6X4/EZ90 in a 6X5/EZ35 Octal bottle

Discussion in 'Glowing Bottle Tube Amp Forum' started by Squawker, Aug 10, 2020.

  1. Squawker

    Squawker Tele-Meister

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    Thinking about building a Champ 5C1/Silvertone 1301 kind of amp. I have a PT but I don't think it has 5V, so I was keen on a 6.3V octal recto - octal for the visuals, to match the 6SJ7 and 6V6.

    I have a couple of Brimar 6X5GT/EZ35. Word is, the early 6X5s are an accident waiting to fry your PT, and that the later Brimar type with the offset anodes is much better. But these ones don't resemble either - they look more like a 6X4/EZ90 in a big octal bottle.

    Which is probably a good thing - just struct me as a bit odd. The code is 3F2/432 which is 3 week of June 19x2, type 6X5GT - three digit type code implies 1952. In 1962 it should've been 1432 - they're priced at 12s 6d som they must be pre-'71.

    Anyway - has anyone seen 6X5s like this before? Can anyone confirm that they're 6X4s (EZ90s) in a big bottle.


    IMG_20200810_213413.jpg IMG_20200810_213430.jpg
     
  2. Wally

    Wally Telefied Ad Free Member

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    Squawker, what voltage does that HT secondary winding provide? I ask because you might take a look at the 6AX5 rectifier. It drops 70 volts, so unless your PT has enough HT voltage, this tube might not be what you want since the 6X4 and this 6X5 you are cnsider8ng both drop 22 volts, correct? As for the other parameters, you would have to do your due diligence.
     
  3. Squawker

    Squawker Tele-Meister

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    Now that's the thing - the one I was thinking of cannibalizing is 260-0-260 which is a bit on the low side, considering the Champ-a-likes tend to be around 320-0-320, so I'd want to drop as little as possible both in the rectifier and in the smoothing stages. As such, the 6X5 looks promising. The alternative will be to source a proper Champ PT and use a 5Y3 like the original.

    But turns out it has a 5V winding, so maybe 5AR4/GZ34 is the smart choice for an efficient rectifier.

    Or I could take my own excellent advice on small single-ended amps and go SS!

    Too many choices - but I have the 6X5GTs and I might as well use them. Visual inspection, side by side, with a Brimar EZ90/6X4 suggests they truly are identical inside the bottle, which is a good thing(tm), given the original 6X5's reputation for unreliability.
     
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