Kris Power Pump Linear Question

[broncoman529]

Today my Kris Power Pump Linear was working just fine(150w on AM and 280w on SSB. Well I have had it for only one day and one of the tubes(I think) went bad and it stopped transmitting(I was only driving the linear with 1.5- 2 watts). Well I am going to replace the two driving tubes with a matched pair of 6LQ6/6JE6c's. What I want to know is what is the third tube for? Also I would like to replace the third tube(It is behind a metal heat shield),But I do not know what the tube identification number is(It has been rubbed off). Does anyone have a clue what the identification number of this third tube is? Please let me know, If anyone knows where I can find a schematic online please let me know. Is there a direct replacement tube that can be used with this linear other than the 6LQ6/6JE6C's, Maybe tubes that are still manufactured or readily available? Tube linear experts, Please chime in :Thumbup:

Thanks,

Larry T.

 

[nomadradio]

Hi Larry,
The short "baldy" tube, the one with no metal cap on the top, is type 12KV6A. This is the rarest of the rare. Possible sub is type 12JT6, but its power rating is smaller.

It's the driver stage. Unless your radio is pretty small, this tube works pretty hard. A "10-meter" base radio with two final transistors is probably too large for this box. The 'input match' on this box is not all that good. A SWR meter placed between the radio and the PowerPump will show around 3 to 1 when the amplifier is keyed.

The two larger tubes are the final stage. This model does not place any operating-bias voltage on the tubes, and they tend to overheat. Adding bias will help, but there are no "DIY" procedures for that on the web that I'm aware. If you had looked inside before it failed, you would probably have observed the tubes "cherry up". The gray plate structures you see just inside the glass envelope should stay dark while it's transmitting. If they begin to glow dull red, then steadily brighter, that tube will fail VERY soon. The plates on those tubes should stay dark, to prevent damage from overheating.

These tubes have not been made for over 15 years, more or less. If there were a good, effective substitute, they would be just as rare as the original types. As the years go by, the supply dwindles steadily, and the price just creeps ever upward.

73

 

[broncoman529]

I really appreciate your help. Maybe I burned up the driver tube using my Doc tuned HR2510. I never realized that the drive mattered, I always thought it was the amount of watts you put into it that mattered, Thats why I was only using 1.5- 2 watts. The 6lq6's were flashing blue inside while I was modulating on them on SSB, But the plates were not glowing and they were dark as you said they should be. I think it may be the driver tube then, So I ordered two of the 12KV6A from http://www.onlinecomponents.com and they were only $17.11 a piece. How did you know what driver tube I have in my Kris Power Pump? Do you have a schematic or do you actually have the same linear I do? I would love to get a copy of the schematic/Instructions if you have it. I went to the CB Tricks website and they have the schematic, But it did not show the actual tube types on the schematic. Hopefully you have a more accurate diagram. Please let me know. Again I really appreciate your help.

UPDATE: My wife talked to the guy who is testing my 6LQ6 tubes and he said they are very weak. I need to talk to him, But my wife said that they both tested around 2700 and that they should be around 7800 whatever that means. I will talk to him tommorow. I also need to give him the driver tube number so he can test it.

 

[CDX126]

Try Allen ( Fixer) at TubePlus.com he should be able to get you schematics and hook you up with some king of instructions for your amp. Also, those tubes ( 6lq6) are rather expensive, you might want to talk to him about a tube conversion or just getting new 6lq6 tubes he might be able to hook you up.

 

[broncoman529]

http://www.tubeplus.com is not working. Is the address right?

 

[nomadradio]

Uh, there's a letter "s" in the middle of www.tubesplus.com

See if that works any better.

The diagram is posted free at www.cbtricks.com. Click on "Amp Info" up top, then on "Kris" in the sidebar window. Both GIF, JPG and PDF versions are currently there to download.

It doesn't say which tubes are used on the schematic, that was from memory. The larger, and more expensive 6MJ6 version of the final tube tends to last longer, but they are harder to find every year that goes by. The 6LQ6 is a bit less stout, but cheaper and easier to come by.

The HR2510 only has one final transistor, but it's rated for just about exactly twice what the final used in a legal 40-channel CB delivers. That radio is kinda large for that amplifier.

One thing that is likely to help is called a "swamping" resistor. It gets placed in parallel with the input to the driver tube. The radio's drive power is split between the resistor and the driver tube, reducing the strain on it.

For that model, it takes more than just a resistor. You need a capacitor in series with it.

A 500-Volt or 1000-Volt ceramic disc capacitor, .05 uf or .047 uf, more or less, gets one lead to pin 3 on the driver tube's socket. One end of a 100-ohm 5-Watt (NOT wirewound) resistor goes to the free end of the disc cap. The other end of the resistor goes to ground, preferably near to the driver socket.

