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Author Topic: Amplifier Tubes  (Read 657 times)
W8RID
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Posts: 45




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« on: December 09, 2008, 01:20:46 PM »

I have just been given a Drake L-4B Amplifier. (yes given)
It is very clean and had been used up until about 2 months ago.

I know the person who gave it to me and take his word as gospel.

Is there a way or how do you check the tubes to see if they are "Matched" or if they need to be replaced?

Bob
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W1QJ
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Posts: 1446




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« Reply #1 on: December 09, 2008, 01:28:06 PM »

Take the amp, set it up with your radio and test it out with the tubes.  if the tubes are good the amp will perform as it should.  The tubes really do not need to be matched, it will work even though they are not.  Give it a try and see what happens.  If the amp was working OK 2 months ago, it should still be OK now.
Good Luck
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WB2WIK
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« Reply #2 on: December 09, 2008, 01:59:13 PM »

Drake didn't ship them matched, so why would they be matched now?

WB2WIK/6
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W8RID
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« Reply #3 on: December 09, 2008, 02:47:44 PM »

I was just going by what I have read about amplifiers and the tubes in them. Everything I have read says that you should have matched tubes.

Bob
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WB2WIK
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« Reply #4 on: December 09, 2008, 03:01:36 PM »

That's the problem with the internet.  Someone starts a rumor, it spreads like wildfire, and then becomes fact.

I had an L-4B when it was brand new, and Drake did not supply them with "matched tubes."

I don't know of anyone making dual 3-500Z amplifiers that does supply them with matched tubes.

WB2WIK/6
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WB2WIK
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« Reply #5 on: December 09, 2008, 03:04:27 PM »

BTW if you don't have the L-4B manual, you can download it here:

http://wb4hfn.com/DRAKE/DrakeManuals/L4B/Manual_L4B.htm

You'll note under "SERVICE" that Drake simply recommended if you need to replace one tube, please use the same type tube!  (That is, don't mix a 3-400Z with a 3-500Z.)  Nothing at all about "matching."

WB2WIK/6
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VR2AX
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« Reply #6 on: December 09, 2008, 06:01:37 PM »

If you look at page 22, they might also be saying not to mix an Eimac with an Amperex tube, or potentially any of the subsequent manufacturers that produced the tube after the manual was first printed (c. 1968).
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W8JI
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« Reply #7 on: December 10, 2008, 03:51:34 AM »

Not only do the tubes not have to be "matched", most people selling matched tubes lie about them being matched.

The tubes should probably be the same brand, and they should both be good. I wouldn't mix an Eimac with a Chinese tube. But as long as they are somewhat similar in characteristics everything will be fine.

Change all your valve stems when your tires are changed. Change your air filter, and spark plug and wires at 36k miles for better fuel economy.  Match your tubes.

Don't expect to see me do that silly stuff.

The air filter, and this is a fact, can almost totally plug with no change in fuel economy. All you lose is open throttle power because the airflow is restricted to low volumes, the mixture is unaltered in a modern engine because it has a mass airflow sensor for mixture. As a matter of fact if you are a lead-foot the economy goes UP with a plugged filter.

matched tubes are the same bull$%$#  A dishonest way to get money.

73 Tom.
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VR2AX
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Posts: 589




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« Reply #8 on: December 10, 2008, 05:04:53 AM »

Absolutely right Tom, a modern practical application of Heisenberg's uncertainty principle.

VR2AX
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KE4DRN
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Posts: 3722




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« Reply #9 on: December 10, 2008, 03:18:53 PM »

hi Bob,

One thing you can do is to check the
neturalization of the tubes in your amplifier.

not all classes of amplifiers require
a matched set of tubes.

73 james
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