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Heathkit SB200 tubes getting red

Jimbo165 said:
Why does a SB200 with two 572B's with 320w dissipation make only 640w output when a D&A Phantom with 10 6LQ6 tubes equaling 300w dissipation make 1000w output with a 4w drive. The Phantom has less total dissipation. Tubes in a SB200 will take a 300w drive because my brother has been doing it to his SB200 for over a year now with same tubes no major problems and he is getting a lot of contacts that a 640w amp would not be able to get he uses his to talk skip on channel 17 and 28. He knows the tubes are not going to last but that is why he chose the SB200 two tubes are cheaper than 10 like in my Phantom. There are a lot of people out there pushing their amplifiers well past design limits sure they will break but they will tell you the reward is worth the pain. I do not plan to drive my SB200 like that I mainly bought it to use on 38LSB but still wanted maximum output but have plug in the wall pill amps that can do almost the 640w output of Heathkit so may sell the SB200 a lot of people in my area that have heard it on air and want it already. I hope I can still count on all the great help this forum has given me . Thanks Jimbo165
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The 6LQ6 has a 30 watt continuous plate dissipation without forced air cooling. That goes up with the fan and for intermittent applications. That was the good news on the Phantom. The bad news is there are not 300 watts of dissipation making the 1000 PEP. As I recall there are only 6 tubes in the final stage of this amp so the output dissipation is a mere 180 watts.

It takes a while to accept that twice the output is not worth 25% of the tube life or that when the tube turns red you're beating the snot out of it. It gets much easier to run a linear properly once you realize twice the power amounts to virtually nothing in terms of signal strength and everything regarding spectral purity, tube life and amplifier reliability.

PS: If you think you can drive the Heathkit this hard because the tubes are cheap, the only part I can agree with is that the tubes are cheap and that's the biggest reason not to overdrive them. There are no quality glass tubes for RF applications being manufactured today. Since Eimac and Amprex closed the glass production down, you can't buy a good 3-500Z anymore much less a 811A or 572B. They haven't been any good since RCA and Cetron stopped making them.
 
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you can't buy a good 3-500Z anymore....
Best I've found Were Machlett (Penta) at least they seem OK(Tested Stateside before shipment). I actually see "slightly" more output from them than I do the Eimac's(I have 5 pairs I rotate) or the Amprex ZG's(strongest tubes ever but do require little more drive) Last NIB set I found I paid $425.00...Seller had 2 sets I should have bit the bullet and Paid the $900 for both NIB sets!:oops:

much less a 811A or 572B.....Svetlana were the last good ones...but now more or less same price as RCA or Raytheon's(Cetron's/Slyvania's)
All the Best
Gary
 
359 said:
100w into four 572b's making 1200w is 11dB and sounds about right. 100w into two 572b's making 600w is only 8dB and doesn't sound right. So my question was, "how does adding tubes increase gain"?
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I think you know adding tubes does not increase gain. The difference in output is effected by a few things. First the Dentron manual says it can take up to 150 watts of drive where the SB-200 maxes out at 100. I think the Dentron uses a slightly higher plate voltage too. Lastly, the 572B has a drive impedance of 200 ohms. Four of them together make an efficient 50 ohm match to the exciter before any input tuning.
 
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I didn't see anything yet about the capacity of the power supply. You can stick a couple dozen tubes in there, but if the power supply isn't up to the task... :(

Reminds me of the piano teacher who wanted to move his huge concert grand piano up a long flight of stairs. He hitched his little kitten to the piano with a piece of rope. When his guests gasped and protested that a kitten couldn't possibly pull a 2500 pound piano up stairs, the teacher said, "Why not? I have a whip, don't I?"
 
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Shockwave said:
I think you know adding tubes does not increase gain. The difference in output is effected by a few things. First the Dentron manual says it can take up to 150 watts of drive where the SB-200 maxes out at 100. I think the Dentron uses a slightly higher plate voltage too. Lastly, the 572B has a drive impedance of 200 ohms. Four of them together make an efficient 50 ohm match to the exciter before any input tuning.
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I take it comparing a Dentron and a Heathkit is like comparing apples and pears and has little to do with 4 tubes vs 2 :D
 
Beetle said:
I didn't see anything yet about the capacity of the power supply. You can stick a couple dozen tubes in there, but if the power supply isn't up to the task... :(

Reminds me of the piano teacher who wanted to move his huge concert grand piano up a long flight of stairs. He hitched his little kitten to the piano with a piece of rope. When his guests gasped and protested that a kitten couldn't possibly pull a 2500 pound piano up stairs, the teacher said, "Why not? I have a whip, don't I?"
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Captain Kilowatt said:
Ok Jimbo, first off this is not meant to be derogatory but you obviously do not understand a few things. First, an amp that makes 1000 watts will not make generally contacts that an amp making 640 watts cannot. There is less than one half of an S- unit difference between 640 watts and1000 watts. That is a simple law of physics that cannot be broken. I have switched power by 10 times and hardly made a difference. There are times when running on the ragged edge where it will make the difference between making contact or not but those times are quite rare. The other thing is tube life. I already mentioned about what CBers do to amps in the quest for more power and you pretty much confirmed that by saying about the shortened tube life. The other BIG thing not yet mentioned about the Heath amps is that the power supply is not capable of providing enough current and voltage to run those tubes much beyond 600-700 watts. Heath amps have never been known for having beefy power supplies even in the 3-500Z amps.572B's really like to see about 2400 volts on them and IIRC the SB200 runs less than 2000 and has small wire on the transformer which limits current to a point in which you start to see excessive voltage drop when you try and push the crap out of the amp.
As for the D and A or whatever making more power with less dissipation, well I would like to see it at 1000 watts versus the Heath at 640 watts on a spectrum analyzer and oscilloscope. One will be vastly cleaner than the other whether someone on the receiving end realizes it or not. Most people cannot tell when something sounds good or when it sounds GOOD. Most equate good to being loud and if it splatters all 40 channels then it must be putting out a lot of power and working good. I have even heard people telling loud distorted signals that they sound GREAT! Signal strength isn't everything.
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You missed it. :D
 
