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Author Topic: Early AL-800 SR#56  (Read 526 times)
N4JZY
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Posts: 15




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« on: December 27, 2009, 08:33:30 AM »

Hello

I have acquired an early AL-800 SR# 56 and I wanted to check and see if any one knows of any important updates (circuit updates over the years) I should make to the amp before I start with the second tube modification.

Thanks, Randy/n4jzy
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K6AER
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« Reply #1 on: December 27, 2009, 09:19:51 AM »

I’m curious why you are adding a second tube. Do you need more tube dissipation for RTTY service? The second tube does not yield much more power; maybe 200-400 watts output PEP. The AL-800 is really transformer/power supply limited as to the raw power it can produce as compared to the much larger AL-1500, AL-1200 that have a much larger HV transformer and support components.

If you have the tube and socket your not out much investment for the power increase. If you need to buy the tube which can cost $750 you would be much better to sell the amplifier and buy an amplifier capable of 1500 watts out with decent headroom.

A friend of mine just picked up an Alpha 86 that has a pair of 3CX800A7’s and a 3.5 KVA transformer for $1400. The amp is capable of 2300 watts PEP, 2100 watts key down and is not struggling at 1500 watts output. Bargains are out their in this economy.

Now I understand wanting to engage on a project and nothing is wrong with that. Understand after the amplifier is modified it will be worth maybe less in the eyes of the next owner.
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N4JZY
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« Reply #2 on: December 27, 2009, 09:44:55 AM »

"I’m curious why you are adding a second tube. Do you need more tube dissipation for RTTY service? The second tube does not yield much more power; maybe 200-400 watts output PEP. The AL-800 is really transformer/power supply limited as to the raw power it can produce as compared to the much larger AL-1500, AL-1200 that have a much larger HV transformer and support components."

Because I have a couple here collecting dust.

"If you have the tube and socket your not out much investment for the power increase. If you need to buy the tube which can cost $750 you would be much better to sell the amplifier and buy an amplifier capable of 1500 watts out with decent headroom."

I just need a few inexpensive components to make the amplifier capable of around 2200 watts out so it will only be loafing at around 1500 out with decent headroom.

"A friend of mine just picked up an Alpha 86 that has a pair of 3CX800A7’s and a 3.5 KVA transformer for $1400. The amp is capable of 2300 watts PEP, 2100 watts key down and is not struggling at 1500 watts output. Bargains are out their in this economy."

The 800 with a second tube will not be struggling to get 1500 watts out.

"Now I understand wanting to engage on a project and nothing is wrong with that. Understand after the amplifier is modified it will be worth maybe less in the eyes of the next owner."

It will be worth much more to me to be able to run 1500 watts with low drive.

I just need to see if there are any factory mods that need to be made while I am updating.

Randy/n4jzy
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W8JI
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« Reply #3 on: December 27, 2009, 02:56:20 PM »

Hello

I have acquired an early AL-800 SR# 56 and I wanted to check and see if any one knows of any important updates (circuit updates over the years) I should make to the amp before I start with the second tube modification.

Thanks, Randy/n4jzy

No. There are no significant mods.

I regularly run my AL800H at 1500 watts all modes, and it will easily do over 2300 watts on SSB or CW. Except for RTTY or sustained carrier operation, it will be tube limited. You are correct in your thinking.

I ran a single tube AL-800 amp on 6 meters at 1200 watts, and converted it to a pair. It can do near 2500 watts PEP and over 2000 CW now.  I would NOT run it at RTTY or FM any higher than a single tube would do, because it is transformer temperature and tank heating limited on RTTY or FM. It is NOT transformer limited on SSB or CW.
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N4JZY
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Posts: 15




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« Reply #4 on: December 28, 2009, 04:34:08 AM »

Thanks for the help Tom.

I will move forward in gathering the few items I need.
Hope you have a great New Year.

Randy/n4jzy
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