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Old 23rd Apr 2017, 8:04 am   #21
G3VKM_Roger
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Default Re: Acorn valve 954 kits 1960's

Quote:
Originally Posted by M0FYA Andy View Post
I think that soldering directly to the pins is a bodge, and looks like a bodge, even if low temperature solder eliminates damage.
Modern aircraft circular connectors use removable pins and 'socket pins', I have some scrounged during my working life. I wonder if they are readily available?
Andy
Years ago I built an acorn valve RX and used a wafer from a redundant multi-wafer rotary switch (with the centre rotary contact disc removed) as the valve holder. ISTR that I moved a couple of the contacts on the wafer to align with the acorn pins. I now have a large box of similar switches, so perhaps I should re-purpose them as acorn holders

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Old 23rd Apr 2017, 9:17 am   #22
M0FYA Andy
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Default Re: Acorn valve 954 kits 1960's

I've been pondering on this, and wonder if a solution might be to modify a genuine holder's clips so that rather than gripping the pins they just sit on a contact pad, maybe with a locating groove. Then mount an annulus of PTFE or other insulating material above to clamp the pins down. The screws used to hold the valveholder in place could be lengthened to also serve as clamping screws.
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Old 23rd Apr 2017, 9:52 am   #23
G3PIJpeter
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Default Re: Acorn valve 954 kits 1960's

Has this one been suggested before - wirewrap the pins and solder the free ends to bolted or riveted tags surrounding a circular cut-out in a paxolin board . . . ? My TS830S has been working for over 30 years with all the boards connected with wirewraps around pins.
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Old 23rd Apr 2017, 10:07 am   #24
Phil G4SPZ
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Default Re: Acorn valve 954 kits 1960's

My memory may be playing tricks on me, but I vaguely recall seeing an Acorn valve socket where the valve was inserted using a 'push-and-twist' action. But I may be wrong.
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Old 23rd Apr 2017, 10:58 am   #25
G4XWDJim
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Default Re: Acorn valve 954 kits 1960's

Looking at the style of connectors in this Acorn valveholder confirms the idea that considerable pressure evenly placed is necessary to push the pins into the tight fitting clips.

The pins are steel with some sort of plating that doesn't always seem effective at preventing corrosion. Whatever connectors are used they seem to need some 'bite' to maintain a good connection

I've never come across one making a bad connection although the valve itself does have a reputation for losing its vacuum.

Jim
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Old 30th Apr 2017, 11:02 am   #26
David G4EBT
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Default Re: Acorn valve 954 kits 1960's

The valve does need some pressure to force the pins into the clips, but the clips do make excellent connections. Easiest way to get the valve into the holder is with pressure from thumbnails. For homebrew, apart from the fact that the valve-holders aren't easy to come by, I think it's no more of a risk to the valve make wire soldered connections to the pins. It isn't difficult if a little wire coil is formed around a 0.8mm drill bit shank and small pliers used as a heat sink when the joint is quickly soldered. Another option is to use small screw terminals from terminal strips. Some pics attached.

The acorn valve which has a 1.25V 0.1A heater (rather than the usual 6.3V 0.15A heater of the 954/955 is the 958A triode, which came out in 1944 and was used by the Air Ministry. Remarkable little valves which work up to 350MHz. There used to be lots around - I bought a box of five some years ago. Not quite as versatile as the pentodes, or as plentiful nowadays. I'm not sure if the 1.2V heaters would be happy with a 1.5V cell, but rechargeable cells are I think generally 1.2V.

I have a half-built 3 valve Acorn Receiver project in which the valves are hard wired, which featured in Short Wave Mag many years ago. I made the cabinet, wound the coils for the coil pack, then it stalled. Forum member Peter Sables got on with his yonks ago and built it - mine is still 'work in progress' - on my 'half-done list' rather than my 'do list'. It's a familiar tale!
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Old 6th May 2017, 12:46 pm   #27
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Default Re: Acorn valve 954 kits 1960's

I have a friend with a radio shop in Japan who's now selling VHF kits with Acorn valves. Will try to get him to send one over for evaluation.
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Old 8th May 2017, 11:14 pm   #28
Radio1950
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Default Re: Acorn valve 954 kits 1960's

For 954/955 connections, we stripped down 7 and 9 pin valve sockets, and used the inserts as push-on connectors.
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Old 9th May 2017, 3:11 am   #29
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Default Re: Acorn valve 954 kits 1960's

Memory is quite dim, but I recall my little one-acorn - the acorn was a push-fit into a rubber grommet and all the connections were made by push-on clips. I only had the 49m coil but that was enough in the mid to late 50's. I think I ran the filament from one of those flat 4.5v cycle lamp batteries and a 22.5v hearing aid battery for the HT.
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