Valve sockets

[richwalters]

Anyone come across good quality IO valve bases to recommend. ??......Not those white ceramic ones from the Far East which after replacement caused the problem. There must be some good hi-end makes about.

I've reconditioned a high power pentode amp and at a particular level I get flash-over from pin3 (anode) to case at 600V B+.

Perhaps I am forced to clean up the original McMurdo phenol types. Note after July this year they won't RoHS compliant.. so buy'em up.


richj

[anatech]

Hi Rich,
I think that's a plan. You could try some HV dope in that area. Is the saddle too close to the pin? You may be able to bend it out a little.

-Chris

[richwalters]

thanks Chris...There's a bit more to this...vendor mentioned that sometime in the past the amp had a rough life......the usual symptoms of corroded tag strips, dog end/ fag stains..., beer spilt on it frothed down on the tubes and fungused on the top plate. It was common trait in the early days for beer mugs to be put on top of amp cages. I did it, so did everyone else and sure enough with time and vibration it would spill over. Under the magif glass the original Mc Murdo phenol socket has a thin arc track on it but strangey not right across to the inner conductor....so I shall attempt to refit and scrape the burnt and HV dope it or failing that some conform lacquer. McMurdo produced the best sockets at that time.
Looking at this closer, on all tubes the pins underneath are somewhat press expanded near the tube base so when the tube is pushed well home in the socket it's that little expanded part that comes just that little bit closer electrically to the chassis. It's worth looking under an IO tube and you'll see what I mean. The solution is obvious, a bit of hard phenol paper with place for spigot and 8 holes just to provide enough offset height.

There must be loads of users shoving more than 600V through IO sockets and getting away without problems....I thought that the practical limit was lower.

richj

[anatech]

Hi Rich,
Years of repairing amplifiers in similar condition. 600 V is high. Under power it's even higher. I have carved out tracks and filled them with dope before.

Good luck!,

-Chris

[Geek]

Originally posted by richwalters
Not those white ceramic ones from the Far East which after replacement caused the problem.

There is a type that's designed for HV. One piece unit and the pins are recessed to avoid arc-over.

[eeka chu]

Audio Note UK make and sell, through distributors only now, a line of valve bases. They're silver plated etc, all that'd you'd expect from Audio Note; price included.

Although, before posting this I did have to check that they actually made an Octal form given their hatred of anything that has more than four terminals on it.

[richwalters]

I might get scolded for this but by far the best H.V design tube socket is used on the 807 base, i.e UX4. In future for MI apps I shall fix IO valve sockets on some scrap single sided ex pcb with copper removed. Cheapest solutions.

thanks for all replies

richj

[Makofoed-6sn7]

Hello,

In a amplifier I made for a guitar player he wanted a clean amp and to help that a little bit I used about 500-600v on the anode, I dont remember exactley. The problem that occured to me was a constant arc on the underside of the socket on pin 3 that put the cloth wire on fire! A lot of smoke. My solution was first, replace the wires and then use heatshrink tubeing on the pin so NO metal was too be seen. That fixed the problem, no problem on the top of the socket, they are high quality so that the pins are pretty deep in the socket, don't remeber were I got them. Also, In a Marshall amp I fixed for a friend there was a bad socket, but he coulden't afford a new one, my solution there was a litte ring of heatshrink tube on pin 3 on one of the output tubes that sat in the bad socket, it was just enough to keep it from arcing.

Beer spill? That is noting...
I got amp full of pig blood for repair once!! Some of those black metal bands arn't quite good... It was not fun to clean that amp, when you get hot water on pig blood it smells! Not to mention the hot output tubes with blood...

Best regards,
Magnus Kofoed

[Giaime]

Originally posted by Makofoed-6sn7
I got amp full of pig blood for repair once!! Some of those black metal bands arn't quite good... It was not fun to clean that amp, when you get hot water on pig blood it smells! Not to mention the hot output tubes with blood...

That's a very death metal story! My best compliments (for you to have repaired such an amp, and for the band... )