about taking it apart and trying to straighten the shafts but i think i like the idea of just replacing the shafts.

author: sacherjj
author_rank: Frequent Contributor
timestamp: August 26, 2014, 09:21:18 pm
content: It might be possible to center drill and tap the shaft and turn a piece to thread into to. Join with red lock-tite and voila. If you have access to a metal lathe, that is.

author: croyleje
author_rank: Regular Contributor
timestamp: August 26, 2014, 09:22:21 pm
content: almost forgot how about knobs to fit this type of set up meaning a knob with a hole in the middle any ideas?Jason