Kris Power Pump Upgrade/ Restoration

[loosecannon]

hi all.

here's the latest on my progress on the kris amp.

almost done with all the wiring, got the bias and input tuning wiring done.

now i just need to add the coax connections, and mount the PC board with the relay.

as always, i have couple of questions.

1. im using a .01uF cap in series with the input, and im wondering what exactly i should be looking for when testing in order to know if im using the right value or not?

2. looking at the schematic i uploaded, RFC2 is coming off of the antenna load cap to ground. am i going to need this?
what is its major function?

ALSO- im a bit concerned about the plate spacing of the antenna load cap that i ordered from RF parts. its the 56-36 in their catalog.
looking at the pic below, are those plates too close together for an amp of this size/ wattage?

here are some pics of the progress:
LC

 

[unit_399]

I haven't been online for a while, and wanted to put in my 2 cents worth too.

I agree with exit13 that a single RFC5 choke is sufficient.

If you are going to add a parasitic supression cap across the secondary of the power transformer, the rule of thumb is that for secondary voltages below 100vac, use .01uf. For voltages over 100 vac, use .001uf.

All tube amps generate parasitic vhf oscillations, and they must be removed from the signal before it reaches the antenna. They are usually removed by installing a resistor/inductor RF choke at the plate output of the tube. But these parasitics vary in frequency depending on the type of tube and the circuit design/ layout being used. Determining the exact vhf oscillation freq of an amp is a long drawn out process, and is a big-time pain in the ass. Parts layout in an amp can have a huge effect on vhf oscillations, and many times a good circuit layout can eliminate the need for a parasitic supressor. Good shielding to prevent any coupling (however small) between input and output circuits outside the tube(s) is essential to eliminate oscillations. If you can find an old ARRL handbook from the 60s, there is a great section on amplifier layout.
.
Looking through my 1965 ARRL handbook, plate voltages of 1000 or less require minimum tank capacitor plate spacing of .015 inch.

The only question I have concerning the schematic, is the connections between the control grids on the tubes. It appears that there is a cap missing in the circuit at the connection of pin 6 of V2 to pin 6 of V3. Not sure though.

Construction techniques look pro. Good luck and 73s.

- 399

 

[loosecannon]

ok, the amp is almost done!

just need to get the tubes tested in order to fire it up fully.

power comes on and voltages look correct.
relay keys when mic button is pressed. (no tubes in amp)

here are the pics of the "finished" product:
LC

 

[loosecannon]

Bringing back an old thread in order to hopefully get some advice on optimizing this tiny beast.

I have been using the amp on and off for a couple of years now, and have noticed that it just won't modulate a full 4x the dead key on AM no matter what you drive it with.

i also think that the tubes should put out a bit more than they are.
(i have tested this amp with three different sets of tubes and the output is always about the same)

right now, on AM with a 3 watt deadkey, i get a 50 watt carrier and about 100-110 watts modulated.
the radio is tuned on the scope for 100% modulation and shows a 3 watt deadkey modulating to 12 watts.

if i decrease the drive to 1 watt, i get a 30 watt carrier, and the amp modulates to 60-65 watts.

If i drive it with a 4 watt carrier, it will key up with a 65 watt deadkey and modulate to 120-130 watts.

on SSB i get a 120 watt PEP output with a 15 watt input.

so, what is it about this particular amp that won't allow it to fully modulate an AM signal so that the peak is 4x the carrier?

also, i would think that with three tubes in parallel, that i should be getting about 180-200 watts PEP out of this amp with the input levels i am giving it.

any ideas on the low output level?

The input to this amp sits at an SWR of about 1.3:1 and did not lower the output of the amp when tuned.

I have posted the schematic i drew up to build this amp, and the only difference from the schematic to the amp as it is now is that there are caps and resistors on the rectifier diodes and the cap that couples the output of the tubes to the pi network.
that cap is now .002uF instead of .001uF.

I have spread and contracted the coil on the pi network and that only serves to move the peak around on the air variable tuning caps.

I have attached the schematic and am hoping someone can see where i could have done better.

thanks for any and all input!
LC

 

[nomadradio]

The only thing I see that makes me wonder would be the 10 ohm resistor in each cathode. Doesn't seem like it should hold you back that much, but it will affect peak power more than carrier.

I don't think they're necessary now that the amplifier has fixed bias on it.

