Anyone used these before?

dougsta

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These are the Loctal base version of the old WW2 vintage 807 valve which I believe is the RF transmitter version of the 6L6.
The codes printed on the valve are5B/254M and CV428 (Military designation)

IMG_8434.jpg

I have a bunch of Loctal sockets and anode top caps in the parts drawer, I got these for £5 each.

The data sheet shows it can take 600v dc on the anode because it's taken out through a top cap, with up to 80W in a push pull pair.

CV428.jpg

stc 5B 254.jpg

Interesting...

Doug
 
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NTC

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I would look to make a hifi amplifier out of those. Or a Bass amp. Do you need an 80 watt guitar amp?
 

dougsta

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I would look to make a hifi amplifier out of those. Or a Bass amp. Do you need an 80 watt guitar amp?

I was thinking they might work well in my 'Summer project' thread.

I'm converting a solid state Fender Frontman 212R combo into a tube amp.
 

MickM

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Fascinating! Had to google "Loctal". A lot of ... "strong opinions" out there on them. Not a lot of love shown!

Any idea why they don't recommend cathode biasing?
The top connection is interesting. Looks like spark plugs!

View attachment 846451


If I was out and saw somebody plugged into a chicken wire covered rig similar to that, I would have to make a point of talking to them when they took a break. The look of the tubes alone would make me do it.
 

dougsta

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I've got a local version of a 6V6, the '7C5' and the valve in my avatar is signal pentode, a 7B7, also got some 7C6 and 7Y4.

The top caps look like something from a '50s horror B movie.

They recommend silicone rubber coated wire to connect the top cap.
 

printer2

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Fascinating! Had to google "Loctal". A lot of ... "strong opinions" out there on them. Not a lot of love shown!

Any idea why they don't recommend cathode biasing?
The top connection is interesting. Looks like spark plugs!

View attachment 846451
Don't forget, they were meant for RF duty not audio. Might have something to do with it.
 

dougsta

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Here's what the wiki article says on the 807:

"The electrically similar 6L6 was not favored by hams because high transient voltages on the anode when operating in class C could cause a flashover between pins 2 and 3 on the octal base, whereas the 807 had the anode connected to a top cap, physically distant from all the base pins."

I try a test in an 6L6GC based output section rewired for the Loctal base and top anode.
 

Musekatcher

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You guys are always coming up with more obscure interesting stuff, I'm guessing loctal is a jam of "lock" and "octal"? Looks like they added a locking feature on the center guide, to maintain connection during vibration and motion.
 

dougsta

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You guys are always coming up with more obscure interesting stuff, I'm guessing loctal is a jam of "lock" and "octal"? Looks like they added a locking feature on the center guide, to maintain connection during vibration and motion.

Exactly, especially for use in autos, don't want those glass tubes falling out.
The base, on the ones I have, are much more solid feeling, I have a few octals where the glue holding the glass to the base has failed and are now quite loose.
 

dougsta

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I fabri-cobbled 2 temporary adapters today, OCTAL plug to LOCTAL socket.

I pulled the 2 6L6GC from my Peavey Valveking 112 combo (50W 480vdc B+) and put these bad boys in, all good :)

Only ran it for 5 mins just to check it sounded ok, just to test !!not for long term use!! due to heat build up in the adapter causing insulation to fail.



IMG_8439.jpg
 




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