Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Ameritron's 3CX1200Z7 or 3CX1500A7 for my Johnson Viking Ranger II




 
The AM Forum
October 22, 2018, 10:01:38 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2   Go Down
  Print  
Author Topic: Ameritron's 3CX1200Z7 or 3CX1500A7 for my Johnson Viking Ranger II  (Read 3059 times)
0 Members and 2 Guests are viewing this topic.
n7ioh
Member

Offline Offline

Posts: 33


« on: January 29, 2018, 06:11:34 PM »

First let me say I don't know much about Amps.  My only amp was the Heathkit SB200 that I built in the early 80's and used very little.  In looking at the two Ameritron amps for use with my Ranger II, I am leaning towards the AL-1200 with the 3CX1200Z7.  My reason is mostly the fact the 3CX1200Z7 has a grid displacement of 50 watts vs the 3CX1500A7's 25 watts.  With the Ranger II I will be using it only on AM, 75 meters and up.  I do plan on using the amp with my other radios on SSB and maybe AM, but for this discussion I am only concerned with the amp being used with the Ranger II.  I will be running a dedicated 240 VAC line for the amp.  So pros and cons, discussion, let me hear from you. 

Al, n7ioh 
Logged
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 6931



WWW
« Reply #1 on: January 29, 2018, 07:19:46 PM »

That 3CX1200Z7 tube is super expensive >$1000 and going up. I wouldn't go there, but your mileage may vary.



Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
n7ioh
Member

Offline Offline

Posts: 33


« Reply #2 on: January 29, 2018, 07:49:57 PM »

Yes, they are both expensive.  I checked yesterday and from Ameritron the 3CX1200Z7 was $1,995 and the 3CX1500A7 was $2,095.  Now that's not real world pricing and the 3CX1500A7's are readily available as pulls where the 3CX1200Z7 is not to my knowledge.  My view is at 68 years of age ether tube should last longer than I will.  I did also think about buying the AL-1500NT which is without the tube and just buy a 3CX1500A7 pull and go with that.  I may still go that way.  The 3CX1200Z7 requires more drive for full output than the 3CX1500A7, ~100 watts vs ~65 watts.  That is also one of my considerations/concerns.  The Ranger II does not have a lot of watts with only a single 6146A. 

Al, n7ioh
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 1877


Making AM GREAT Again!


« Reply #3 on: January 29, 2018, 10:45:44 PM »

The Z7, IIRC, has a grid ring in it, for superior shielding.

It is NOT  a broadcash tube, so I wouldn't expect ChiCom to be producing it.

It is NOT considered one of the 88xx series of 'linear' tubes.

The one specimen I played with reminded me of Howell's 3cx1600 of years ago.  30 amp 5 volt filament, 3-500Z base and 1.6kw plate dissipation.

The original 3cx1200A7 was a drive pig.  Otherwise, pretty indestructible.   

The 1200 tubes are thoriated tungsten. The 88 series are oxide cathode.  Thoriated tungsten = can take mistuning better, almost to zero warm up time, low(er) gain.  Oxide coated usually have smaller grids, closer spaced, a real cathode, and have warm up time, some into the multi minute area.  The oxide tubes are usually a LOT higher in the gain department.  Like 10db vs 17 in some cases, for triode.

The 3 hole Amp Supply is a worthy contender for long winded am.  It's almost 500 to retube with Chinese tubes, but isn't made any longer.

--Shane
KD6VXI
Logged
WD8BIL
Contributing
Member
*
Offline Offline

Posts: 4223


« Reply #4 on: January 30, 2018, 12:38:26 PM »

Go with the 1200! It's extremely rugged. That would be my choice....hands down!
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7587


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


« Reply #5 on: January 30, 2018, 03:51:10 PM »

This is more of a DIY project, but here's how I would do it...

Find an amplifier with a blown 8877 or 1200. Buy it cheap.  

Then locate a used YC-156 or YC-179 (3CX-5000)  MRI  pull for $300 or the going used price. (5KW plate dissipation tube)  Rewire with a new 15VAC fil transformer. No socket required - bolt the grid ring to the chassis directly. (GG) This tube has similar gain characteristics to the 8877 with an amplification factor of 200.  It's like 3 1/2   8877s on steroids.

A string of forward-biased diodes in the cathode choke lead will give you solid, fixed bias to obtain the proper idle.

If you run it harder than the original tube, you will have to tweak the plate tank coil for the lower impedance, but it will give you "Borg alien technology" power and limited only by the power supply current capability and the plate tank power capability.

This tube is the cleanest in the linear service world and uses very little filament power because it is indirectly heated.

