Unusual problem? Mains switch... - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 8th May 2018, 4:32 pm

On old gear it's quite normal for the lubricant in on/off switches to dry out to the point where it totally gums-up the switch action: this applies both to the rotary built-into-volume-control kind of switches and on/off toggle-switches.

A good blast with switch-cleaner (in the past servicemen would have used Carbon Tetrachloride but that's been banned for decades) and a few cycles of turning-on-and-off, followed by a squib of Electrolube will usually fix the problem.

kestrelmusic · 9th May 2018, 8:08 pm

Quote:

Originally Posted by G0HFCFrank

Why fit a double pole switch at all? It has been standard practice for some years now to only switch the live side of the mains.

It's rather curious mains/battery wiring - the filaments are in series and take their supply via a 1680 ohm resistance from the HT reservoir cap. One pole of the mains switch disconnects the mains neutral which is wired direct to chassis; the other pole disconnects the battery LT positive from the filament chain.

I was lucky - I managed to prise the switch away from the back of the pot and, with the aid of a drop of Servisol got it going again.

Voxophone · 10th May 2018, 4:57 pm

I've had this problem a few times recently. Someone on here suggested flooding the switch chamber with contact cleaner then heating up the external solder terminals with a soldering iron. This causes the cleaner to bubble over the contacts as it evaporates.

I found this method works well and may save the job of dismantling the switch completely.

Liam

8th May 2018, 4:32 pm	#21
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,005	Re: Unusual problem? Mains switch... On old gear it's quite normal for the lubricant in on/off switches to dry out to the point where it totally gums-up the switch action: this applies both to the rotary built-into-volume-control kind of switches and on/off toggle-switches. A good blast with switch-cleaner (in the past servicemen would have used Carbon Tetrachloride but that's been banned for decades) and a few cycles of turning-on-and-off, followed by a squib of Electrolube will usually fix the problem.

10th May 2018, 4:57 pm	#23
Voxophone Hexode Join Date: Oct 2015 Location: Sunderland, Tyne and Wear, UK. Posts: 340	Re: Unusual problem? Mains switch... I've had this problem a few times recently. Someone on here suggested flooding the switch chamber with contact cleaner then heating up the external solder terminals with a soldering iron. This causes the cleaner to bubble over the contacts as it evaporates. I found this method works well and may save the job of dismantling the switch completely. Liam