[gary rabbitt]

Hi,
I am almost ready to power up the 38-3 on a Variac.
The only tube I am missing from my set is the 6H6G.
I have several 6H6 metal ones, but they will not fit into the box shield base. Even cutting down the tube base it wtill not fit.

I searched thru my tubes and didn't have a 6H6G, so what I want to know is if that tube would interchange directly, or is there something attached to the metal housing and cause a problem? I say no, but I want to make sure.

I don't like to modify a set too much, but if I expand the opening on the tube shield base, a shorty 6H6 would go in. The shield would hide the expansion, so that if I eventually got the correct glass tube, I"d still be able to use the shield.

Thanks guys,
Gary.

[Ron Ramirez]

Hi Gary

Electrically, a 6H6 and 6H6G are identical. Philco put those shield bases in their 1938 models to prevent the use of RCA (metal) tubes. Nice, huh? But you have to remember, Philco and RCA were at odds with one another throughout the 1930s.

If you have a junk 1937 Philco chassis, you could switch the 1938 shield base to a 1937 type - they are made differently, so that metal and later GT tubes will fit inside them. I've had to do that before. When the shield is in place, no-one will know the difference. It will require removing the old tube socket rivets and then re-riveting afterward. But, I would think, anyone who can totally rebuild a 1937/38 Philco off-on-tone switch could easily re-rivet a tube shield base to a chassis!

Good luck, however you decide to proceed.

[gary rabbitt]

Thanks Ron,

I had heard about the rivalry about the tubes before, so I thought this was the case here.
Although I could "probably" redo the riveting, I think I'll open up the original shield base to accept the smaller tube for now. That way all the shields will look the same.
Take care,
Gary.

[planigan]

gray rabbitt, I have to agree with Ron, anyone who has the skill and patience to rebuild that swirch can do anything. By the was, the 6H6 metal tube is its shield and goes to pin one which on your set
1: May not be grounded or
2: May have been used as a
connecting point and can't
be grounded.

Good luck. PL

[Texasrocker]

I have found that my handheld dremmel-tool comes in very handy (with small metal cutting disc attached) does a nice clean job *opening* up those old Philco tube shield bases to accept the RCA metal-type tubes also if needed! Orig shield still fits if your careful in the modification also. (to keep originality).The dremmel tool also works well for carefully removing old orig rivets on all tube sockets if broken (need replacement) , or to change out tube shield chassis mounts from model-to-model replaced with a couple new rivets. Harbor Freight also has a low-priced version of the dremmel tool w/ accessories kit that is much less expensive!! Even tho I dont need to use it often, it sure comes in handy when I need to address replacing broken tube sockets, etc, spkr trans mounted to spkr, etc. Sure beats drill-bits for those *touchy* jobs!!

[gary rabbitt]

Hi Randal,

My Dremel is a renamed one from Sears I bought many years ago. Same tool though, I have used it for a lot of things. I recently had my dentis save the used burrs he usuall throws away, and I bought the mandrel (not Barbara) to hold those little things. They sure come in handy for those tiny surgery jobs Even to trim a veneer repair along scrollwork they seem to cut very well.

I used an ugly but high test 6H6 and shaved some of the bakelite off of the tube base, Just the small lip around the edge. Then opened the shield opening just enough to take the tube. Didn't take much and the original shield mount is in place.
Looks funny, but it works until I come across a glass 6H6.

Planagan, I checked the pin 1 and the terminal/connection is not even in the tube socket, so that was not a problem.
Thanks again guys,


Hello down there!
[Image: http://aycu11.webshots.com/image/48610/2...538_fs.jpg]

[Image: http://aycu12.webshots.com/image/46491/2...437_fs.jpg]

[Texasrocker]

Great job on the modification indeed!! Thanks for posting the pics also!! Since the small metal 6H6 tubes are still in great supply,(lower cost also) and those special-base 6H6 G tubes are rare and cost much more to boot,you just did yourself (and next owner if ever?)... a great favor by removing that excess metal on the tube-shield base!! I also appreciate "originality" and all, but lets face it. Your modification just saved another Philco to be enjoyed many,many yrs in the future with a more modern type metal 6H6 tube (JAN type metal tubes are still in great supply!)....or can be used with the orig tube if desired. You can bet the next tech that restores that chassis after were all long-gone, will also appreciate the work you have done when the tube needs replaced many yrs in the future!! Thats what I call "non-invasive" cosmetic-surgery!!! Great Job!!! Randal

[planigan]

grayrabbit, that looks great. After looking at the photographs I have a suggestion for the next time you run into this problem. With that type of shield "bracket" would it be possible to cut the shield bracket down one side, pry it open a bit to get tube in and let it snap back after. When you replace the shield itself it would pull it together and cover the cut. I don't know if the base of the tube would fit after its in socket and below the circular opening in the top that was too small a diameter to let it pass. That is, when the tube is insert is the base below that opening? PL

[etech]

Hi Gary,

Nice job on the shield modification for the 6H6. Fortunately, my 37-116 uses the square shields also, but they are big enough to accept the metal tubes.

However, Planigan's post made me think of another idea. In the past, I have made an adaptor to use a 1619 tube in place of a 45 tube by using an old 45 tube base and an octal socket installed in it. Maybe you could do the same thing. Just use an old octal glass tube base and install a new octal socket on top of that base. The adaptor would allow enough clearance to get past the shield mount? Oh well, you know what they say about idle minds, lol!

Ed

[gary rabbitt]

Hi Guys,
Thanks for comments.
Ed, I thought about changing the socket and all but decided against it. I wanted to make the mod as simple as possible, and retaint the original square shield.

I see the idea behind the "cut" tube shield base, but enlarging the hole would be much simpler, while retaining the solid original base.

If someone were to replace my "cut down" metal tube, they may have to widen the shield mount a little more. All I ground off the base was the tiny lip which was less then 1/32" maybe. Perhaps I should go ahead and do that (enlarge the metal base) gauging it with an unground tube base.

One of these years I might run across a glass 6H6, I'm not worried about it though.
Take care guys, and thanks!
Gary.