Since it will be run at reduced power levels it will require less air than normal, will be very quiet and last a lifetime. Running it at 1/4 power will make it even cleaner than -40 dB 3rd IMD.  No reason to spend $2K for an overpriced 8877 tube when this option exists.

http://www.yc156.gs35b.com/

Tom, K1JJ


* YC156A.jpg (51.44 KB, 836x1306 - viewed 122 times.)
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
WD5JKO
Member

Offline Offline

Posts: 1712


WD5JKO


« Reply #6 on: January 30, 2018, 06:47:11 PM »

The Ranger II does not have a lot of watts with only a single 6146A.  

  Realize that that at 100% modulation, that Ranger will provide somewhere between 150 to 200 watts PEP for a 37 to 50 watt carrier. Could be more with modulator tweaks. An amp with 10db gain will then provide 1500w to 2000w PEP. More gain than that, and you either need an attenuator, or move into class BC bias scheme (lowers gain, and boosts efficiency, but not for SSB).

   Those 8877 pulls can be a mixed thing. I have lost several of them, The problem is with amplifiers that ground one side of the filament, and use a high value cathode bias resistor to cut off the tube when in standby. A momentary heater-cathode short, and the tube conducts when the T/R relay is not energized. There you are sitting in the hamshack with linear amplifier turned on, not keyed. Next thing, SNAP SNAP, and the fuse blows. The 8877 filament is now open*. A wicked parasitic just occurred. This happened to me TWICE!! Then I buy a 3rd tube, the pulse version. After about a year of normal operation, it too shorted heater to cathode, pulling 200ma cathode current when in idle mode. Fortunately it did not self destruct. Later, I floated the filament and drove both filament and cathode. That works fine, even though I have a dead short heater to cathode.

   If you choose and 8877, better look for them in quantity if you see a good deal!

* I learned that the filament could be reattached temporarily. I had a test socket with a 100,000uf 15v cap across the filament. I would charge the cap to 12v, with tube in the socket. Then with a rubber mallet I learned where to hit the tube (side blow). When successful, the filament spot welded itself back together. Then put the tube in the amp, and bring up the filament with a variac....worked like a hose!! Next time I needed the AMP, I had to repeat the process. PITA!

Jim
Wd5JKO

    
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #7 on: January 30, 2018, 06:56:59 PM »

So Jim, would you suggest the 3CX1200Z7 AL-1200 Ameritron over the 3CX1500A7 AL-1500 based on it being more durable (50 watts grid dissipation) and requiring more drive?

Al, n7ioh
Logged
WD5JKO
Member

Offline Offline

Posts: 1712


WD5JKO


« Reply #8 on: January 30, 2018, 07:07:56 PM »

So Jim, would you suggest the 3CX1200Z7 AL-1200 Ameritron over the 3CX1500A7 AL-1500 based on it being more durable (50 watts grid dissipation) and requiring more drive?

Al, n7ioh

  Al, I don't know. Tom K1JJ had a pretty good idea too. If it were me with my junkbox, I might pick three or four 304TL's in G-G in the hope for about 6DB of gain from a 100 watt carrier 400w PEP exciter.

   You could also look for a Johnson Desk KW. These are designed to use a Ranger as the RF and audio exciter. Running the amplifier class C and modulator class B would be ideal. The Desk KW also can run grid driven class AB for SSB, or low level AM linear usage.



Jim
Wd5JKO
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #9 on: January 30, 2018, 07:17:37 PM »

I am not physically able to solder or do anything that requires depth perception.  I have Macular Degeneration in my right eye and I am unable to determine where the soldering iron tip is.  I also miss a lot of detail when looking or working on things.  If my eyes were better I might try to adapt an amp or simply build an amp with a seperate power supply.  This is one reason for wanting something new so I won't have to work on it. 

Al, n7ioh
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 1877


Making AM GREAT Again!


« Reply #10 on: January 30, 2018, 09:28:44 PM »

Jim,

In the late 80s, I was responsible for a 3 x 8877 amp.

That thing shorted what seemed like monthly!

Ted at Henry and Reid Brandon got so tired of waranteeing tubes that the last trip up we where 'presented' with 3 x 1200A7s, so let's and a new fil xformer.

NEVER had a problem again, though the drive requirement nearly tripled.

Fast forward almost 30 years and we start hearing about the bad date code 8877s, etc.

