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Don Dulmage
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VE3LYX Ham Since 1980

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Other Callsigns
First issued VE3LYU

My Ham Radio Interests
Homebrew tubes CW and AM. Minimalist style.
Skeds for low power QSOs with homebrew stuff.

50C6 Cw rockbound with matching 12sn7 regen.
01 TNT 40M with matching 01 regen
40M hartley CW
80M x 40M Am transceiver HB
Two No 19 Wireless Sets
6l6 Breadboard Cw TX and matching 6sl7 regen.
BC454 recvr Operational 80M
ARC 5 T18 transmitter which now covers all of 80M band in CW and AM (cathode modulated through CW key jack)
Twin 811A HB linear Amp.

Other Interests
Speak Deutsch at a functional level, can get by in French but it is hardwork for me.
Make fiddles and play them. (gospel and country)
Drag racer . I run The Senior Dragster. Slant six powered.
I race it at Picton Airfield
Am a writer. I have two books published and many magazine articles in both the USA and Canada. I used to have my own opinion column in a local paper for several years.(View from the Ridge)
Cast aluminum for fun.
Also raised cattle for several years and trucked them. I also bought and sold for others. (Dolmetsch Beef Farm)

In the interest of allowing others to enjoy their clubs I now refrain from joining.(does not play well with others)

829B/3E29B linear amp


4/10/2013 8:52:40 PM (1 comments) Add a commentAdd Comment

I have a small linear I built for my hb transceiver. I use a 6146B or lately a 6293 in it. On my own I had been exploring for another tube. Reason being my DX60B also uses the same tube in its final and in poor conditions always comes up on the short side due to a lack of stomp. I wanted to try a 829B in Parallel pair mode and figured if I could get it to work I could just plug it into the 6146B socket. This stand alone amp seemed the place to test everything first. I got my tubes yesterday morning and picked out a 3E29B for the first experiment. First I made a dual plate to singe plate cap conversion. Next I found a old octal tube (a dead one) and liberated its base. I then took the 3E29b and joined its control grids and wired it for 6 volt heaters. The other pins I extended soldering wires to each pin. (Kathode, Screens Control grids and heaters. I fed those wires down through the octal tube base thru the appropriate pins and soldered them. I now had an octal based 3E29B that would plug right into a socket wired for 6146B I taped up the octal pins and the glass base of the tube then mixed up some kitty hair fiberglass. I filled the section where all my wiring was between the glass tube bottom and the octal tube base. 20 minutes later it was hard enuf to ruf sand then paint. Just before supper I unplugged the 6293 (Severe use pulse version of a 6146B (ceramic standoffs instead of mica) and plugged the 3E29B (Same deal to a 829B as a 6293 is to a 6146B)in the same socket. From the git go it worked well. It is a much better behaved tube. Why? I dont know. It just is.
Screen requirements were a bit different so I took care of that minor detail this morning. Power out is way up on the amp with the same PS as always running. It responds better to all controls then the 6146B style tubes. I will be testing it for the next few days on and around 7295kcs AM mode. Once I am convinced it is as good as it appears to be I will be making one up a bit shorter to pop in the DX60B.
After the fact I discovered this tube was used in some of the Viking 1 transmitters which gave me reason to think my idea wasnt so nutty after all.
Today I did a back to back test of the 6293 and the 3E29B. Allowing a complete tune of both tubes the 3e29B has significantly more output so in light of that I began making a very short version for my DX60B. I know I won't get DX100 performance but I now know for sure it will be signfcantly more then at present and somewhere between a Dx100 and a Dx60B and am figuring closer to the Dx100 then the DX60B. It is my hope this makes that little extra that will get me through the iffy QSOs when I am just there. I have decided to take this DX60B and fix everything about it that bothers me. If this tube swap works then look for a crystal socket on the front panel, a VXO switch and variable cap and an on-board VFO. Eventually a bit more plate voltage as well. Maybe 10 to 15% more. Also more C in the loading variable cap. Oh yeah! Proper coax and mic connectors too. I was going to buy a junker to do this too but couldn't justify that. I have this one and it is paid for. If I want an original later I can find one it seems easily.

Read the 1 comment after the break below.


by VE3LYX 9/17/2013 7:42:36 PM

This week took the amp apart and rebuilt it a a push pull. Seems quite strong. Am trying it on 7290 when I get opportunity. I also built a 811A GG amp . So far it has been nothing but a pain however It will eventually succumb to the relentless pursuit to get it working.
The ARC5 cathode modulation project has been completed and I have used it on the air successfully a couple of times.

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