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A year or two ago, someone was inquiring if there was such a thing as a 6X5 with a 12V filament. 12X5 does not exist, but the 7 pin miniature 6X4 and12X4 doe as we all know.

I suppose one could pull the old " metal 6V6" trick, which used a 6AQ5 and an octal to 7 pin base adapter, all hidden under the ostensibly "6V6" metal shell. If you had one of these, the 6AQ5 could be removed, and a 12X4 inserted in its place, and a "metal 12X5" would be the result. The pinout might be all screwed up, depends if the internal wiring could be changed or not, or if it is even compatible at all... Yellow_Light_Colorz_PDT_11

There are probable Loctal 12/14V filament rectifiers, I don't have my books and manuals present for quick reference.


Well, it turns out that Bendix had some 6X5 variants:

5852 has a 6.3 V filament,

5838 has a 12.6 V filament, and

5839 has a 26.5 V filament.

Most of these are very difficult to find, one would probably have better luck finding NOS/NIB WE300Bs for $5 each... :o Yellow_Light_Colorz_PDT_04 Yellow_Light_Colorz_PDT_02 Yellow_Light_Colorz_PDT_03 Yellow_Light_Colorz_PDT_05

Can you say "unobtainium"

These are the kind of tube that are likely show up at hamfests and swapmeets for cheap, because the seller doesn't know what the heck they are Yellow_Light_Colorz_PDT_09

/ed B

I once considered building one of these:



But thought better of it, and donated my stock of 6X5 to a better cause. If you decide to make one, let me know how it works out. It's not exactly a 12 volt 6X5, but it does allow you to run a pair of 6X5 off a 12 volt supply...

I'm not sure what was behind the original question when it was raised ~2 years ago. But, here is a thought:

Some old radios, notably Zenith, used two 6X5s in full-wave rectification. Each tube's plates were in parallel. This provided additional B+ current beyond what could be supplied with a single (slightly puny) 6X5.

I see no reason why the two filaments couldn't be put in series for 12V.

IIRC, someone wanted to replace a 12X4 with an octal rectifier in a PAS-clone.

No problem with stringing the filaments in series, as the DC voltage is taken off the cathode(s),so there should not be any hum/ripple issues.

6AX5s could also be similarly connected if one needs a bit more current capability,

/ed B

FWIW, in the loctal tubes, 7X4 is near-equivalent to 6X5, and 7Z4 is heftier, more like a 6AX5 or perhaps 5Y3GT. THese have 6.3V filaments but they are also OK with 7V.

I've been digging thru the depths of the tube stash and found some NOS loctals, and sockets, so perhaps I'll work up an all-loctal SE or PP amp.

7F7 = 8SL7
7N7 - 6SN7
7A4 = 6J5
7B4 = 1/2 12AX7 Hi Mu Triode, mu = 100, Rp and gm slightly different
7C5 = 6V6GT
7X4 = 6X5
7Z4 = 6AX5 / 5Y3GT
7A6
7X6

and some others yet to be uncovered...

Most other loctals are various and sundry pentodes, diode-triode combinations, pentagrid converters, etc. All axcept teh rectifiers are readily available in "14V" filament versions as well (actually 12.6V, but still OK with 14V, as these were designed to be compatible with automobile storage battery voltages.

/ed B

Alas, I gave away most of my locktals as sockets until recently were unobtanium.

Cheers!

In the last couple of years, locktal sockets have become very much available. I got some teflon ones from Ned a couple years ago, and have some chinese / Russian ceramic ones on the way right now.

I also just snagged 8 NOS 7C5s for fairly cheap, and I have enough (hopefully still good) 7F7s, 7N7s and 7Z4s to assemble an all-loctal "6V6 equivalent" amp.

I wonder just who made or used any 9-pin "loctals", in my stash of weird tubes, I have one unmarked, unknown, mysterious 9 pin "loctal".

The only marking is "396" inked on the plate, inside the glass. The plate is of a strange triangular shape, as viewed from the top.

/ed B

The 9-pin loktals are European - I have some red metal ones (forgot the number). I made a chart of equivalents and near-equivalents: http://www.audiophool.cjb.net/Equiv_similar.htm

EWBrown wrote:FWIW, in the loctal tubes, 7X4 is near-equivalent to 6X5, and 7Z4 is heftier, more like a 6AX5 or perhaps 5Y3GT. THese have 6.3V filaments but they are also OK with 7V.

I've been digging thru the depths of the tube stash and found some NOS loctals, and sockets, so perhaps I'll work up an all-loctal SE or PP amp.

7F7 = 8SL7
7N7 - 6SN7
7A4 = 6J5
7B4 = 1/2 12AX7 Hi Mu Triode, mu = 100, Rp and gm slightly different
7C5 = 6V6GT
7X4 = 6X5
7Z4 = 6AX5 / 5Y3GT
7A6
7X6

and some others yet to be uncovered...

Most other loctals are various and sundry pentodes, diode-triode combinations, pentagrid converters, etc. All axcept teh rectifiers are readily available in "14V" filament versions as well (actually 12.6V, but still OK with 14V, as these were designed to be compatible with automobile storage battery voltages.

/ed B

I need the EWBrown Bible of compactrons to XXXX, and Loctals to XXXX.

Loctals bring back memories of the first radios I fixed

Cheers!

That 7Z4 is almost a 6CA4/EZ81 ...