--Shane
KD6VXI
Logged
WD5JKO
Member

Offline Offline

Posts: 1712


WD5JKO


« Reply #11 on: January 31, 2018, 07:37:55 AM »


  Al,

    OK on the eye issues. I am about to turn 62, and I really need light and magnification to do detailed work. I struggle, but I still can do surface mount repair. As to depth perception, I was once an avid ping pong player. One of my more formidable partners had one glass eye! Look into chelation, http://www.healingtheeye.com/Articles/Chelation-new.html

     Based upon your needs, and limitations, a brand new store bought AMP with the 3CX1200 might be the better choice. Then again, since you are willing to spend some significant coin, keep an "eye" out for a restored EFJ Desk Kilowatt amplifier. The Ranger was designed to drive the Desk KW. When on high tap, they will make ~ 750 watts carrier which will modulate to about 3KW PEP. That might sound like a lot, but compared to a 24 pill class E rig, this is low power Shocked

Jim
Wd5JKO
Logged
w1vtp
Member

Offline Offline

Posts: 2610



« Reply #12 on: January 31, 2018, 05:00:27 PM »

If you're buying a new amplifier, why not get one with a pair of 3-500z's?  The Ameritron chassis are the same on all these amplifiers.  All Ameritron does is install a different sub-chassis that can be pressurized.  The replacement cost is way less than the aforementioned tubes.  The grid dissipation is 20 watts per tube X 2 = 40 watts.

My Al-82 will output to 2000 watts without flattopping on a trap.. scope pattern.  I don't run it that way - I keep it around 1200 watts PEP and that's plenty

I still think you will have to build an attenuator for use between the Ranger and any gg amplifier.

Huh? Al
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #13 on: January 31, 2018, 06:10:23 PM »

Al, I like the idea of the two 3-500ZG tubes.  If it used a fan and not a noisy blower I would be more tempted.  The single tube one from Ameritron uses a fan and so do the two tube SB-220's.  If I have to put up with the noise, I might as well go big.

Al, n7ioh
Logged
w1vtp
Member

Offline Offline

Posts: 2610



« Reply #14 on: January 31, 2018, 06:37:41 PM »

Al, I like the idea of the two 3-500ZG tubes.  If it used a fan and not a noisy blower I would be more tempted.  The single tube one from Ameritron uses a fan and so do the two tube SB-220's.  If I have to put up with the noise, I might as well go big.

Al, n7ioh

'Sup to you.  I wasn't aware that the other tubes in the Ameritron AL-### used quieter blowers.  The blower system that, for example, the SB220 uses is inadequate for full power service for the 3-500z. Air has to be directed from the bottom up - in a chimney and out the top to properly cool the 3-500z especially to keep the tube filaments from de-soldering. Yeah, I don't like the blower noise in the AL-82 but I've separated myself from it and the noise isn't such a bother.  Heck, look at what Ken W2dtc1 does.  That's drastic but it works.

GL Al
_____________________
1 http://w2dtc.com/
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 1877


Making AM GREAT Again!


« Reply #15 on: January 31, 2018, 08:25:21 PM »

The biggest problem with the sb220 is the 600 Watt plate transformer.

Use it at full power am and the transformer cooks.  Usually before you lose the solder.  Some have resorted to a separate muffin fan cooling the transformers.

The caveat here is:  properly lube and clean the fan yearly.

The Amp Supply I mentioned earlier has 3 x 3-500Z tubes.  And a plate transformer to match.  Finding one........

Al, the one hole al80 uses a fan, like the sb220.  Not a blower.  So do the lesser amps, but that's why the al80 is so much quieter.

--Shane
KD6VXI
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #16 on: January 31, 2018, 09:13:39 PM »

Al, I like the idea of the two 3-500ZG tubes.  If it used a fan and not a noisy blower I would be more tempted.  The single tube one from Ameritron uses a fan and so do the two tube SB-220's.  If I have to put up with the noise, I might as well go big.

Al, n7ioh

Al, the one hole al80 uses a fan, like the sb220.  Not a blower.  So do the lesser amps, but that's why the al80 is so much quieter.
--Shane
KD6VXI


I know the AL-80 & the SB-220 uses a fan, that's what I said.  My point is if the AL-82 used a fan I would consider it.  Again, if I have to put up with the blower noise of the AL-82 I might as well go with the higher power amps (AL-1200 or AL-1500) which also have a blower.  It just seems to me if many other amp builders over the years can build an amp using two 3-500Z tubes without a blower than I would think Ameritron could do the same providing a cooling FAN for the pins and one for the tubes, and yes for the transformers too if needed.  Talk to most owners of amps with blowers and one common complaint is the noise.  The AL-82 is a great amp and the reviews clearly show that.  So why can't they remove the blower, reconfigure the case for cooling by fans.  Is it because they are using the same chassis for the AL-1500, AL-1200, and the AL-82 and it cheaper and faster to use one chassis for multiple amps rather than build the AL-82 from the ground up with FAN cooling?  I know the 3CX tubes require forced cooling and the blower is about the only way to provide the CFM needed, but a pair of 3-500Z has worked in the past with fans only.  Just my thought.

Al, n7ioh
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 1877


Making AM GREAT Again!


« Reply #17 on: January 31, 2018, 10:49:11 PM »

My comment about the al80 having a fan was directed at / towards Al.  He had questioned whether they used different blowers / quieter blowers in the different chassis.

As to your question about the legal limit Ameritron amps:
Yes, they use a standard main chassis with a sub chassis for the tube(s).

