ad: ProAudio-1


Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Jan 11, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: Subscribe
ad: L-MFJ
ad: FBNews-1
ad: Left-2
  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    There needn't be any kind of delay for HV. I place full B+ on 4CX250Bs (and similar tubes) all the time, even if they're turned off (no heater). Never had any kind of failure. The tubes in my old P-P 2m amp are from 1979 and work the same today as they did back then.

    You just can't "drive" the amp until they're warmed up. The only important delay is the one that "keys" the amplifier into "operate" from "standby" and allows RF to drive it.

    Simple is usually best.
  2. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    OK, based on Steve's sound and Proven advice; it is time for a REDESIGN of the Redesign!!
    I will let the HV come on at AC Power (soft started of course) and use the Delay timer to Flip Flop access to Transmit,
    Currently you can accept the signal from the Amp key at any time. I will make this an INPUT logic level that will be controlled by the Timer , If the Timer is running, (555 output HI) a gate will decide if it is OK to allow PTT during that 1 minute warm up period. However, if there is an Emergency, I need to BYPASS the amp entirely.
    Anyway, more 4011s to solve the Glitch issue. I do like that 4093 Shmidt trigger Flip Flops so will investgate that as well.
    Back to the Drawing Board.
  3. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    This does away with the offending Flip Flop entirely, and I can repurpose those gates. SO the HV and Screens will come on after the START button is pressed. The previous FlipFlop gates will now route the TX signal to enable transmit ONLY after the warmup
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Make sure cutoff bias also comes on, not just B+ and screens.

    The grids should see around -140Vdc or something immediately, until you transmit when that should be reduced to about -55Vdc for AB1 or -90Vdc for class C.
  5. N2EY

    N2EY Premium Subscriber QRZ Page

    A suitable control and protection system for a 4CX250 amplifier is actually pretty simple. Just requires some relays (which are needed anyway) and a bit of circuit design. Such a system will be simple, rugged, dependable, and RF-immune, without a whole bunch of unnecessary doo-dads gumming up the works.

    Trouble is, such a design requires......actual design.

    Sometimes you get there faster if you slow down.

    73 de Jim, N2EY
    WA7PRC, N2SR, W7UUU and 1 other person like this.
  6. KF5FEI

    KF5FEI Ham Member QRZ Page

    When all you have is a hammer, everything looks like a nail.
    K9ASE, WA7PRC, KS4W and 2 others like this.
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Damn! I always thought the saying was, "When you're hungry for escargot, everything looks like a snail.":(
    K9ASE likes this.
  8. N2EY

    N2EY Premium Subscriber QRZ Page

    "When you don't know where you're going, any road will take you there." (George Harrison)

    "Engineering is doing for a penny what any fool can do for a pound."

    "The more complicated the plumbing, the easier it is to stop up the drain." (Montgomery Scott)
    WA7PRC and N2SR like this.
  9. KS4W

    KS4W Ham Member QRZ Page

    N2EY likes this.
  10. WA7PRC

    WA7PRC Ham Member QRZ Page

    Also, "There's a tool for every job and
    any tool can be used as a hammer."
    - my friend Arne
    K9ASE and AF7XT like this.

Share This Page