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relay sequencing outta time...problem???

Discussion in 'Amateur Radio Amplifiers' started by N2RDQ, May 25, 2018.

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  1. N2RDQ

    N2RDQ Ham Member QRZ Page

    I'm doing some work on a dentron mla-2500.

    one of the clean upgrades is a Harbach pc-2500 supply boards that upgrades PS caps to modern ones and updates / include other circuits that share the boards that they replace.

    one of those shared items is the Cathode bias relay. The new one has a close time is around 5-6ms were as the transmit/receive open frame relay ( T/R is one relay) is 15-20ms and key at the same time, so the cathode will be active at least 10 to 15 ms faster (there is no sequencing built into the design other than relying on the close times of the original relays)..

    I understand that this is out of sequence but will it cause problems?
    do I need to build a delay circuit for the Cathode relay?
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd think it shouldn't matter. You can bias the amp into "transmitting bias" 24/7 (never cutting it off at all) and that shouldn't hurt anything as long as you don't drive the tube with RF.

    Many "old" amps had no provision for cutoff bias switching at all -- just "idled" the tubes with operating bias continuously. The disadvantages of that were only "wasted power and a higher electric bill" and possibly "noise generated" by the tubes which would interfere with reception.

    But it certainly didn't hurt the tubes.
  3. N2RDQ

    N2RDQ Ham Member QRZ Page

    Ah ok, then it sounds like nothing to really worry about.
    As long as it's not going to hurt the amp or the transceiver.

    looks like all I'll need to set the transceivers delay to over 20ms, and she'll be right, as the Aussie's say.
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    A she may take a bit longer to respond to your command. :p
    N2RDQ likes this.
  5. N2RDQ

    N2RDQ Ham Member QRZ Page

    True, perhaps not as quick to respond as her contemporaries, but, she will leave you with a smile every time as long as you treat her right. :D
    KA9JLM likes this.

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