The AM Forum

  SANTA IS GIVING ME A HENERY 2 KD ORINGINAL WITH NEW MATCHED 3-500zees.THE AMP WILL BE DRIVEN WITH A RANGER WITH FULL (TIM TRON ) AUDIO MODS.   OUTPUT## ??? ANY ADVICE  ??? THIS IS MY FIRST AMP 8)

Yes, use the Timtron low power mod to get the right amount of drive. Swamping a Ranger's output throws dynamic headroom of the modulator out the window.

Tune the amp for max smoke with higher drive power then reduce drive but leave the tuning alone.

http://amfone.net/Amforum/index.php?topic=22453.0


The Apeman is right - tune any LINEAR amp up for maximum smoke to have it optimized for your highest audio peaks.

To keep from "smoking" the amp when tuning it at maximum carrier, build up "The Belcher." It's a simple 555 chip circuit. I use this quite often to produce a ~15% duty cycle signal that will let you tune the amp to maximum peak power but keep the AVERAGE power down low so it does not stress the components. Plug it right into you rig's audio and use it on ssb for tuning.

You will see peak power on the scope or peak reading wattmeter and average power on an average reading wattmeter. The linear amp will tune as if it were receiving a full, dead carrier, which is a good thang.

The pulse sounds like a raspy chirp on the air on ssb. Tune it up in ssb and it will be ready for peak power AM operation once you reduce the carrier down to about 1/5 from the maximum peaks you see.

You can also use the Belcher on AM to tune the linear amp for peak power, though the constant AM carrier will add to the stress. SSB is the best choice for tuning if you have it available.

Good luck with the new FB Henry amp!

73,
Tom, K1JJ

Check the amp to see if there has been a "bias" mod put in.
Early 2K-x amps did not have anything to lower the quiescent bias.
Later ones had something that looks like a transistor mounted on the rear panel, looking at the rear that would be the left... it is not a transistor it is a high power Zener.

IF you do not have the zener factory installed and there is no zener in there, it is a good idea to put one in, otherwise the quiescent current is a bit high. I think they used 10 volts, but I'd have to check. It goes in the cathode...

The other thing you can do is to visually look at the plates when the amp is keyed, zero carrier. If they are glowing too bright - like orange or white, you definitely need to increase the negative bias. The plate meter will tell you the quiescent current.

Another problem with them is fried plate iron due to shorted or very leaky PS caps... I'd bring the amp up very slowly on a variac unless it is known to have been run somewhat recently... to bring it up slowly, you'll have to do some bypassing in the PS circuit, since it uses a relay to key the B+ iirc ...

Also check the resistor that is used to measure the plate current - it sits at the bottom of the Plate supply...they often go bad. They also serve as a sort of fuse for the supply. You might want to install a simple plate fuse via a pair of standoffs and a bit of thin wire... you can find that in one of the handbooks or online, maybe even discussed here.

Also definitely check the B+ "bleeder" resistors - they are actually swamping resistors, get very hot and often have cracked and died... then the B+ will swing up above 3kv... not good...

                    _-_-bear

Yep. That old amp needs some work for sure. We usualy gut them out, sell the iron and choke in the PS off.  Then trash the RF deck.

Expect 150 to 200 watts AM out of that at a maximum.  You can use a Coax T connector and a dummy load sitting down the floor to reduce power. The ranger does not care much about what load its Driving.  You can also build the power reducer. Its in the Johnson Thunderbolt manual.

The last option and probably the best on is to put in adjustable Screen voltage on the ranger.  w3am has a schematic on his site with this. Its just a couple resistors and a 4 watt pot. This way, you can lower the carrier power of the ranger up and down a bit. 

To me, The ranger can run right into that amp though. Just load it up at 30 to 40 watts output, Back off the drive a bit, then overcouple the load on the amp a bit to get the carrier down to 200 or so. THen it should work as is.

C

Yeah, mine required lots of work too. I eventually gutted the HV PS and built my own. I got rid of that fan and mounted a squirrel cage with Variac control on the back. MUCH better air flow. Also got rid of all that JS stuff hanging off the grids (NFB parts) and used copper flashing to strap all the grids directly to chassis ground. More stable.

I thought the final tank and input tuning were OK as is and stayed with it.

Finally, I reduced the HV (Variac) down to about 1500V and loaded it VERY heavily. (No cathode bias) It produces the cleanest 250 watt pep driver you will ever find out there, maybe near -45db 3rd order IMD.  If I Variac it up to 3KV and load it normally, it's a nice 1500++ watt amp.  I love my Henry now with these mods. Nice looking front panel and solid ass.  Just like Pamela Anderson used to look.

T

Think about what is happening to the modulator load when the screen voltage is reduced or the Ranger is lightly loaded. Why drive a pair of big bottles with crap? Great way to make friends on either side of the signal.

Just a note - the stock Henry 2K series that I am familiar with all have the filament windings on the HV iron, so variac-ing the AC is not an option, unless one installs an external bit of filament iron...

Trp - let me know next time you have kilt a Henry... I was looking for plate iron for the past many years for a 2K-D... well fried it tis.

                  _-_-bear

Yes. You need to load the ranger up and cant run it to low or the mod match goes out the window. However, You can load it down 10 watts or so with out issue. They show how to do this in the manual.

Many, many people have run rangers into 3-400s or 3-500s with no swamp box. Its nothing new.



C

How can the rig make a quarter Po using factory B+ without wacking out the load presented to the modulator?
I wouldn't use an attenuator either unless I lost my ability to solder and read a schematic.
The people who wrote the manual could have been the same folks who designed the Ranger to be able to fry an egg on STBY.

1/4 power output?   40 watts is 1/4 huh?   Show me a ranger that does 160 AM.   :o :o :o :o

While I'm one of the "grid grounders" because I believe it increases stability, Billy Orr was one of the guys that DID promote lifting the grids above AC ground to provide a bit of feedback, as well as to increase drive requirements for the exciter / IPA used.

In the Orr Handbook I have, in the dedicated 160 2X3-500Z amp, he discusses how to change the NFB caps to achieve this.  Unfortunately, I've loaned it to a local friend.....  Always when ya need it.

Keep in mind, I and others believe this INCREASES stability of the amplifier.  HOWEVER, you may be able to get a value cap that allows you to drive the amplifier correctly AND not blow anything in the Junkston.

I've never tried it...  I ground the grids in my GROUNDED GRID amplifiers.  BUT, I believe your Henry already has the chokes in place necessary....  You'd just need to play with the amount of C in parallel to get the amount of gain reduction necessary.  As a side benefit, this may help lower IMD, as it IS feedback.

To give ya an idea, I generally see anywhere from 20-30 percent REDUCTION in drive needed AFTER ripping the LC network OUT and directly grounding the grids.


--Shane
KD6VXI

This one and hundreds of other Ranger "Ones."   It's right on the bandswitch. ;D

LOL.   You got me there steve.

C