73

 

[loosecannon]

thanks Nomad!

i will try shorting around them temporarily and see if that makes an improvement.

what do you think of my value of .002uF for the cap going to the pi network on the output? (C1 in schematic)

anything to be gained by increasing it to say .0039uF?
I'm not sure if i'm on the edge of letting enough 27mhz RF through with the .002uF value or not.
LC

 

[Onelasttime]

If you can get some 6MJ6's that is a killer upgrade! Why the resistors on each cathode? I could see putting some more resistance on the HV side to bleed the system down and to keep some load on the system and for load sharing. I would consider upgrading the ancient diodes on the diode board/hv board. I switched all of the ceramic caps in mine to silver mica's and I had my plates replated in silver. Anderson Silver plating plates electronic parts to NASA specifications. I also use them for instrument plating. They do copper, nickel, silver and gold plating. I think I had to redo the meter as well because they had some crazy high voltage and no real protection with the meter but I am not 100% sure on that.

 

[Onelasttime]

ok, making some progress!

i answered my own question about the "L1" thing. it turns out that there is a wire about an inch or so long connected from one side of the lamp socket to the other.

its a coil with no coils in it! i would call this some sort of "gimmick" as can be found in other amps, but not really applied the same way.
either way, it alleviates my concerns about the whole amplified RF signal going through the filament of a lamp.

i have installed the new electrolytics in the voltage doubler, and i used 100k 5 watt resistors. open to input on this decision, but i think it will work ok.

i put a new power cord on it, and moved some things around to make room for the circuits im adding (bias and input tuning).
i used a ferrite snap-on bead and wrapped a few turns of the hot and neutral wires through it.
i also added a .01uF 1kv cap from the hot to the neutral wire.

i also started the input tuning section. the idea is to mount a 463 trimmer cap to the side and drill a hole so it can be accessed from outside the amp.

i have also done the bias wiring, and just need a couple of parts before its complete.

more to come...
LCView attachment 15512 View attachment 15512 View attachment 15513 View attachment 15512 View attachment 15513 View attachment 15514 View attachment 15515

Mine had 2X500uf caps where you have 3 100uf caps and they where gigantic paper caps.

 

[loosecannon]

thanks for the reply OLT!

The 10 ohm resistors were an idea from an old ham radio magazine article on building a sweep tube amp and are there to aid in balancing the resting plate currents.

here is a link the the article:
http://www.qro.it/amp/schemi/pdf/72hb176.pdf

as far as the filter caps go, i wonder if you might be misreading the label, if you are indeed referring to a kris power pump. they are 500wv caps in stock form, but are about 30uf each IIRC. you can have a look at the stock caps in the last picture of my first post. click the pic to enlarge and you can see them.

all of the components on this amp have been replaced and the diodes are now 1N5408's with resistors and caps in parallel.

i already have all the tubes im going to ever buy for this amp, including a brand spanking new sleeve of 5 sylvania 6LQ6's.
the 6MJ6's are very tough, but i don't abuse the amp so im not worried about tube life.

LC

 

[Onelasttime]

thanks for the reply OLT!

The 10 ohm resistors were an idea from an old ham radio magazine article on building a sweep tube amp and are there to aid in balancing the resting plate currents.

here is a link the the article:
http://www.qro.it/amp/schemi/pdf/72hb176.pdf

as far as the filter caps go, i wonder if you might be misreading the label, if you are indeed referring to a kris power pump. they are 500wv caps in stock form, but are about 30uf each IIRC. you can have a look at the stock caps in the last picture of my first post. click the pic to enlarge and you can see them.

all of the components on this amp have been replaced and the diodes are now 1N5408's with resistors and caps in parallel.

i already have all the tubes im going to ever buy for this amp, including a brand spanking new sleeve of 5 sylvania 6LQ6's.
the 6MJ6's are very tough, but i don't abuse the amp so im not worried about tube life.

LC

Maybe but I do not think so. Maybe someone replaced them before I got the unit. It all appeared very much stock though to my eye when I got it. I wish I had taken photo's at the time. The caps were so large that were in the unit on the bottom that I was actually amazed that they managed to get the tins on it. So I matched the voltage and capacitance on the side of the cap's. Obviously, the modern ones I used are tiny by comparison. They might not have been paper now that I think about it. The ones on top those next to the diode board where definitely paper.

I lucked out getting the pair of NOS 6MJ6's right place right time right price etc....I did not even know at the time how sought after they are or tough. I got them so cheap that in hindsight it was close to theft. LOL I just paid what they wanted for them and figured I could prob. make them work! LOL Ignorance is bliss! LOL

Thanks for the link I am going to go read it and download it. In terms of your parasitics, I do not know enough to have an educated opinion. There are guys far smarter than me on both sides of the fence that make compelling arguments. The one thing I do think is B.S. is the Nicrome(sp) wire part of it. Outside of heat resistance in high temp applications like the main shaft of a jet turbine engine, some specialty alloys for sliding valve train parts I do not see where there is any magic in Nickle alloys as it relates to electricity and rf.