This also brings down the input SWR that you'll see on the radio's internal SWR meter. A 68-ohm or 82-ohm resistor may bring the input SWR down a bit more, but you'll need to use a larger size than 5 Watt if you reduce its resistance value below 100 ohms.

The date on the schematic is 1971. When that amplifier was designed, a "normal" tube-type CB would push a 3 or 3.5-Watt carrier, and no more than 16 or 18 Watts peak on AM modulation. Solid-state radios in 1971 seldom showed more than around 14 or 15 Watts PEP on SSB.

The 2510's transmitter is roughly twice the size of a 'normal' early-70's 23-channel CB radio.

The 2510 by itself delivers nearly as much as the driver tube does, feeding the two finals. Somebody (else) should post a "bypass" procedure to eliminate the driver tube. It would probably give you 75% or 80% as much with the 2510 driving the two finals directly, as it does with the driver tube.

73

 

[broncoman529]

Well, I have a matched pair of 6mj6's coming in the mail from http://www.vacuumtubes.net I also have those 12KV6A driver tubes coming from http://www.onlinecomponents.com All of my tubes should be here on Monday hopefully. I heard that I should leave the amplifier on standby for 10 hours before trying to tune or load the new tubes(Break in), Is this true? I will try to post a picture of my two tube amplifiers once everything is up and running. I have a Courier ML100 tube linear that I love to use also, I always get great radio checks on that :shock:

 

[nomadradio]

Well, uh, (ahem), looks like I screwed up.

Larry pm'ed me to say that the heater on his driver tube was really dim, and wouldn't deliver power.

I checked the schematic at www.cbtricks.com, and sure enough I was wrong. It doesn't mention the tube types on the diagram, but it DOES show all three tubes' heaters wired in parallel. That means that the (correct) driver has a 6.3-Volt heater like the two finals, and NOT the 12.6-Volt type that I told him he'd need. Oops.

Since other folks read these, I'd like to set the record straight before somebody else takes my wrong advice with a Kris Power Pump.

The correct driver tube is the 6.3-Volt version. Originally it was probably a 6JT6. This tube has a smaller power rating than the 6KV6 and tends to wear out sooner.

But either one, 6JT6 or 6KV6 will work in his Kris Power Pump, and NOT the 12.6-Volt version that I (erroneously) told Larry in the previous post.

Jumped the gun, without checking first.

On the other hand, there's no guarantee that ALL of the "Power Pump" boxes made by Kris were built with the same transformer. I know we've seen at least one that used a 12.6-Volt winding, feeding that voltage to the driver heater, and with the two 6.3-Volt final heaters wired in series. Could be someone replaced the original transformer, or could be that they made more than one production version. Don't know. Going by memory alone wasn't as smart as checking first would have been.

I DO know I steered Larry wrong on this one. My sincere apologies to anyone who may have been inconvenienced.

73

 

[broncoman529]

No problem, I will just throw those 2 12KV6A's up on ebaY unless someone needs them here Should I go with a 6JG6A driver tube like the Kris Power Pump in the ebaY ad? Or do you think I should use either the 6JT6 or the 6KV6 as you suggested? Please let me know.

Thanks,

Larry T.

 

[nomadradio]

The reason I keep mentioning the 6KV6 is because they last longer. The other types will deliver about the same power in this model, but because they all have lower power ratings, they will work harder to do the same job. One very good rule about power tubes also applies to most other machines. Works harder = Fails sooner.

You won't usually see a significant power difference between that one and the other compatible tube types for that spot.

I appreciate you being a good sport about the bum steer. Just goes to show it pays to take aim before squeezing the trigger.

73

 

[Buddy 2020]

Hi Larry,
The short "baldy" tube, the one with no metal cap on the top, is type 12KV6A. This is the rarest of the rare. Possible sub is type 12JT6, but its power rating is smaller.

It's the driver stage. Unless your radio is pretty small, this tube works pretty hard. A "10-meter" base radio with two final transistors is probably too large for this box. The 'input match' on this box is not all that good. A SWR meter placed between the radio and the PowerPump will show around 3 to 1 when the amplifier is keyed.

The two larger tubes are the final stage. This model does not place any operating-bias voltage on the tubes, and they tend to overheat. Adding bias will help, but there are no "DIY" procedures for that on the web that I'm aware. If you had looked inside before it failed, you would probably have observed the tubes "cherry up". The gray plate structures you see just inside the glass envelope should stay dark while it's transmitting. If they begin to glow dull red, then steadily brighter, that tube will fail VERY soon. The plates on those tubes should stay dark, to prevent damage from overheating.

These tubes have not been made for over 15 years, more or less. If there were a good, effective substitute, they would be just as rare as the original types. As the years go by, the supply dwindles steadily, and the price just creeps ever upward.

73

It is a 6kv6