[RGallahue]

A friend brought me a 1933 Ford car radio to see if it might be repairable.  Its the Grigsby Grunow chassis with the reverse dial.  It appears that an exploded cap caused the failure, but rather than repair it, the original owner knew where the gold was; the tubes! (2) 6E7, (1) 6A7-S, (1) 6C7 and (1) 6Y5, (all shielded) were removed.

I have explored the possible renovation with modern components (Aurora), but am trying to avoid the cost as I want him to remain a friend.  Thus, I have spend some time looking for tubes, and without much success.  (1) 6E7 out on ebay currently, but these tubes are obviously few and far between.  Looking for ideas as to sources for these tubes or if there is a serviceable Grigsby or Zenith chassis out there (again that is not $500+). 

I just thought that perhaps one of you folks might just have something sitting in your junk boxes out there.  BTW, I will be at the Charlotte AWS convention in March.

Any ideas or thoughts that you may have are greatly appreciated.

[GarySP]

Hello Richard. Bob Dobush at FindATube.com is my go-to for tubes. Good service and reasonably priced.
https://findatube.com/

Gary

[Arran]

Let's have a look in the 1937 Sylvania tube manual that I have. The 6E7 is a variable Mu, RF pentode, so that would be used for both the IF and the RF tubes. According to this book electrically it's the same as a 6D6, but it has a 7 pin base rather then a six pin one, pin 5 on the 6E6 is not used. The next tube, the 6A7S is just a 6A7 with a metal spray coating, a Goat shield is a viable go around unless you want to experiment with metallic paints on glass. The 6C7 is a dual diode, triode, so likely performing the first audio, detector, and AVC functions, again the buggers used a seven pin base as opposed to a six pin, nothing is connected to pin 3, but electrically I can't find an exact sub at this time, but a 6R7 or 6R7G looks to be the closest, which are octal based. As for the 6Y5 it looks like an 84 (or a 6X5) would be the closest electrically, actually an improvement since it can deliver more DC output current, and uses a 500 ma heater rather then an 800 ma heater, but the 84 uses a 5 pin base rather then a 6 pin one, but pin 2 on the 6Y5 is unused anyhow. In three cases you would either need to change the socket, or build an adapter (if there is room for one).
Unlike with Rogers in Canada, Grigsby Grunow went belly up in 1934, and the replacements stopped being made at least a decade earlier then the Rogers ones, so the tubes may have been pinched from the car radio a long time ago. Rogers also had the good sense to make mostly standard tubes with spray shields, and even boasted that you could sub them for the new RCA metal tubes when they came out, on their octal types they followed the number with the letter "M" for metal spray, as opposed to "G" for the standard glass octal types, or "S" on the older based spray shield tubes. Sometimes they would invent their own number like a "41M" but it was really just a 6K6G with a metal spray coating, which a power amplifier tube does not need. There were four weird ones they started making during the mid to late 1930s, one was the 2X3 (half of a 5Y3 in pinout), a 2Y3 which I have never seen (something akin to half a 5U4) a 6X6 which was magic eye, and a tube called a 6F7M (a 6F7 pentode triode with an octal base).
Regards
Arran

[Arran]

Apparently a substitute for the 6C7 is an 85, so that would look less out of place then a 6R7, but there are 6C7s out there, 6E7s are a little harder to find. For the 6Y5 I would just make an adapter for an #84 tube, six pin to five pin. 
Regards
Arran

[RGallahue]

Gary and Arran,

Thanks a lot for the help and the ideas.  May look at doing that 84 substitution.  Looks like the Findatube is indeed the place to go, had not realized that he was out there, quite a treasure trove of tubes. 

Still mining through this thing to make sure I don't hit any other roadblocks as the mud daubers had quite the nest going in there.  We shall see if we can get this thing resurrected.

I deeply appreciate the assistance!

[Arran]

Richard;
It's just something we have to do from time to time, especially when one plays with Rogers-Majestic built sets, or later G-G built sets in the U.S. Some of the vintage TV guys may have to do this with some horizontal output tubes in early colour sets, the cost of one of the ones Brand Z used are ridiculous now because there was some sort of transceiver that used the same tube, and they are known to fail, a NOS replacement can cost up to $60 or more!!!
Regards
Arran

[radiorich]

Richard,
Yes , I have had to sub that tube too in the past like Arran said the cost has gone through the roof all of my early tv's are B/W ones .

Sincerely Richard