Al-1500 plate tune cap dimensions

Discussion in 'Amateur Radio Amplifiers' started by KN4CTD, Jan 12, 2020.

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  1. KN4CTD

    KN4CTD Ham Member QRZ Page

    I know. I gave up and sold it all, but I had all the components to assemble a Yc-179 multiband amplifier using two vacuum variables and bandswitched inductor taps. It would’ve been my first amplifier, but I did right by myself all except for selling it all. Now that I know more about what I’m doing, I wish I would’ve hung onto all that stuff so I could’ve finished it at a later date. I really don’t like the thought of cranking on a turns counter, but like you said, you probably never have to worry about arcing a properly rated vacuum cap.
     
  2. WA7PRC

    WA7PRC Ham Member QRZ Page

    In the AL1500 manual I found, C19 is the PA Tune capacitor, and identified as pn 204-2570. Ameritron's website shows the current pn = 282-2570. MFJ's 2019 catalog (page 84) shows pn 282-2570:
    Cap = 20-171 pF
    VRMS = 3.5 kV
    Plates = 37
    Plate Spacing = 0.120"
    Dimensions = 2.8W x 2.6H x 7D
     
  3. KN4CTD

    KN4CTD Ham Member QRZ Page

    The current info online is all I had access to. But, the schematic online has C19 listed as a 4500v cap. I want to start laying this rf deck out, but I would hate to waste my time drilling holes to mount a cap that won’t be sufficient for the job. Thanks for the extra info. IMO, Ameritron could do a little better with their parts descriptions and keeping their schematics up to date
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    I quoted info from the current MFJ catalog. Note that it specified VRMS. VPEAK = VRMS x 1.414. In this case, that would be 3500 x 1.414 = 4950V.
     
  5. KN4CTD

    KN4CTD Ham Member QRZ Page

    Ok, I didn’t see that the first go round. I guess that plate spacing is very close to being in line with the ARRL handbook voltage/spacing numbers. I think I’ll just call them tomorrow to verify etc. Deciding on a suitable plate cap has been holding me up. I wouldve liked to had the output tank, tube socket, etc done by now but I can’t decide on a suitable plate cap
     
  6. KN4CTD

    KN4CTD Ham Member QRZ Page

    If I we’re gonna build my own enclosure, it would be a no-brainer. I’d just use that huge cap Palstar offers. I just hate doing major sheet metal work so I bought an enclosure pre-built. I either gotta find something to fit nicely inside it or back up and punt
     

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