 

[2315 Robert]

ok, the amp is almost done!

just need to get the tubes tested in order to fire it up fully.

power comes on and voltages look correct.
relay keys when mic button is pressed. (no tubes in amp)

here are the pics of the "finished" product:
LCView attachment 15631 View attachment 15632 View attachment 15633 View attachment 15634 View attachment 15635 View attachment 15636

Radiation sign at full power. Ooohhhh yyeeaaahhh!!

 

[loosecannon]

thanks for the replies guys.

OLT, that is exactly what i was going to ask you, had you not mentioned it in your post.
(how in the heck did they get the bottom cover on it with that big of a cap in it!?) LOL

Robert,
i was hoping someone might mention or ask about that pic!
When i was trying to free up the stuck needle in that meter, i noticed that the decal was peeling off and once i found that it was beyond repair, i peeled it off.

lo and behold, behind the uA decal was a symbol that strikes fear into all that view it!

i have been wondering two things since i uncovered it.
1. where in the heck was Kris buying these things from?

2. has anyone else ever peeled the decal off of the meter of a kris amp and found this?

I like to think that back in the day there was a CBer who stated over the air that his amp was nuclear fueled and could prove it! LOL

LC

 

[2315 Robert]

thanks for the replies guys.

OLT, that is exactly what i was going to ask you, had you not mentioned it in your post.
(how in the heck did they get the bottom cover on it with that big of a cap in it!?) LOL

Robert,
i was hoping someone might mention or ask about that pic!
When i was trying to free up the stuck needle in that meter, i noticed that the decal was peeling off and once i found that it was beyond repair, i peeled it off.

lo and behold, behind the uA decal was a symbol that strikes fear into all that view it!

i have been wondering two things since i uncovered it.
1. where in the heck was Kris buying these things from?

2. has anyone else ever peeled the decal off of the meter of a kris amp and found this?

Obviously the initial fuel rod tubes have been removed(or disguised as tubes that we are used to looking at). Not to worried about you numbers. If you key up and strange cars park outside you may have to go Subterranean.
I like to think that back in the day there was a CBer who stated over the air that his amp was nuclear fueled and could prove it! LOL

LC

 

[Onelasttime]

Well back in the 1980's a lot of Titanium bike frames where made from tubing designed for use in Nuclear Power Plants. That is why they where such large outer diameter and made from titanium. I hit surplus shops up all the time for super strong chains, cables, webbing, bolts etc....Specialty stuff you would never want to pay full price for. 99% of the stuff is surplus from special industries like Mining, Oil Exploration, Aviation, Steel manufacturing, Military ship yards or repair parts from Military Depot level that are obsolete and being released for sale. Those sorts of things have always been true. Look at all the aviation magneto's that made their way into Hot Rods post WWII 1950's as we transitioned from piston engines to jets.

Look at all the Russian Military Surplus tubes, and electronic passive components on the market now!

Today people seldom roll their own parts for something like a linear you buy off the shelf. If you get really lucky you might just find 5000 meters cheap that just need a new scale added to them! LOL

I can tell you this much they did not get them from China or Ebay! LOL I can only imagine what the surplus market had to be like between 1945 and 1980!!!

 

[2315 Robert]

Well back in the 1980's a lot of Titanium bike frames where made from tubing designed for use in Nuclear Power Plants. That is why they where such large outer diameter and made from titanium. I hit surplus shops up all the time for super strong chains, cables, webbing, bolts etc....Specialty stuff you would never want to pay full price for. 99% of the stuff is surplus from special industries like Mining, Oil Exploration, Aviation, Steel manufacturing, Military ship yards or repair parts from Military Depot level that are obsolete and being released for sale. Those sorts of things have always been true. Look at all the aviation magneto's that made their way into Hot Rods post WWII 1950's as we transitioned from piston engines to jets.

Look at all the Russian Military Surplus tubes, and electronic passive components on the market now!

Today people seldom roll their own parts for something like a linear you buy off the shelf. If you get really lucky you might just find 5000 meters cheap that just need a new scale added to them! LOL

I can tell you this much they did not get them from China or Ebay! LOL I can only imagine what the surplus market had to be like between 1945 and 1980!!!

Affirm. Bet you had to know someone. If you did you were set.