5U4 Shoulders or not

[kramden66]

I was wondering if you were restoring a TV that will be run a lot would you stick with 5U4 tubes that have shoulders or the later ones without shoulders ?

whats the difference besides age and size ?

thanks
Mike

[Zenith26kc20]

I use the 5U4GB types for anything that is going to run a lot. They have the latest improvements for that era.
For applications that let you see the tube the ST is great but I find they don't last as long.

[N2IXK]

The 5U4GB has a higher output current rating (300 mA vs 250 mA for the original 5U4G). The straight-sided bulb allows both ends of the internal structure to be supported, improving vibration/shock tolerance.

The original 5U4G tubes in the ST envelope are getting harder to find and more expensive, because some of the audiophool crowd is convinced that they "sound better".

[wa2ise]

Originally Posted by N2IXK

The original 5U4G tubes in the ST envelope are getting harder to find and more expensive, because some of the audiophool crowd is convinced that they "sound better".

Well they look cool. As for sounding better, I have a hard time believing what mechanism is involved that could make a difference there. The output tubes and driver and buffer tubes I can understand why (tubes tend to produce some amounts of 2nd harmonic, when down around 45dB it sounds pleasant to the ear).

[cbenham]

Originally Posted by Zenith26kc20

For applications that let you see the tube the ST is great but I find they don't last as long.

Hmm. Don't tell that to the two ST 5U4s in my RCA 630TS with 252 date codes.
It runs almost daily.

[marty59]

The newer 5U4GB's are a little more stout in design over the G's. However if your set was designed to use the G types then there should be no issue with either.

As for myself, I would use what I would have most of in my stock considering that the GB's are more plentiful to buy. You should get just as good of a service life out of either as well.

The 5U4 family of tubes were so commonly used and a popular choice that they are still abundant today. (however prices seem to be going up!)

[bob91343]

There is no question but that the ST tubes sound better. Just ding one on the side and listen closely. Yum!

[Electronic M]

Originally Posted by bob91343

There is no question but that the ST tubes sound better. Just ding one on the side and listen closely. Yum!

I dare you to post that on audio karma next time there is a debate on which rectifier tubes sound better. The responses to that should be priceless.

Jim's idea is a good approach (especially if on a budget or your xformer overheats with a normal 5U4), but if you make your own don't forget to add snubber caps across the diodes to reduce switching noise especially in radio applications.

[WISCOJIM]

Originally Posted by kramden66

I was wondering if you were restoring a TV that will be run a lot would you stick with 5U4 tubes that have shoulders or the later ones without shoulders ?

If a set is really going to run a lot of hours, I'd use a solid-state 5U4 to keep the heat and energy consumption down a bit.

[bob91343]

Also the color of the knobs is more important than most people realize.

I once knew an electric bass guitar player who insisted that the flecks in the paint on the solid wood body gave it a special tone. I should have tried to sell her this bridge I own.

And to stay on topic, yes the solid state replacements are definitely advisable, even if all you consider is the 15 W per 5U4 just for the filament. If you want it to be original, keep the tube handy to plug in when showing off the set. Then of course you can use the ST type for more dramatic effect.

[Username1]

Seems like for audio it would be better to have the one that can handle more current, and is more solidly built..... Then there is the argument that a rectifier tube doesn't actually do any sound amplification....... Anyway as for my 3 cents on audio while posting in the tv section.... I'd like to say nothing sounds like it should sound better than some of Carver's advertising pamphlets..... "Asymmetrically charge coupled, hyper-dine series receiver with sonic holography" They just sounded so cool and advanced even before you turned them on....... ahhhhhhh... oh, yah... I don't think they had 5U4's in em...

[Electronic M]

Originally Posted by Username1

... Then there is the argument that a rectifier tube doesn't actually do any sound amplification...

Good argument. It makes sense that the rectifier tube version wouldn't make a difference in performance or sound unless defective or if the PS was being operated near design limits. If b+ voltage variances occur with different rectifier tubes causing an effect on biasing of signal amplifying tubes I could see that causing an a distinct difference in perceived sound of rectifiers among those unaware of biasing.

I get SS vs. tube rectification having an effect on sound though due to switching noise and reverse leakage found only in solid state diodes....Which makes me wonder how bad selenium rectifiers are compared to tubes and silicon diodes....

[Username1]

Well all things working correctly and within limits, I'm just saying I would imagine you can't tell one good 5U4 from another, as long as it's all operating within limits.

[kx250rider]

I still feel like there's a "limitless" supply of 5U4s of all types, and honestly I've found that the GBs are more likely to short than the G or GA types. It's only my own opinion though, and I'm sure many will disagree. I know that since they haven't made 5U4Gs for half a century or more, they must be diminishing. But still at every swap meet or garage sale where there is a box of tubes, there is most always a 5U4G or two.

As far as "high usage" restored TVs, I'd still go with the correct style, or why restore a TV in the first place. If you put a wrong-style 5U4 in it, that's along the same theory as putting a new aftermarket digital fuel injection system on a 1938 Cadillac; sure it will run better and get great MPGs, and you can get new sensors and parts for it, but for what purpose???

Charles

[N2IXK]

Originally Posted by kx250rider

I know that since they haven't made 5U4Gs for half a century or more, they must be diminishing.

Actually, they are still being made:

http://www.amazon.com/Sovtek-5U4G-Du.../dp/B0002M71S0

http://www.sweetwater.com/store/detail/MB5U4G

http://www.tubeman.com/item196.htm

Apparently, the audio fetishist market is large enough to justify producing these, even if they are inferior to the straight bulb types. Makes perfect sense, considering that you can also buy 6SN7s with Western Electric style "tennis ball" bulbs on them:

http://www.jacmusic.com/chinatubes/6SN7-Globe-400.JPG

So they take a crappy Chinese 6SN7, and make it even MORE microphonic by removing the structural support and damping provided by the mica supports against the inside of the bulb. And then charge a premium for them!

If you want the best of all worlds, remove the 5U4G bulb from the base, install a pair of 1N4007s inside the base, then epoxy the bulb back on. Solid state reliability, reduced heat load, and the correct vintage look.