[Gabe001]

Originally Posted by Sideband

This is becoming more common with the age of the sets. Most radios are stored (or have been stored) in less than ideal conditions and dampness plays a major role. Once the valve holder starts to 'track' (leakage between two pins usually where there is the greatest voltage difference) then it gradually gets worse and the tracking causes heat in a localised spot which gradually builds up causing the Paxolin to carbonise until it reaches a point where the leakage affects the operation of the valve.....

The only answer in that case is a new valve holder. Note that it's not only Paxolin valve holders that can track......

I had 10 minutes before work and I think I sorted it, more out of luck than anything else. On close inspection from a different angle here was a small charred area on the paxolin of the waveband switch at the edge of the metal strip linking s11 when the waveband switch is turned. This carries HT to anode (180v). It was only 2mm in diameter and would have been inconsequential if it weren't the place where the anchoring pin for the metal strip linking S2 S3 and S4 on the other side of the same switch emerges. I'll post a picture later. I have scooped out the charred area and I still need to triple check but it seems the short is gone.

There is still some work to be done. The radio isn't working so I may have either disturbed something or the abnormal voltage on V2 may have damaged it (which is what I think Lawrence is alluding to). I'll have a second look when I can but I don't think it'll take too long to sort out now.

Any advice on how I can stop this issue from recurring? Scraping out charred paxolin from a rather inaccessible area isn't an exact science, and I cannot realistically change the waveband switch. I'm tempted to disconnect the s11 wires from the waveband switch and leave them permanently connected, but I'm not sure whether this will affect the FM end of things. What do you think?

Thanks for the help

Gabriel