Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Oddvar on December 16, 2022, 12:34:57 pm
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Might be the wrong place this, but I wonder if anyone could tell how to turn a 5840 tube into a triad, I need to know how the eight pins can be connected to: anode, H+, H-, gate and cathode? Eight pins into five points. I have looked everywhere, but info is a bit vague. Best advice so far is in the pic, but I am in the dark. Some say one shouldn't kee pins unconnected, if so, who should go where?
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This tube has wire leads instead of pins. It does not plug into a tube socket.
(https://www.adorama.com/images/Large/tfef7325840.jpg)
Lead 1 connects to the grid circuit.
Lead 2 connects to the cathode circuit. Just tape off leads 4 and 8 since they are internally connected to lead 2.
Connect leads 5 and 7 together. This makes the tube a triode. Connect the two leads to the plate circuit.
Connect leads 3 and 6 to the 6.3V filament supply.
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Great Sluckey, thank you ever so much.
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This tube has wire leads instead of pins. It does not plug into a tube socket.
But can and do have sockets specifically for them.
https://www.dropbox.com/sh/u690mpdw8qxiqid/AAAPv8EpvgAJnfk5NznxyMbza?dl=0
They (sockets) are scarce and are a pain to solder to - Typically I use 24-26AWG solid core teflon insulated wire. Those pics are of a pedal I was working on. Two 6788 pentodes and a 6948 dual hi-mu triode. Power is provided by a wall-wart to a 5W DC-DC converter supplying ~200VDC for the B+ rail. Wall wart provides 15VDC@3A and we regulate 6VDC for filaments with a 7806 linear v. reg.
--Pete
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On e-bay you can find this to simplify your life
https://www.ebay.com.my/itm/201105035628 (https://www.ebay.com.my/itm/201105035628)
(https://i.imgur.com/CSQ4wnP.jpg)
(https://i.imgur.com/YO4oofJ.jpg)
(https://i.imgur.com/cbwL9Me.jpg)
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Also this is an option but, can I say, expensive
https://www.ebay.it/itm/175204203602?chn=ps&norover=1&mkevt=1&mkrid=724-128315-5854-1&mkcid=2&mkscid=101&itemid=175204203602&targetid=1827389197184&device=c&mktype=pla&googleloc=1008894&poi=&campaignid=17955385566&mkgroupid=142692416071&rlsatarget=pla-1827389197184&abcId=9301109&merchantid=116379287&gclid=CjwKCAiAy_CcBhBeEiwAcoMRHLZYQw9-CKZkK2i8XtmnvtpxQVrbllDn7dlnroplu5-S0Xp6Ubp6xhoC7hcQAvD_BwE (https://www.ebay.it/itm/175204203602?chn=ps&norover=1&mkevt=1&mkrid=724-128315-5854-1&mkcid=2&mkscid=101&itemid=175204203602&targetid=1827389197184&device=c&mktype=pla&googleloc=1008894&poi=&campaignid=17955385566&mkgroupid=142692416071&rlsatarget=pla-1827389197184&abcId=9301109&merchantid=116379287&gclid=CjwKCAiAy_CcBhBeEiwAcoMRHLZYQw9-CKZkK2i8XtmnvtpxQVrbllDn7dlnroplu5-S0Xp6Ubp6xhoC7hcQAvD_BwE)
(https://i.imgur.com/WsbM8by.jpg)
Franco
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Connect leads 5 and 7 together. This makes the tube a triode. Connect the two leads to the plate circuit.
perfect timing for me as I am triode strapping a #78 pentode and 6A7 pentagrid (still have two grids on this one to deal with)
I have read that if you add a 100R between screen and plate it works better because it prevents parasitic oscillations, whatever that is :-) http://www.audiodesignguide.com/New2A3/ETF06TS.pdf
also, Can we use the same pentode curves for setting bias when operating as triode?