All 4-1000 gurus step inside

Discussion in 'Amateur Radio Amplifiers' started by W4EKY, Jan 16, 2017.

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  1. KF4TOH

    KF4TOH Ham Member QRZ Page

    Just a opinion about the mechanical part of your build . the tank circuit / plate choke should be as close to the tube cap as you can!
    the grounds on the caps should be mounted to the same plate as the tube is mounted on ,
    Same with the The tuned input even if its a mono band, hang your tuned input circuit right at the tube pins inside the air box if you can
    . again short and neat leads .. really pays off on the higher bands . the ant relay should be very close to the tube and shielded .
    Sounds like you got the electronics and math . looking forward to updates
    joe
     
  2. W4EKY

    W4EKY Ham Member QRZ Page

    Joe, do you think there is going to be a problem with the lead length between my plate choke, tube and vacuum cap? They will all share same geound, the aluminum rack that the tank circuit is mounted on is bonded to the cabinet as well as the deck that the tube socket is mounted on.
     
  3. KF4TOH

    KF4TOH Ham Member QRZ Page

    Well it could, maybe a little touchy on the higher bands tuning wise . you really should look at all the grounds being on the same plane
    just take a tap and measure point to point "caps to the socket grounds" looking at the picture its a long ways around
    the leads inside the 4-1000 are longer then most, so everything you save will pay off in a stable amp and again same with
    the tuned input and relay switching, .. lets see more pictures ! 73 joe
    ll
     
  4. W4EKY

    W4EKY Ham Member QRZ Page

    The K5LAD and Bill Orr's 4-1000 schematics calls for 3 500mfd blocking caps in the tank circuit. Before I spend the money, i have a sprague 2200mfd 20kv doorknob cap. Will that be a sufficient replacement for the 3 in the schematics? Amplifer will be 10-160m and still undecided on a one hole or two hole amplifier.
     
    AF6LJ likes this.
  5. W4EKY

    W4EKY Ham Member QRZ Page

    One more question. If i build a two hole 4x1 would it be leas then ideal to run two different makes or filament transformers. I have two 117v filament transformers, one is a stancor and other is unknown, but both have identical ratings on primary or sexondary. They will require a variac to get the filament voltage down into specs because of their 117v filament primaries. My variac is a powerstat 116U rated at 7amps. Should it be sufficient to power two filament transformers. The center taps of the filament transformers should be wired in parallel to the changeover relay.. correct?.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    "mfd"??

    I doubt that. Probably mmf (pF) and 1500 pF or 2200 pF should both be fine. The reason a lot of designs use them in parallel isn't to build up higher capacitance (very little is needed), but to increase current handling by sharing the RF current between two or three capacitors. If the single 20kV cap you have can handle all the current, it should work fine; if it can't, it will burn up.:p
     
    N2EY and WA7PRC like this.
  7. W4EKY

    W4EKY Ham Member QRZ Page

    Sorry steve i meant MMF or PF.. here is a pic of the cap its 2200mmf 15kv. How much RF should this can handle? I also have a few of the murata 880 mmf 20kv ceramic caps from mouser
     
  8. KM1H

    KM1H Ham Member QRZ Page

    It had nothing to do with the tube design since GG wasnt used by hams, nor others that Im aware of, for high power until the mid 50's. There were several earlier receiving triodes that used GG, mostly on VHF.

    Any tetrode can be run GG as long it has sufficient grid dissipation which leaves out most external anode tubes such as the 4X150/250 class. Pentodes such as the 813, PL-175, 5-400A, 5-500A, QB5/1750, etc, and many others that do not have the suppressor grid internally connected to the cathode also work well.
    The Russian GU-81M is a popular glass pentode but sockets often cost more than the tube. It also runs very well at only 2000-2500V.

    Most tubes that are run well below their maximum rated HV are inefficient and hard to drive. Ive built many 4X1's running GG with 4200-5000V at full load, when I was doing it as a sideline in the late 60's and into the early 90's, that are quite efficient with 100W drive. Those were the days when BC stations had their own chief engineer and replaced tubes by the time on the filament meter clock and had plenty of life left. Those days are long gone and some stations run until listeners call about weak or distorted signals.

    With grid drive the input was swamped by a resistor to burn off the excessive drive from the typical 100W rig. I learned that method at National Radio in 1963 with the NCL-2000.

    One issue is that most 4x1's are pulls that have been sold several times over and have low emission. Some just crank up the filament voltage to compensate until the tube simply quits. OTOH the 4-400A was used by the military, broadcast and other applications right until today and NIB mil surplus are readily available for much less than a Chinese 3-500G. or an obsolete 4-400Z. In GG it takes about 120W drive vs 100 for the 3-500 for the same output. It is also popular in the SB-220, L4 and 4B and some others when the grids are directly grounded at the socket. In directly grounded amps such as the AL-80 series it is Plug and Play.
    NOTE: Some amps do not have the height clearance for the 4-400A. Often mounting the socket under the the chassis is all that is needed.
    Grounding the metal shell using chimney clips or spring brass at 4 places is recommended for stability when running above 20M.
    I believe Ameritron sells chimney clips for the AL-82.

    Another issue is that most published early circuit examples, including by Eimac, did not use a tuned input circuit which required substantially more drive, plus it was somewhat dirty IMD wise.

    Carl
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    No picture was attached, but I can't tell how much RF current anything can handle just by looking at it.

    If you have the complete manufacturer information (full P/N which includes the series type) usually the detail specifications will indicate this. The ubiquitous Centralab 857 doorknobs, for example, do rate RF current at a few HF frequencies. The 571000-15, for example, is 1000 pF, 15kV and rated 5.1A at 30 MHz, but only 2.1A at 1 MHz. Still, that's usually sufficient for amateur legal-limit power levels.

    https://www.rfparts.com/capacitors/capacitors-cerdoorknob/capacitors-ht57.html
     
    N2EY likes this.
  10. KM1H

    KM1H Ham Member QRZ Page


    What Johnson socket Steve?
    There was the original SK-500 cast aluminum one which was very expensive and had a restricted air flow.
    Later a much cheaper, but still expensive, plastic SK-510 became very popular with hams, it also fits the 3-1000Z and a couple of European tubes such as the QB5/1750 which I use for modulators but with the much cheaper Italian and Chinese sockets which can be modified for decent airflow at more than 1500W with a decent blower.
    For 1500W at intermittent SSB several use a muffin fan below cooling the filament pins and a bigger version blowing on the glass. Whatever works!

    upload_2017-3-10_13-1-24.jpeg
     

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