Does anyone know of the 6G8G valve has a history if falling to bits? I've got two, both from identical AWA Radiolas and both are suffering loose bases and equally loose wiring between the globe and the base pins.

I'm fairly sure I don't have any spares so before I begin dissecting one to repair it I just want to know if this particular valve is known to suffer this problem.

Though someone may have to correct me, I think the 6G8G is a uniquely Australian valve and was first developed by AWV as the 6B7S. I have four 6G8G's amongst my spares, all made by AWV. Two are branded AWV, one Mullard and the other Philips. Only the Philips and Mullard ones have loose bases. Loose bases are common with a lot of used valves from the octal and pre-octal era. Many years ago, Peter Lankshear wrote an article in EA about repairing valves with loose and broken bases.

Loose bases on octals & similar valves are common; One of the ways of assisting this in happening is to pull the valves out by the envelope.

Araldite (slow one) solves the problem, but it is not recommended to go full circle, on the base by some.

I normally apply a small amount then run insulation tape around the base to glass interface, to stop the adhesive running down the side.

You do not attempt to seperate the base from the envelope, if it is avoidable,as you may not ever get the wires back into their holes / right holes even by tacking a snake wire on.

A small amount of slow reacting Araldite can often soak into a pin base & hold it. an old valve socket can be used to maintain correct spacing, untill it reacts.

Do not push fully home & hang upside down in a valve shield or put upside down ina cup. We do not need to glue the tube to the socket.

On valves with a loose top cap, a smear of Araldite is good, if you can get it under the cap. Worst case scenario is you remove the cap. If the cap has come off and there is wire showing, that is fixable.

In all cases loose does not mean that the valve will not work.

Marc

Many years ago, Peter Lankshear wrote an article in EA about repairing valves with loose and broken bases.

Yeah, I cut my teeth on valve repair with that article. I even managed to use a warding file to grind away the exhaust tip to expose a snapped wire for a top cap once. All a long time ago. I am hoping I still 'have it'!

Loose bases on octals & similar valves are common

Rather too common sometimes. I think what provoked me to ask this question is that I have two identical valves from the same model radio which were worlds apart until I bought them and they both suffer the same problem. It looks like there's a dry joint or broken wire though - I can confirm that the socket is in good order.

Many years ago, Peter Lankshear wrote an article in EA about repairing valves with loose and broken bases.

"Repairing Valves" April 1990 issue.

"Rejuvenating Valves" January 1992 issue.

What kind of faults do these 6G8G's present?

Also, what about the batch number? If they are from the same model radio, maybe they are from the same batch. I have seen this before.

Nevertheless, both 6G8G's look like being potential patients for the valve hospital!

That said, I've always thought the 6B7S/6G8G's (same valve, dfferent base) wasn't a very reliable valve to begin with. Years of bulk testing used valves has shown a high rate of faults, like inter-element shorts and low emission, from these valves compared to other types. As a result, good examples are a lot harder to come by.

I haven't tested my four 6G8G's yet. I'll do that when I get home tonight.

Other AWV valve types with reliability issues that come to mind are 6AR7GT and 6BV7.

Since a lot a valve types will never be made again, we all have to do our best to preserve what stocks remain if we wish to continue with enjoying our hobby.

Cheers.

Both mine exhibit the same fault - intermittent operation, which suggests the dry joint/busted wire scenario. If I flick the valve with the back of my finger it'll come good for a bit then cark it again. No loose parts inside the globe but the bases on both valves are loose enough to cause problems.

I'm going to go out to the garage and sus out my collection of spare valves to see if I have any spares.

Now let us be pedantic. 6B7 is a 6B8 with a different base.

6G8 is a 6B7S which is not quite the same draws a little more current. They are pin interchangeable, but you may not get the same result.

Marc

Hi Marc.

I have to disagree.

Yes indeed, a 6B7 did become a 6B8.

The 6B7S, with some similarities to a 6B7, was an Australian designed valve. AWA had an affiliation with RCA and the 6B7S along with some Australian designed battery valves, were all given RMA type designations. When the octal valve era kicked in here during the late 1930's, the 6B7S simply became a 6G8G. According to the valve data I have, they are the same electrically.

In North America, you have a Canadian Rogers 6B7S. Anyone familiar with Rogers valves would know that they were fond of spray coating their valves with a grey metallic shield. The "S" on the end of a RMA type designation on Rogers valves indicate a grey spray coated metallic shield. The Rogers 6B7S is electrically a 6B7/6B8.

There are some great books dealing with valve history & genealogy: The Saga Of The Vacuum Tube, by Gerald F.J. Tyne & Tube Lore, by Ludwell Sibley.

Cheers.

Hi again, Marc.

I think I may have misunderstood your previous post. To me it read that there were differences between 6B7S & 6G8G. In the clear light of day I now see you were pointing out the differences between 6B7/6B8 & 6B7S/6G8G.

Just wanted to clear that up.

Cheers.

I needed a 6G8G and there is an American equivelant the 6B8G that I found.

Vic