Since there has been some talk about the 6X5GT valve I thought this thread may be an interesting read.

Even though I am aware of dire warnings about the 6X5 shorting cathode to heater, I've never had any issues with 6X5GTs myself other than them dying of old age. It always struck me as odd that the 6X5 was used in the valve-unfriendly environment of car radios without trouble.

So that's a very interesting read, especially about the shouldered or "G" version and the transformers in certain Zenith radios.

I can't say I remember seeing a 6X5G. Were they ever made here in the G form factor? I have a hunch that the 5Y3G was dominating the scene at the time even though it required its own heater winding on the power transformer. I'm in much the same boat with the 6X5GT, got a few radios with them and they have been reliable.

There's an interesting link in your link Brad about cutting the glass tube of defective 5Y3's to fit diodes and a small globe inside the glass tube. Some people will go to a lot of trouble but I think if I ever have to opt for a solid state rectifier I'd just put the diodes and resistor under the socket. Cutting the tube with a red hot wire sounds like fun though and I can't wait to try that out!

Yes, it's even more extreme than fitting new condensers inside the packaging of old ones to keep the look. I'm not one for solid state conversions - a fuel injected V6 engine isn't at home under the bonnet of an FX Holden though either way, I wouldn't worry about doing any of this unless the chassis was to be a display piece at an exhibition.

I wonder if a factor in this 6X5G problem is related to the 110volt supply current for transformers in American radios. Presumably the flux has to work harder than our ~240volt transformers and may put more strain on the B+ source coil if it is leaky?

Anyway I have two radios running happily on 6X5GTs - a few old spares and several new Russian copies. I gather the GT does not have the same reputation issue in North America.

Maven

I am not sure these days. When I did my pre-apprenticeship course something like 25 or 26 years ago I learned all about flux density and even how to design transformers correctly but with the passage of time and not doing that for a living most of that information is lost to me.

Assuming the secondary windings in the transformer in a given AU and US radio are the same I would imagine the basic requirements are that the wire gauge on the primary winding in the US transformer would need to be twice the size of that in the AU transformer, knowing that if the voltage halves then the current flow will double to achieve the same result at the secondary windings. Because the mains frequency over there is 60Hz the core of the transformer could be slightly smaller than that on the AU transformer. There's probably other things to consider though I just don't remember to be honest. I was always much better with practice than theory.

I'll tell you something I did have in a radio once and I don't remember the valve type - a case where the filament in a valve was popping out the top of its sleeve and curling over like the top end of a walking stick. I never rejected the valve because it still worked. Why that happened to the filament is a bit of a mystery. It could just be a matter of poor positioning by the assembler - it would have been boring work holding a pair of tweezers and sticking all that together all day, every day. Or perhaps a filament designed for a larger valve got in the mix and ended up in a sleeve for a shorter valve.

- a case where the filament in a valve was popping out the top of its sleeve and curling over like the top end of a walking stick.

Both 6X4 and 6X5GT can do this. I have seen this often and the valve seems to still work fine in most cases.

As to whether 6X5G's were manufactured in Australia, I know AWV never made them. I'm not sure about Philips/Miniwatt, but I have this feeling (I could be wrong) they may have made them here briefly in a ST14 package. The common imported 6X5G's were in a ST12 package.

Prior to WW2 the only locally made radios that used 6X5's were vibrator sets and these were mainly car radios. Most of these vibrator sets used the original metal 6X5's. The post war period when radio manufacturing resumed is when the 6X5's became more common as a rectifier in domestic radios here. By this time the 6X5GT had been fully developed and this is why we don't see too many of the 6X5G.

As for close relatives of the 6X5, similar valves are the early 1930's pre-octal 6Z4/84, the European P-base or side contact EZ2 and the Sylvania Loktal 7Y4.

As said in that Canadian link and you will find more on Antique radio forum. Zenith was marginal & any over stress tended to wipe out the transformers. This not helped by the change of mains voltage and the lack of primary tappings on many US radio's to compensate: Many of ours had three.

The 6X5 was originally designed for car radio, but somehow when making it rugged, they lost the plot. There was an under & over plate design which was one that had a terrible habit of warping & shorting. There is a litany of disasters on the US forum, regarding damage caused by them going feral.

Later designs seem to have improved them.

Marc

Here's a dramatised video showing the manufacture of Western Electric shouldered type valves:

https://www.youtube.com/watch?v=_-JzxX75oYc.

Interesting to reflect that the periodic table ended at 92 (Uranium) back then.

To quote GTC:-

So that's a very interesting read, especially about the shouldered or "G" version and the transformers in certain Zenith radios.

Again not the voice of experience..

Mostly thats the info I found and why I think that the GT versions may have possibly inherited a lot of bad press (thought some as I said my have borough there own probs to the table).

You guys would know better then I but I think the 5y3 (80) was probably the more popular on the radio scene then G version of 6X5 here (if it was produced here?) and its only later that the GT version appeared and were used here (cost cutting probably) ...also as has been pointed out our Transformers were better built and most of our radios were 4 valve jobbies.

seems mounting can be trap with the 5y3...not something your hear mention of often.

Edit

further

I should add, I dont know if its a "clocks ticking" Scenario with regard to the HK leakage...as in its inevitable that this break down will happen over time...

But we dont seem to have the problems the US did
which is a good thing cause they seem to be a well used rectifier here