The AL82, AL 1200 and AL 1500, except for the tube sub chassis, are basically identical.

--Shane
KD6VXI
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #18 on: February 01, 2018, 01:22:52 AM »

Sorry Shane, I'm Al also. 

Al, n7ioh
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7587


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


« Reply #19 on: February 01, 2018, 01:32:05 AM »

I've had poor luck with 3-500Z amps that use just fans. Two reasons: The filament pins still dripped out solder despite a bottom fan cuz the air flow up thru the socket was poor   - and the top fan cooled just one side of the glass and left the other side hot.

The best way to cool is with a set of glass chimneys and a blower pushing forced air in from the bottom.  I have two  3-500Zs amps with chimneys. One used just a fan before I converted it. I made a small pressurized sub-chassis box for the tubes with a Variac-controlled blower mounted directly to the back of the sub-chassis inside the amp.  What a difference in plate color and no more solder drip. Full AM operation demands it if the tube seals are gonna last. Yes, you can really see the difference in a darker plate color since the heat is no longer hanging around.  Radiant AND convection cooling is important for glass tubes with fragile seals. IE, seals are the weak point of most tubes and usually fail from heat or mechanical stress.

T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
KF7WWW
Member

Offline Offline

Posts: 64


« Reply #20 on: February 01, 2018, 09:10:56 AM »

Noise = Cooling... No free lunch.. Often the more air flow, more noise follows... Id rather deal with a little noise and have the tube/ tubes last. But that’s just me.
In all reality. Any amplifier with the 3-500z tube is ideal for the situation at hand..   
Logged
W1ITT
Member

Offline Offline

Posts: 253


« Reply #21 on: February 01, 2018, 10:04:47 AM »

All cooling air is not the same.  The usual practice is to use a fan or blower spinning at 3600 rpm.  Dayton, and others, make blowers that run at 1800 rpm, and use different impeller designs that don't thrash the air as much, and end up making much less noise for the same amount of air at a given back pressure.  Any noise represents energy that was put into the operation and wasted.  Generally, the noise created by a lower rpm setup will have a different noise spectrum that is easier on the ears and the brain, making it more comfortable to be around for longer periods.  Those little phonograph motor whizzers in the Heath amplifiers sound tinny.
My GS35B project uses a Dayton blower cranking at 1800 rpm, and it has that nice sound that bespeaks authority and strap.  Get rid of those whizzers and go for a slow roller.
Logged
WD4DMZ
Member

Offline Offline

Posts: 97


« Reply #22 on: February 01, 2018, 11:16:34 AM »

My only amp is an original AL80 purchased in 1983 and still using the original 3-500Z. Early on I noticed how hot the chassis and cabinet got so I called Ameritron and asked about the airflow. They said it would be OK to remove the resistor in the fan circuit to speed up the fan.

What I did was put in a front mounted toggle switch to shunt out the resistor when I wanted more air flow. With the resistor out of the circuit the fan really moves the air and is noisy. So, when just idling I leave the resistor in the line but when pushing the amp I switch it out.

When on AM I drive it with an old TS930s and usually keep the carrier around 150 watts. That is a PEP of about 600 watts so the tube is not working hard. About the max I run it at is 200 watts carrier so the PEP is around 800 watts. I could probably run 250 watts carrier but there is not much perceived difference to a listener.

So, with more air and not pushing the tube I now have a 35 year old tube still working great.

Question to anyone knowing more about the tube, do you think 250 watts of carrier is ok?

Also, do the new 3-500G tubes have exactly the same physical size as the old Z? There is very little clearance from the plate cap to the cabinet and even an 1/8" increase in the vertical dimension could cause an arcing problem. I asked Ameritron about the minimal clearance when talking about the resistor and they sent me a set of tube socket spacers that were about an 1/8" shorter then the original ones. I did install them just to ease my mind.

Thanks, Rich
Logged
n7ioh
Member

Offline Offline

Posts: 33


« Reply #23 on: February 01, 2018, 03:53:45 PM »

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
Logged
WD4DMZ
Member

Offline Offline

Posts: 97


« Reply #24 on: February 01, 2018, 07:43:34 PM »

Thanks for the great info Al. My SN is 286 so it appears I am on the edge of rebuilt. Fortunately I caught the plate cap clearance issue on my own and Ameritron supplied the parts. There was another mod they supplied parts for but I forget what it was for as that was almost 35 years ago. Whatever the case, mine has performed well for a long time and the only recent maintenance was cleaning the T/R relay contacts.

Regarding the 125 watt carrier I am sure glad I never pushed much beyond that point. I will cap the carrier at 125 watts now. If I purchase a new amp someday it will likely be the AL80B because of tube availability and cost.

Regards, Rich
Logged
Pages: [1] 2   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.05 seconds with 18 queries.