Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mresistor on January 26, 2015, 09:22:52 am
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Was reading a previous thread about using a 7C5 for a 6V6. But, my question is, why wont a Loctal tube fit into an Octal socket? Is it the radius of the pins to center?
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Was reading a previous thread about using a 7C5 for a 6V6. But, my question is, why wont a Loctal tube fit into an Octal socket? Is it the radius of the pins to center?
It will, but the skinny pins don't make a reliable mechanical or electrical connection.
http://en.wikipedia.org/wiki/Tube_socket#Loctal (http://en.wikipedia.org/wiki/Tube_socket#Loctal)
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I see, thank you sir.
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If you held one in your hand you would see.
I believe a Loctal's pins are about the size of the things on a Miniature (12AX7), much smaller than the pins on an Octal 6L6.
Obviously the Loctal socket was designed to fit holes punched for Octal sockets, so existing chassis and tooling could be "upgraded" to Loctal at nominal cost (use-up your Octal bottles and sockets, re-stock with wonderful Loctal stuff).
A Loctal will NOT fall out of its socket. Airplanes, jeeps, etc benefited. You would think car-radios would, and some did, but many more clung to Octal. Price and diverse supply may have been part of the reason.
Out the garage I have a very odd radio. The "small" RF IF and 1st Audio tubes are large Loctals. The "power" output and rectifier tubes are 7-pin miniatures in sockets mounted in adapters to fit Octal/Loctal chassis punches. The 35mA final is 1/3rd the size of the 0.5mA driver. It's clearly transitional. Somehow they had an over-supply of RF IF Loctals, but needed to buy power tubes and the Minis were now cheaper even including the adapters.
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Thanks PRR - the Loctal info is all new to me.
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Here is a link to an adapter.
http://www.ebay.com/itm/291255853020?_trksid=p2059210.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/291255853020?_trksid=p2059210.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT)
I have used these, but most of the time I replace the socket. They seem high priced, but if you like NOS tubes the adapters really are not that expensive. Found a case of new sleeves of 5 at a Flea Market. 50 in all for the extremely high price of 50 cents each.
It is a great idea and very few actually do it I guess because the current production 6V6 is easy to get and they are making some good ones to boot.
I read about these. I believe a 41 plymouth had them in the radio. :laugh:
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A 1941 *anything* radio had them., esp Philcos. I always hated those tubes. I probably did not have the good removal technique, but every day I used to stop by the town dump on the way back from school. There were always between 1-4 TV sets and/or radios from which I took tubes and in many cases, transformers. I never bothered with the loctals. I always felt that they were sort of corroded into their sockets and that if I tried to snag them, one day I would tweak one of them too hard and end up with a thumb and finger full of shattered glass.
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you can get new ceramic loctal sockets, but they aren't very good quality. Of course, you can find some NOS loctal sockets that weren't good quality when they were new 60 years ago. socket choice is important. You'll read complaints about pin to socket connections (when cheap sockets are used).
Another small benefit of the loctal form-factor is they are a bit shorter than their octal counterparts.
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In case you don' t know this already - you don't need to pry them out of their sockets - you sort of tilt them in the direction the "nub" on the base is pointing and they pop out.
Prying will possibly damage the retaining clip in the socket.
Sometimes they do feel corroded in after 70 years though, so there's that, too...