[Jayce]

I finally decided to give my recently purchased and of course restored Zenith 7S633 a little use tonight and I am rather impressed with this radio. Like some sites say, you definitely need a long wire for shortwave, but this radio does quite well on AM, even in the house with all the modern electrical noise. In fact, this radio rejects the noise better than most of my other old radios, whether they use an internal or line antenna. Sound is almost FM quality on our local AM station and it can at least receive other stations I can't usually get. Strength depends on how the radio is positioned of course as internal antennas are always at least a little directional. Now my big issue is that it has a 6X5GT in there that looks like new. I am not very handy, so building a solid-state replacement is out of the question for me, so I am wondering where I can find one for this radio and one other Zenith I plan to keep that uses this tube? I really don't want to chance a fried transformer from a suddenly shorted 6X5!

[NostalgiaRadioTime]

You could try a 6AX5-GT in place of the 6X5. These are far less prone to shorting out as I've been told.

[LarryFS]

I use a 6X5WGT based on a recommendation from a person on another forum.  I've also seen a recommendation for a solid state version of the 6X5 sold at https://tedweber.com/wx5/. 

Larry

[Jayce]

I checked on the 6AX5GT and you are right about that. Even my tube substitution manuals list it as a sub, but caution that the tube uses parallel filament circuits. Further research also ended that option as that tube draws over twice the current of the 6X5. I guess that is ok with larger transformers, but not Zeniths. Wish it would work as I have a used example (untested) and a brand new in the box 6AX5 from RCA.
I too have heard about the 6X5WGT, but don't currently have any in my personal stock. I have a used 6X5GT and an apparently new RCA 6X5GT. The one currently in the radio is a 6X5GT and I think a Sylvania. I am pondering that WX5 solid state swap as well, but would still try to find a 'safer' 6X5 while researching that. Might have to see what my friend has for new tubes left at his shop and see if I can at least get a 6X5WGT or two.

[murf]

I would also add a fuse for extra protection.
I have used the solid state replacements and heard that they can cause problems as you have instant power instead of the slow warmup of the tube.
Can put undue strain on other tubes.
murf

[Jayce]

I went to my buddy's shop today and although I didn't score a 6X5WGT, I did find a couple possible replacements. One is a very stubby GE tube with the 'X' shaped plates that looks like a late production tube and the other is what appears to be a NOS Sylvania which also has 'X' like plates. (Think one of those old, cast-iron Railroad cross-bucks) Both checked excellent on his Jackson tube tester, so I brought them home to try out. The 6X5GT currently in the radio is one of those with the plates sandwiched together so tight you can't tell there are two plates. He also had a little 1939 GE ready to go for me, so win-win there. I tried to get a picture of the tubes, but I think a new camera is in order soon! Here is what I got: