4-1000 RF deck. What do you guys think?

[ke7trp]

I got this RF deck FREE. 

Thanks to Dmod, I now have a 4-1000 tube and chimney!  I thought maybe this deck could be upgraded and modified.  Maybe its best to just tear it down for parts. 

It appears this is a cathode driven, grounded Grid amplifier.  There is a tuned input with switched inductor and variable cap.

It was probably built in the 60s or 70s I would think.  Half of me says, yes, Upgrade it, Clean it out, Put it in the rack, build a 5000 volt PS and run a ranger or other am transmitter into it. The other half says, Its old, maybe a bit scary and probably should be parted out. It has no metering.  A plate meter would be needed at a minimum.

Here she is in all her Glory:

[ke7trp]

More pictures

[W3GMS]

Clark,

The parts look to be in pretty good shape but the construction practices look a bit marginal in my opinion. 

If you need a HP rig, I would get an new chassis and start over but this time build it as a Class C final amplifier.  If you don't need another big rig, I would help someone else out by making the parts available to them. 

73,
Joe W3GMS 

[ke7trp]

I dont want/need another class C amp.  I was thinking of an amp for a use on AM with a typical ham class transmitter in the 50 to 100 watt range.

C

[W3GMS]

Here again Clark it depends on what your looking to do.  Linear operation is a nice way to enjoy some of the lower power rigs in all their mystique by driving an amp.  Normally you would not need any where need 50 to 100W of drive to the 4-1000 in linear service for the legal output power of 375 watts 100% modulated.  I drive a pair of 3-500's at about 18 to 20W for legal limit output.  Yes, you can use various techniques to reduce the drive of the exciter.  It just depends on what you what to do.  I would still rebuild the amp since the construction practice looks very marginal.

I saw your T-3 up for sale, so I guess you still have the GK rig.     

Joe, GMS

[ke7trp]

The 4-1000 needs alot of drive in Grounded Grid unless the voltage is up to 6500 to 7000.  At 5000 volts.  It takes some serious drive to get her going.  Maybe less with the tuned input. 

Yes. The T368C is for sale. I finally got the rig working 100% thanks to the help of the guys here.  The last issue I had was a bad 0a2 in the PTO supply.  That tube was flickering and causing a very nasty hum/buzz on the signal.  It was covered up with a IERC tube shield so I never noticed it.  That tube checks perfect on the Tv7. However, When I replaced it with an RCA 0a2, The color is solid, the voltage is exactly 150 volts and the transmitter is spotless clean.  I even used a small DC supply to DC the filiments to the Exciter.  The rig now runs better then new.  I am just ready to move on and put another rig in its place. My ham shack is tiny.  I have so many rigs to install.  Its also time to put a roof on the house which is costing me a fortune.

C

[KA2DZT]

Clark,

The front panel looks good.  I don't like the placement of the tank coils.  The axis of the coils should be parallel with the shafts of the tuning caps.  It looks to be a grounded grid amp as I see a B+W filament choke.  I would try to rework what's there.  Maybe replace the tank coils.

Fred

[W3GMS]

Here is a very good reference design for a 4-1000 GG Amp.  The design is sound and the layout is good.

You will need to scroll through the document since it discusses several different tube amplifiers. 

Joe, GMS

[K3YA]

I've certainly seen worse construction.  A lot of good parts there although the placement of some, like the filament choke, leave something to be desired.  Also mounting the tube where you  can monitor the plate color would have been nice.

I have both a GG and grid driven 4X1 in operation here.  The GG one runs at 5.5KV and I drive it with a TS930, about 135 watts. That gives me 2.5+ out with 900mA plate current (dummy load, testing etc).  A 5 kv supply would be fine.  You could probably even overdrive it with a Ranger.

You would need a plate and grid meter.  I find that monitoring grid current is very helpful while tuning.  There's plenty of room on the front panel two (or more) meters.

I like the tidy it up an run it idea.

[KM1H]

The 4-1000 needs alot of drive in Grounded Grid unless the voltage is up to 6500 to 7000.  At 5000 volts.  It takes some serious drive to get her going.  Maybe less with the tuned input.

Far from it unless its soft.

At 4000V 100W will get 1500W to 15M, a bit less on 10. A typical 120-130W tube exciter such as Drake, Kenwood hybrids, etc, will get it to 1800W to 15M and 1500 on 10.

This is with a well matched tuned input. Now if all you use is a .01 cap then add another 1000V.

For AM you need 1/4 the drive for roughly the same PEP output so a Ranger would be fine or one of the carrier control rigs or even an AF-67

That amp looks like he did a bit of shopping at Barking Willy and tore apart one of their output tanks and just used the coils. Maybe I sold it all to him back during my Radiokit days of mail order while getting my edumencation to be an injuneer.

The construction is "acceptable" for the bands used and Ive seen HB from Top of The Honor Roll DXers look worse than that. I have one from a very famous (SK) MA DXer that I wouldnt even allow into the house; its still out in one of the trailers after 23 years!

That 800 choke wont make it to 160 very well, get an Ameritron if you want a good one.

The less HV you use the easier it will be as well as cheaper. Get too carried away and you will be needing vacuum variables and relays and a huge mutha bandswitch all for the same power an 8877 will give you at 3KV.

That amp looks like it was likely run pretty legal or a bit less.

Carl

[ke7trp]

This is what I was thinking:

1. Change the plate choke to the modern RF parts/ameritron choke.
2.  Redo the wiring under the deck and move/replace the BW fil choke.
3. Add a 120 volt socket so the deck would power up seperate from the PS
4.  Add a plate current meter.
5  Add a Grid meter.
6.  Gather parts for a 5000 to 6000 volt supply with tune for low voltage tuning.
7. Let her rip.

What do you guys think of the other deck?  Kinda makes the free one look like a bunch of parts huh?

[ke7trp]

more pics

[KM1H]

Id loose that old aluminum slug of a socket and use the plastic one and you can just about cut the blower CFM in half.

When those were the only thing available we used to cut out every other tab in the tube base so a blower could be used that didnt sound like a turboprop. Even then a lot of CFM was still needed when pushing the RF.

Carl

[K3YA]

That's nice.  I really like the window.  And it's grid driven...needs a modulator.  

I'm personally not a fan of roller inductors on big amps.  Also like the plastic socket with a pressurized chassis.  Less turns for the air to negotiate.

[KA2DZT]

Clark,

That amp really looks good, nice construction.  Did you build it??

Fred

[ke7trp]

No. Its class C.  I could change it for Grid driven service.  I dont need another big transmitter here. I would really like an amp that will take OLD buzzards with a classic AM TX into it.

C

[Opcom]

that plate tuning cap there looks like it's for the low side of the plate voltage range. Do you know what voltage was being run on it?
I'd strip the wire out and redo it, it is very helter-skelter. move the fil. choke closer to the tube.

[KM1H]

move the fil. choke closer to the tube.

NOPE, at least not as a knee jerk reaction.

Measure the voltage at the socket in standby and under full load. Shoot for exactly 7.5V in standby and no more than 5% low under full power. Result is long life. You can always use a Variac to tweak as the tube ages and Ive seen some run the 4X1 up to 8.5V as the last gasp.

The way I do it with expensive or hard to find tubes is to start with the tube manual bogey voltage and then, at full power, reduce the filament V until the output just starts to drop. Then increase a tenth of a volt and use it. Test this on a regular PM basis or better still include a meter if your line voltage is all over the place.

Carl

[ke7trp]

Clearly the builder of the old deck used what was on hand and probably ran it at low voltages.  I am not sure about this project. You really need to get alot of voltage to make these tubes run. 

C

[k4kyv]

Some nice air variables, but spacing is a little on the low side for 4 or 5 kv on the plate if it were plate modulated.  Maybe OK for linear service, since the peak rf voltage wouldn't be much over 4 kv or so. Quality of the parts inside looks better than the quality of construction.

Clean up the layout a  little, add meters, and run it as a linear or grid modulated amp, at about 3500v/350 MA to the plate (not counting screen current). That would allow a little better than 1 kw DC input to the plate and about 350-400 watts carrier out @ 100% modulation, and the tube would run conservatively.

[Opcom]

move the fil. choke closer to the tube.

NOPE, at least not as a knee jerk reaction.

Carl

I don't experience that kind of reaction and so the concept is really foreign to me. I don't know how such a vehement rebuttal fits here except that the written word was not understood and the unwritten words were misread instead 8-).

To be clear the purpose of moving the choke is to shorten the length of wire carrying RF voltages. It is best practice to keep RF leads short so they radiate less to other things.

[KM1H]

Vehement? You must be one of those overly sensitive types and were so affected you had to remove, reword and repost a 4 day old reply since I didnt answer as I didnt feel my reply would be productive.

So now you got my attention...you happy?

While I would agree with relocating the filament choke if the amp went to 10M its not going to bother anything as built. Maybe with a SS exciter and an untuned input.

Even on 10M the drive impedance of a GG 4X1 is so low and any reactance is easily tuned out by a tube exciter that it should have minimal effect and especially any reradiation.

Carl

[DMOD]

Glad to see the chimney made it intact.

Are you going to use the chimney to protect and cool the BL, or use it for the 4-1000  

I too would use larger spaced cap plates for PI-L and run it triode in GG config.

I know a tuned input may require a bit more design and a few more components, but the Eimac paper is a good starting point.

This should be an awesome linear.



Phil - AC0OB

[Opcom]

Vehement? You must be one of those overly sensitive types and were so affected you had to remove, reword and repost a 4 day old reply since I didnt answer as I didnt feel my reply would be productive.

So now you got my attention...you happy?

While I would agree with relocating the filament choke if the amp went to 10M its not going to bother anything as built. Maybe with a SS exciter and an untuned input.

Even on 10M the drive impedance of a GG 4X1 is so low and any reactance is easily tuned out by a tube exciter that it should have minimal effect and especially any reradiation.

Carl

Carl, I apologize that you are upset. I didn't remove the original post. If you had paid attention before, you might have noticed that I carelessly put a beer picture in it which had nothing to do with the interesting amplifier, which is what we are interested in discussing.

The new text was posted 4 days later because I have work to do, so I did not get around to this particular thing promptly, for which I sincerely apologize, but even belatedly I felt that my opinion about the choke position was worth mentioning and of course the 'reaction' assumption in the reply required correction. That's it, no more and no less.

It should not need to be explained that the words were indeed different because I didn't remember the words previously used to explain what I believe was misunderstood, and why I prefer the choke moved. Vehement is a polite way to suggest that using all caps in the first line after a quote is shouting at the one who was quoted. I apologize for being indirect but I did not wish to be rude.

Please, do not presume to make assumptions about my actions, reactions, or reasoning.

There will be no unpleasantness from me over where I prefer the choke or anything else but I will freely present my opinions as objectively as possible and they are based on some experience of one kind or another or I would not put them forth lest someone be misled.

In my own work I must put other circuits close to low frequency RF leads from time to time, so I prefer to keep all of them (even less potentially troublesome ones such as this filament circuit having only perhaps 100 peak volts) as short as the construction will allow, in this case quite short. I do not believe this requires further explanation.

I don't wish to lower the situation to a rude or unpleasant exchange over an opinion so now that this is cleared up I would kindly prefer not to discuss anything else other than the amplifier.

[W7TFO]

Hey, Pat, but what about that dorky hat you always wear ?

I have one just like it !

73DG