Vidor CN420. Where do i start? - UK Vintage Radio Repair and Restoration Discussion Forum

MALC SCOTT · 2nd Oct 2009, 5:06 pm

Hi, i picked this up today for £1. It is complete with its batteries which seem to have corroded the chassis with the fumes from them over past 40 years.
Any ideas how to clean the corrosion from the chassis, or is it not worth bothering with?

Cheers, Malc

Ed_Dinning · 2nd Oct 2009, 5:21 pm

Hi Malc, they usually work well and are simple to repair.
A chain of PP3's is ideal for the HT. Usual caps to replace and some high value resistors in the AVC circuit that go even higher.
Should be a simple job.

Ed

julie_m · 2nd Oct 2009, 5:28 pm

Battery valve sets have a much easier time of it than their tethered-to-the-wall sisters, as the running cost per hour tends to ensure they spend most of their time switched off.

Hoik the valves out, change the capacitor connected to G1 of the DL just on general principle, prove continuity from HT+ to DL anode meaning LS txr is OK, reinsert valves and apply juice. (If you've nothing better, use a D cell for the LT and a stack of PP3s for the HT.)

If anything happens at all -- a crackle from the speaker, or even just the oscillator going -- it's worth bothering with.

Steve_P · 2nd Oct 2009, 5:33 pm

Well, remove but don't bin the batteries. They can be used to hide the PP3's and the 1.5v cell. (Or cells.)

Use sandpaper of varying degrees to get rid of the corrosion. Then it's the usual capacitor changes. Note that these battery valves don't physically light up. Be ready for that. They also tend to die.

Good sets when they work. Note : There is also a CN420A. The valves are not interchangable.

Cheers,

Steve P.

2nd Oct 2009, 5:06 pm	#1
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Vidor CN420. Where do i start? Hi, i picked this up today for £1. It is complete with its batteries which seem to have corroded the chassis with the fumes from them over past 40 years. Any ideas how to clean the corrosion from the chassis, or is it not worth bothering with? Cheers, Malc Attached Thumbnails __________________ Malc Scott

2nd Oct 2009, 5:21 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Vidor CN420. Where do i start? Hi Malc, they usually work well and are simple to repair. A chain of PP3's is ideal for the HT. Usual caps to replace and some high value resistors in the AVC circuit that go even higher. Should be a simple job. Ed

2nd Oct 2009, 5:28 pm	#3
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Vidor CN420. Where do i start? Battery valve sets have a much easier time of it than their tethered-to-the-wall sisters, as the running cost per hour tends to ensure they spend most of their time switched off. Hoik the valves out, change the capacitor connected to G1 of the DL just on general principle, prove continuity from HT+ to DL anode meaning LS txr is OK, reinsert valves and apply juice. (If you've nothing better, use a D cell for the LT and a stack of PP3s for the HT.) If anything happens at all -- a crackle from the speaker, or even just the oscillator going -- it's worth bothering with. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

2nd Oct 2009, 5:33 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Vidor CN420. Where do i start? Well, remove but don't bin the batteries. They can be used to hide the PP3's and the 1.5v cell. (Or cells.) Use sandpaper of varying degrees to get rid of the corrosion. Then it's the usual capacitor changes. Note that these battery valves don't physically light up. Be ready for that. They also tend to die. Good sets when they work. Note : There is also a CN420A. The valves are not interchangable. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?