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Author Topic: New tubes for 30L-1  (Read 709 times)

Posts: 68

« on: July 21, 2007, 05:01:07 PM »

Seems it's time to re-tube ol' faithful after 10 years, she's down to about 450 out. I sure will appreciate advice about what to use, 572B's look interesting. Brand names for top quality tubes and suppliers for best pricing sure will be appreciated. I haven't decided yet about the 572 change. I do have the new more powerful diode board installed. Hey, thanks, and 73..Dan K5PSO

Posts: 5639

« Reply #1 on: July 21, 2007, 05:21:46 PM »

Putting 572's in the 30L1 will only get you longer tube life. It will not get you a single watt increase in power because the power supply won't supply anything more to the 572s than the 811s.

There are a multitude of threads on the Amplifier forum on this exact subject. It will be helpful for you to read them before spending the extra on 572s.

Despite a lot of hype, the 30L-1 is a 500w amp, 600 tops, Don't try to make it something it isn't.


Lon - W3LK
Naugatuck, Connecticut

A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.

Posts: 5688

« Reply #2 on: July 21, 2007, 07:17:32 PM »

By far the best thing you could do for your old 30-L1 is to replace the filter cap board with one of Yves (Steve) Pautard, WN4I's upgrade versions.  Uses computer grade caps, new rectifiers.  Easy install in place of the old one.  Those old caps have got to be gettin' a bit tired by now.  

I did that to my 30-L1 back in the late 90s and it was a very cost effective and worthwhile thing to do.  

Also, you can use those 572b's in there, it is a very popular thing nowadays, but I don't recommend doing so because there is a fault situation that could happen where the 572's will likely take out the older components in your amp whereas the 811's are more likely to fail first, saving you money in the long run.  If someone comes along and argues against what I just said, remember, there will always be some of those around.  Its your amp.  arc-arc-arc-burn

4 new 8lls and spend the money on that filter board, man.  

You will be happy.


Posts: 1

« Reply #3 on: July 21, 2007, 07:19:07 PM »

572's have more plate dissipation which means a 572 will not work as hard to produce output than a 811. They should last longer but that is all you gain.  572 subs may also require more drive but I am not sure.


Posts: 9930

« Reply #4 on: July 21, 2007, 09:21:23 PM »

at ameritron you can buy 3 811's for $60.  or you could buy one 572 for $60.  I have yet to wear out the first set of 811's in any amp.  I actually have several sets of both 572's and 811's and even then I would use the 811's.  that is what it was designed for, and it works fine that way.

Posts: 497

« Reply #5 on: July 21, 2007, 10:38:02 PM »

I agree with N6AJR.  At twice the price it does not pay to buy 572's. 811's last a long time and will work fine at half the price.

Posts: 143

« Reply #6 on: July 22, 2007, 04:51:25 AM »

Reaching way back to the days when I had a couple of 30L-1's when you do replace the 811's I THINK you had to make sure you found replacements that were rated for horizontal service since that's the way they're mounted.  I could be all wet's been a long time!

Dino KL0S/4

Posts: 5688

« Reply #7 on: July 22, 2007, 08:22:25 AM »

The hidden problem inherent with replacing the output devices of any amplifier of any kind with devices rated for higher power dissipation than the original design is that the amplifier, which is nothing more than a modulated power supply, can get into real trouble under certain circuit fault conditions where the device itself would sacrificially fail before other more expensive components in that power supply can be damaged.  

I'd rather see you toast a relatively inexpensive 811 or two should that occur, and so should you.  

Those who think that using the 572 in place of the 811 will allow them to get away with long fumble-fingered tuneups without damaging tubes aren't thinking about what the long term excessive current and voltage demands may be doing to the mean lifetime of other components in the amp.  And those components plus troubleshoot/repair costs are going to exceed the cost of a new quad of 811s every time.  

*Practice tuning the amp quickly into the dummy load.  

*Use the dummy load for initial tuneup even when on-air QSY is what you are doing.

*Once amp is tuned (quickly) into dummy load, and exciter has already been used with antenna tuner to get the signal chain at or near the matching mark, switch from exciter-matchbox-antenna chain to exciter-amp-matchbox-antenna and do one quick tune of amp from that position and you are good to go.  

*Use the RF Power Output control of the exciter to best advantage.  Setting the exciter to ~50 - 70W output and leaving it there not only ensures that the overdrive condition will most likely never occur, making you a cleaner operator on the bands, but can and will increase the MTBF of amplifier components, to include the tubes.  The S meter at the other end won't fall enough to be a factor.  

***  Replacing that old power supply capacitor board with the WN4I usually makes a BIG difference in the health -- and PEP output -- of an old 30-L1!!! ***

Adding that board and using a good quad of 811s (yes, designed for horizontal installation) will likely make you think you've unpacked a new and different amp.  

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