Globe Queen... Power Tube Considerations

[KC4VWU]

Hi Everyone,
                   I've been on hiatus for a while. Just checking back in and trying to get things squared away for some serious QSO time this season.
                   At the moment, it's looking like I'll be using a GK 400 that I acquired at the Shelby 'fest this year. It's pretty much complete, and I believe there shouldn't be much trouble having it up and running on 75m in a couple of weeks; knock on wood, of course.
                  One quick question though, if I may. Are there any suggestions from the veterans on bringing up the V70D's and TZ-40 mod toobs properly? Other than just babying them slowly, any super fragile filaments or other notorious problems; don't want to cause no undue damage, i.e., my unfortunate BTA 500R moment of stupidity. I know I could do some swap-a-roo with the toobs, but I'd just rather do a quick clean up, check out, and run it as close to original as possible. No stress that way, and I could actually have some talk time instead of full resto headaches.  I have a GK 500 in progress (2 years and counting); just want to have a little fun on the air this year is all.

73, Phil

[N2DTS]

The 400 might be the best rig WRL ever made.
You can also run 8005 and 811a tubes I think.
WA3JVJ used to run a 400 (the wall of sound) with lots of mods and various modulators, and it was amazing the amount of modulation he could put on that RF deck.

Of course, you can upgrade the 400 a LOT, in just about every respect, like all WRL, everything is very marginal.

[WD5JKO]

Phil,

    Other than running the filaments only for a few hours, I don't think there is much you can do. Those tubes will probably be OK, but if not finding replacements will be a challenge since those tubes have 7.5V filaments.

Some possibilities at 7.5V are the 5514 (modulator), and 808 (both modulator and RF). The 808's pull 4 amps though. If you change filament transformers, then the options increase a lot. The 812 would be a good RF tube (6.3V @ 4 amps), and 811 for modulator (6.3V @ 4A). Also as Brett suggested, the 8005 would be a neat tube to use (10V @ 3.25A).

Jim
Wd5JKO

[W4AAB]

The 5514's in my GK 500 were replaced with 811-A's and the filament transformer was changed to 6.3 VAC.
                               Joe W4AAB

[KC4VWU]

Hi Guys,
            Thanks for the replies and suggestions. It may be a better option to switch the mod tubes to 811A's, since the TZ-40's are not as common and would probably be better suited to something more "showey"; maybe like an open frame desktop rack style ala Gross Radio's CB-25. However fast the wheels are turning, I'm rambling at this point, so back to the project at hand.
             After a brief visual inspection,and slow power up of the P/S and exciter chassis, I loaded it up to full rated power into a cantenna. Similar respectful treatment of the mod deck found good audio when inserted into the chain, but a little too much gain resulted in some audible arcing; didn't see where, but it subsided upon several other test transmissions. Until..... Well, it finally came to an abrupt end when under another short test tx., the supplies started to grunt under a fairly evident steady state short; so hopefully, no mod iron was harmed in these tests! I'll start backtracking tonight and try to get some pictures of the process as well.

...Phil       

[KC4VWU]

Here's a before look underneath the mod deck... still working to remove the unnecessary clutter.

[N2DTS]

A selinium rectifier!
Boy do they stink when you burn one up.

[KC4VWU]

Yeah! That's crazy isn't it? Probably been in there for decades; was the rectifier for the PTT relay power ckt. One of the "unnecessary" items that was yanked; I'll try to get an "after" pic a little later tonight. Still some loose ends to tie up. It's back up and running again, found this... not soldered, just pulled the leg right out. I believe I found the arcing noise