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Thread: Plate transformer

  1. #1
    Master Navigator kom's Avatar
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    Plate transformer

    I inherited this transformer, it weighs 45 lbs and the secondary resistance is 76 ohms.



    It came out of a transmitter that had 2 X 2cx-250B in the final and, 2 of the same tubes as a modulator.


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    450A @ 2500Vdc?

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    Volcano Tamer PA5COR's Avatar
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    There is a . in front of the 450 so 450 Milli Amps.
    total 4300 Volts at 450 milli amps.
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    Quote Originally Posted by PA5COR View Post
    There is a . in front of the 450 so 450 Milli Amps.
    total 4300 Volts at 450 milli amps.
    Ok. Thanks.

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    'Grumpy old bastid' kb2vxa's Avatar
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    No, 2500V @ 450mA each side of CT when feeding a full wave rectifier with a choke input filter you get 1800VDC at full load, 225mA when using the total secondary in a full wave bridge or doubler configuration. Maybe a dumb question, what's a 2CX250B? The first figure indicates the number of electrodes, the C is ceramic (the X alone is glass) and the last figures are plate dissipation. Methinks you meant 4CX250B, a very common ceramic forced air cooled VHF tetrode.

    That's interesting, two modulating means AM, rather strange for Motorola. What kind of transmitter did you yank that out of? By the looks of the plate transformer and tubes I'd say about 500W RF outpoot, the modulator alone is capable of 500W audio so the tubes just loaf along. It must have some fairly hefty mod iron so you wouldn't happen to be an AM Gangsta now, wudja wudja wudja?
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    Master Navigator kom's Avatar
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    Quote Originally Posted by kb2vxa View Post
    No, 2500V @ 450mA each side of CT when feeding a full wave rectifier with a choke input filter you get 1800VDC at full load, 225mA when using the total secondary in a full wave bridge or doubler configuration. Maybe a dumb question, what's a 2CX250B? The first figure indicates the number of electrodes, the C is ceramic (the X alone is glass) and the last figures are plate dissipation. Methinks you meant 4CX250B, a very common ceramic forced air cooled VHF tetrode.

    That's interesting, two modulating means AM, rather strange for Motorola. What kind of transmitter did you yank that out of? By the looks of the plate transformer and tubes I'd say about 500W RF outpoot, the modulator alone is capable of 500W audio so the tubes just loaf along. It must have some fairly hefty mod iron so you wouldn't happen to be an AM Gangsta now, wudja wudja wudja?
    Typo!


    Output section had two 4CX250B and, it did have a modulator, with two 4CX250B tubes.

    1250 volts on each side of CT, 2500 volts total; I ran the output into a FWB, slowly brought it up to over 3300 vdc with variac. I stopped at 3300 because I didn't trust my capacitance bank, still had more range to go on the variac.

    I am not sure what type of transmitter (brand or model), I was hoping that someone had run across a X-former like this in the past; I found a little info on the Triwec Transformer Company but, not spec on details on their products.

    In my experience, a 1250 vac transformer weighing 45 pounds will supply more than 225 milliamps.

    Here's what the experts (W8JI and WB2WIK) had to say:

    http://www.eham.net/ehamforum/smf/in...topic=104455.0

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    Pope Carlo l K6BSO's Avatar
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    Quote Originally Posted by kom View Post
    Here's what the experts (W8JI and WB2WIK) had to say:

    http://www.eham.net/ehamforum/smf/in...topic=104455.0
    If you've asked The WIK, why bother asking anyone else? After all, he worked in Ott Blthy's lab and was his close personal friend.
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    'Grumpy old bastid' kb2vxa's Avatar
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    The WIKster was the only one who got it right, so to quote Joe Dolce; ah shaddappa you face. Is that what's troubling you Bunky? Well hold your head up HIGH, take a walk in the SUN, and never give up, never give up, never give up that shiP (he always popped that P) and keep poking the burning WIK. Never mind the 1800WV when the important one is the 4,000V hipot test rating.

    "Typo! Output section had two 4CX250B and, it did have a modulator, with two 4CX250B tubes."
    Yeah, I know my tubes and sometimes one needs cleaning with a sharp stick like the one I poked you with just for giggles.
    "...I ran the output into a FWB, slowly brought it up to over 3300 vdc with variac."
    Like every vacuum cleaner in Britain is a Hoover every variable autotransformer in America is a Variac. Mine is an 8A Powerstat but I digress. That's where Baron Von WIKster was right, that arrangement is just fine for a grounded grid 3-500 but 4KVDC is skimping just a bit on the filter caps working voltage. I'm not too keen on balancing out a bank of electrolytics when higher voltage oil filled bathtub caps that work great in a swinging choke input filter take up far less space and can be found at almost every hamfester.

    Naturally WIKster goes off course again, if a 4CX250B can only take 1KV anode voltage in Class C plate modulated AM service why did the transmitter supply them with 1800 volts? My figures are more like it, they came straight off the ratings sheet because I never assume anything. You know how it goes when you assume, you make an ass of yourself in front of me... ASS U ME. I also said they're common VHF tubes (up to 500MHz) because I sure saw enough in that service.

    "In my experience, a 1250 vac transformer weighing 45 pounds will supply more than 225 milliamps."
    ICAS yes with sufficient cool down time, CCS no.
    "New Jersey, the most American of all states. It has everything from wilderness to the Mafia. All the great things and all the worst, like Route 22."
    Jean Shepherd K2ORS (SK) & WOR radio personality

    If you want to fly with the eagles don't run with the turkeys.

    73 de Warren KB2VXA
    Station powered by atomic energy, operator powered by natural gas.

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