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Ameritron's 3CX1200Z7 or 3CX1500A7 for my Johnson Viking Ranger II




 
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Author Topic: Ameritron's 3CX1200Z7 or 3CX1500A7 for my Johnson Viking Ranger II  (Read 2467 times)
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WD4DMZ
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« Reply #25 on: February 01, 2018, 08:21:47 PM »

Fortunately I saved my original AL80 file. I did in fact do the meter mod and replaced the 100k resistors. Also changed the plate cap in addition to lowering the tube socket. There was also a new fan resistor and some sort of bracket added.

It would appear my AL80 is up to spec.

Just now checked the output with 10 watts in...

120 watts out with 2,400 plate V and 220 ma current equals 528 watts input.

Rich
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #26 on: February 01, 2018, 08:38:34 PM »

I use a few guidelines regarding plate dissipation and power output that will roughly estimate power parameters on AM and ssb:  (Linears)

(This assumes adequate cooling.  Plate voltage will also affect these estimates)

1) Power out on AM -  The ABSOLUTE maximum AM carrier output for a tube (in linear)  is  the plate dissipation /2.75 and preferably lower.   So, a pair of 3-500Zs should not be run at more than 363 watts out.   1000/2.75

2)  Carrier vs: PEP -   Take the maximum power out /6  to set the AM carrier level to allow for pep audio power out with headroom and cleanliness.  Thus, a pair of 3-500Zs that put out 2KW maximum (pep) should be run at about  2,000 / 6 =  333 watts max carrier.

3) SSB PEP -  A good running SSB amplifier pep power out generally runs about the plate dissipation X 2.  Thus, a pair of 3-500Zs should be good for about 2KW pep out.  1KW dissipation X 2 = 2KW.

4) Class C AM plate modulated:  Take the dissipation X 1.4  to arrive at the carrier output.  For example, a pair of 4-400As at 800W dissipation will do 1120 watts AM carrier.   800W X 1.4 = 1120W.     Or, a single 6146B  at 35 watts dissipation will do 49 watts AM carrier out at max.  35W X 1.4 = 49W.


Use these guidelines on other tube line ups and you will see it works out reasonably close.  However, there at anomalies... 813s at 125 watts dissipation are actually more rugged, more like 175 watt tubes  and can withstand a little more.   4-1000As are also more rugged than specs say - more like 1500W+ plate dissipation when well cooled and can do 2100W carrier with 4.5KV in class C, plate modulated service full strap. (1500W X 1.4)

T
 
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Steve - K4HX
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« Reply #27 on: February 02, 2018, 10:32:33 AM »

Decades of actual on the air use by many AM ops has proven what JI says to be incorrect. A pair are good for 300 watts and will last a long time. I have a pair that have been in use since early 2000s.

It's best to get or build an amp that runs 3 to 3.5 kV on the plates. The 3-500s put out more power and are more efficient at the higher plate voltage.


Rich, check out these links.  According to Tom, W8JI the maximum to expect from a single 3-500Z is 125 watts carrier.  He goes on to say even that might be too much depending on the amount of cooling you have.  The 3-500Z is really cooling dependent which I didn't know.
http://www.w8ji.com/am_linear_amplifiers.htm

AL-80 history:  It seems the early ones had some problems.
https://www.w8ji.com/Ameritron_al80_history.htm

Al, n7ioh

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n7ioh
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« Reply #28 on: February 02, 2018, 11:18:59 AM »

That reminds me of when I had a 1987 Toyota MR2 non turbo.  The specs said the car had a top speed of 118 MPH.  Going to work one morning before DPS was out yet on a flat stretch of highway I put the peddle to the floor and got the car up to an indicated 127 MPH before letting off the gas.  I don't know how fast it would really top out at maybe 130 MPH.  And yes, my speedo was accurate as I had driven my car through several of those check your speed radar units, where the posted speed was 65 and it was always within 1 MPH.

Doing the math and coming up with what the specs say it should be is not always so.  That is one reason I do a lot of reading and asking people who have used the equipment.  Many things are down rated so they don't have to do a lot of warranty and they last a long time, these are usually the better companies.  The companies that usually over rate their stuff do it to make their stuff look better than it is, charge more money, and do more warranty, they don't usually stay around long.

Well after doing a lot more reading, thanks to the group.  I have decided to go with the AL-1200 with the 3CX1200Z7 tube.  It will take the drive from my Ranger II better than the 3CX1500A7 and be more forgiving should I goof up because of my poor vision.  I really like having a single tube and not having to worry about buying a matched pair and wondering if they are really matched should I ever have to replace tubes.  Yes the 3CX1200Z7 is expensive, I will have to live with that decision should I ever have to replace it.  Thanks for all the input and education.

Al, n7ioh
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Steve - K4HX
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« Reply #29 on: February 04, 2018, 12:04:21 PM »

Have fun with the new amp. Hope to hear you on the air soon!
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