Radio Tech said:
Well lets just remember that 2 572B's will produce about 600 watts tops in the safe zone with 100 watts of drives. 4 you give you 1200 watts out with 100 watt drive. In thero...unless you hammer them to death.

Now, 572B's give you 160 watts dissipation per tube, so with 4 you have 640 watts dissipation total. The SB200 only has 2 tubes. So do the math...
I get SB200's, SB220's, and drakes in the shop all the time. The biggest killer in these amps are the power supply. They are just too small and will not supply enough current to run them.

I really hate to say this but I will. A lot of folks think that a 100 watt device, say like a 2SC2879 will produce 200 to 300 watts. Because they see it on the meter. This is bull. And the same goes with tubes. What folks fail to see in these claims is most "CB" style watt meters do not know the difference from the on frequency power dissipation and harmonics. The meter simply adds them all together.

If you take a radio with a 12 watt final and tune it to get 25 to 30 watts out of it it has to be louder right? NO, it is distortion and the meter combines it all together.
Ok, I will shut up on this now.
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Everyone missed it from page 3 :p
 
SB200 tubes getting red

Thanks guys for all the comments they are not falling on completely deaf ears I have admitted I am in a learning curve just did not know it was Dead Mans Curve LOL. I will admit that I am a Cber starting out and it was what brought me back into radio 3yrs ago after being out of it since 80s the fun of skip talking and local power wars for sure. It may not mean a lot in the distance going from 640w to 1000w but 30 miles away during one of our local power fun nights which we have about 14 people involved sometimes it has made a definite difference on getting over the others that one S unit can be the difference in being heard or not. I guess most of you have been Hams and never talked skip so it is understandable why you would want perfection in contacts or sound of your station and skip is your enemy but when I first got into radio in 1972 there was skip and now 2014 it is still here and still kinda fun too.I am now slowly getting out of that and getting into sideband. I like being able to have a decent contact and able to have real conversations with new contacts everyday. I apologize for being rude and still hope to enlist your help with my projects now and again. Administrator if possible please delete entire post Thank You
 
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Jimbo165 said:
Thanks guys for all the comments they are not falling on completely deaf ears I have admitted I am in a learning curve just did not know it was Dead Mans Curve LOL. I will admit that I am a Cber starting out and it was what brought me back into radio 3yrs ago after being out of it since 80s the fun of skip talking and local power wars for sure. It may not mean a lot in the distance going from 640w to 1000w but 30 miles away during one of our local power fun nights which we have about 14 people involved sometimes it has made a definite difference on getting over the others that one S unit can be the difference in being heard or not. I guess most of you have been Hams and never talked skip so it is understandable why you would want perfection in contacts or sound of your station and skip is your enemy but when I first got into radio in 1972 there was skip and now 2014 it is still here and still kinda fun too.I am now slowly getting out of that and getting into sideband. I like being able to have a decent contact and able to have real conversations with new contacts everyday. I apologize for being rude and still hope to enlist your help with my projects now and again. Administrator if possible please delete entire post Thank You
Click to expand...

Power change is power change and does not matter if the other station is two miles away or two thousand miles away. The signal difference is the same, still less that one half of an S-unit.Will it make the 1000 watt station able to be heard over the 640 watt station....yes barely however it will not make it stand out head and shoulders above. As for the suggestion that we hams, yes I said WE because I am one of almost 30 years, never talked "skip" again shows a disconnect. That is what 99% of hams do.....talk "skip". Unless I misread you and you were trying to be sarcastic you are clearly wrong in that assumption.What you call "skip" on AM CB does sound like pretty much noise while on SSB that solid rush of noise is considerably different. SSB is far easier to talk "skip" on and is generally the preferred mode of hams wanting to communicate around the world.
 
Jimbo165 said:
Thanks guys for all the comments they are not falling on completely deaf ears I have admitted I am in a learning curve just did not know it was Dead Mans Curve LOL. I will admit that I am a Cber starting out and it was what brought me back into radio 3yrs ago after being out of it since 80s the fun of skip talking and local power wars for sure. It may not mean a lot in the distance but 30 miles away during one of our local power fun nights which we have about 14 people involved sometimes it has made a definite difference on getting over the others going from 640w to 1000w , one S unit can be the difference in being heard or not. I guess most of you have been Hams and never talked skip so it is understandable why you would want perfection in contacts or sound of your station and skip is your enemy but when I first got into radio in 1972 there was skip and now 2014 it is still here and still kinda fun too.I am now slowly getting out of that and getting into sideband. I like being able to have a decent contact and able to have real conversations with new contacts everyday. I apologize for being rude and still hope to enlist your help with my projects now and again. Administrator if possible please delete entire post Thank You
Click to expand...

Wow! There is some much special material in this one post...
OMG(y)
All the Best
Gary
 

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