The AM Forum

Anyone have tube data for the OS51 tungsram tube? Its supposed to be a replacement for the AX-9909. I cant seem to find anything on them.

Clark

Haven't heard of those.  I have a Champ 300A that I replaced the AX 9909s with 8643s.  Gives about the same power and works fine.

AX 9909 is the same as the 6083, PE1/100, and OS-51.

http://tubes.mkdw.net/sheets/030/p/PE1-100.pdf

Id give serious thought to converting to 814/VT-154's which are a skinny predecessor to the 813. Cheap and readily available. Pretty much a sleeper tube.

Another that may fit is the 4D32 (its fatter) but I dont know how it will handle the HV.

Carl
KM1H

I changed my Chump over to a single 7094. It used the same socket but your will need to change a few connections on the socket. This is not a real common tube either but much more available than the 9909s. The 7094 will be loafing along in this service.

6083/AX9909, VHF pentode. Filament is 12.6 volts @ 1.35 amps. 45 Watts.
Hope this helps.
Regards,
Gary...WZ1M

I got the Tungsram os51s from the guy in bulgaria. It took a month to get them.  They where new as I cut the seals on the boxes.  I burned them in for a few hours and then loaded it up.  I get way less power output then the old AX9909s made.  ALOT less.  I wondered if I needed to alter the radio for the os51s.  They also pull more current. I get backswing on audio and a 50 MA dip in plate current with them.

Clark

I have a Glob Chump sitting in waiting for restoration. Like most of them it has a crack in the base of one of the 9909s from a zorch over. Knowing that these are made of unobtanium, I decided to look for a more commom replacement. Here is what I have come up with.

8643's these are the final tubes used in Motorola high powered lo band and high band Motrac mobile units. These tubes used to be very expensive at one time, but no one wants them anymore so now they are cheap and pretty plentiful.

They are kinda like a 5894 on steroids. they use the same socket as 9909s but the pinout is different (so you will have to rewire the sockets), and they have the plate pins out of the top. They also have 12v filaments and a higher dissapation rating than the 9909s.

Whenever I get started on that project, I will let everyone know how that works out.

                                                           The Slab Bacon

It works fine.  There was an article about changing the 9909 to 5894s some time back in Electric Radio.  Directions are clear and concise and when you finish you will have about the same power as the original tubes. 

I chose to use the 8643 because the voltage rating for the 5894 is only about 650 volts.  The author stated he had not had any trouble with them at that point, but the 8643 has a 750 volt rating.  The only things you will have to do is make some sort of plate cap for them and rewire the sockets like you mentioned.

I purchased a 4 ft. lenght of 1/4 thick aluminum rod at the hardware store.  I drilled holes for the tube plate pins and holes to allow #4 screws for tightning the cap to the tube.  The extra amount of mass the rod has helps cool the plate pins of the tube.

Another thing I did is find a small 115 VAC muffin fan approximately the size of the hole where the present fan is located and installed the muffin fan in place of the original.  The new fan is much quiter and moves a bit more air.

When you finish you should use 10 ma. grid current to get ~ 200 watts out on 75.  While inside I changed the load cap to a larger one and modified the tank circuit to give a match to 50 ohms on 160 meters, by using an L coil.  That required changing the bandswitch to one out of a DX 100.  That allows me to switch in the L coil on 160 and out on the rest of the bands maintaining a 50 ohm match on all bands.  The efficiency on 160 is a bit less but it still does just fine.

I have the AX9909's for my Globe Chump. I was told the secret to their longevity is to warm them up before throwing the plate switch. However, that is what I was doing when the LVPS T-1 decided to release its smoke, (an tar!). The fire co. was called because it filled the basement with smoke. How embarrassing.

yes, when the DERB-100 went out it did the same thing. how embarrassing.  ::) :P

The Globe Champ was a nice looking rig insie and out. I had a 300A for a while. I always thought the fan might have been aftermarket. Isn't the AX-9909 a cylindrical tube with two gold pins on the top? I think I seen some lately at one of the junk-vomiting places I been frequenting. Want me to look again? (might be a few weeks) but the price would be reasonable. You tell me what you want to pay new/used, I have no idea what they are worth. I always thought they were the modern version of the 829 but never explored.

The AX 9909 does not have a plate cap(s).  The 8643 is derived from the 5894 which was a cousin to the 829.  The 8643 plate pins are larger than the 5894 and the glass is much thicker.  Then there is the plate voltage difference.

One should be careful when putting the place caps on the 5894 and not twist the pins very much.  The glass will pop.  The 8643, or Motorola number is 97-136 A01,will withstand more abuse.  If you see them at hamfests, they are very good tubes.

Hey Slab:

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The Tungsram OS51 tubes that are on Ebay will work but they will not make more then 100 watts carrier with If this is ok for you then order them up.  At $60 each its not a bad deal.

I got some Amperex 6083s.  Popped them in and tuned the transmitter up to 300 MA. Got 150 watts out with .  Load it to the specified 330 ma and I get 175 out.. Amperex are the way to go in this transmitter.

Not sure why the OS51 is so low in comparison. But they do work.

Clark

Hi Clark and others , A good substitute would be a pair of 4D32 tubes. They are plentiful and come to life with 1000 volts on them . You will have more tube than the Chump can handle . You could get 300 watts outpoot on cw.
Have fun, Tim WA1HnyLR

I will look into that Tim.  A friend has a stack of 4D32s.  Can you see my Globe 300 Schematic post or check your email? 

THanks and nice talking to you the other night!

Clark
KE7TRP