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AL-811H Relays

Discussion in 'Amateur Radio Amplifiers' started by G3YRO, Dec 6, 2019.

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  1. G3YRO

    G3YRO Ham Member QRZ Page

    The MFJ Ameritron AL-811H amplifiers use a pair of black sealed 12V relays . . .

    I've replaced them before when repairing thse Amps. (the bias contacts often burn out, presumably due to a valve flashover)

    I thought I had bought them from RS Components here in England . . . but looking at old orders, it appears I didn't.

    I have tried wading through all the hundreds of relays on various websites, and can't find anything similar !

    Has anyone found a source of these, and part number, that I can at least cross reference?

    Roger G3YRO
  2. KD0RCB

    KD0RCB Ham Member QRZ Page

    Roger, have you tried calling Ameritron directly? ( The manual with part #s are avalible on their website)--They are very helpful, and often times a Tech will answer the phone....Also, have you checked DIGIKEY.COM ? They have 1000's of relays and specs avalible, and are very helpful also for hunting down & and cross-referencing parts, etc. Good luck, Randy.
  3. MM0IMC

    MM0IMC Ham Member QRZ Page

    Whilst the Ameritrons are initially cheap over here in the UK, they are a sod to get parts for! It costs and arm and a leg to get stuff shipped over from Ameritron, unless you are lucky enough to source some equivalent parts this side of the pond.
  4. G0GSR

    G0GSR Ham Member QRZ Page

    Roger have a look at W6PQL's site.
    He has done some good testing on common relays when used for RF.
    You can get the 16A relays from Farnell.

  5. G3YRO

    G3YRO Ham Member QRZ Page

    The trouble is I have spent ages trawling through websites like Farnell, RS, Mouser, looking at over 500 different relay types on each site, and haven't managed to find any the correct size !

    I THOUGHT I had bought them from RS before, so rang them to look at my back orders, to tell me the part number . . . but it appears I bought them elsewhere.

    They are quite unusual . . . more than twice as long as the normal sealed relays . . . and need to be the correct size as they solder onto the PCB.

    If anyone has any info, do please post on here !

    Roger G3YRO
  6. W1BR

    W1BR Premium Subscriber QRZ Page

    Hello Rodger!

    Are these the relays (scroll to photo or relay board): QSK vacuum relay modification.pdf

    The ones shown are 24 VDC, but they are made in voltage ratings from 5 volts and up... I have read that some manufacturer versions may have better
    RF voltage handling. You could check on the IO group amplifier forum for more detailed answers:

    They are very common relays in the US. Here is the Newark page for the RTE24012F:!p!!g!!rte24012f&CMP=KNC-GUSA-SKU-MDC
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Thanks for the help . . .

    Actually, having looked at the actual relays, they are not as long as I remembered ! (I must be thinking of some other equipment with a strange long black relay)

    So I have discovered that these Relays ARE readily available from RS, Farnell, etc after all . . . . so I have ordered one.

    While just doing some resistance checks on this Amp, I notice that the resistance to ground from each Grid pin is only 7 ohms . . . whereas the circuit diagram shows 51 ohm resistors.

    I haven't bothered removing the sub-chassis to look at these resistors . . . but is this a Factory change, does anybody know?

    Roger G3YRO
  8. K8YOY

    K8YOY Ham Member QRZ Page

    Roger,with or without any modification, can you use the RTE24012F relay to replace BOTH relays in the AL 811 H?
  9. N8VIL

    N8VIL Ham Member QRZ Page

    Deleted. I see you have sourced a relay.
    Last edited: Jun 28, 2020
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    AL-811H's manufactured in the last few years have the grids directly grounded, no resistors.

    The very early models did not use sealed relays, they used one 3PDT open-frame relay with big contacts and were quite reliable.

    No clue why they changed that, it must have saved a dollar or something.:)

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