Discussion in 'Amateur Radio Amplifiers' started by KC1DX, Aug 23, 2019.

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  1. KC1DX

    KC1DX Premium Subscriber QRZ Page

    Hi anyone .
    Someone have the ALS-500 technical service manual they could share or sell.
    I have high SWR problems at 10m to 20m between radio and linear.
    The another band's work perfectly.
    Mauro KC1DX
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't recall Ameritron publishing any service manuals for any of their amplifiers, including that one.

    You might call them to confirm, but I've owned a few and never found any service manuals; but they do have complete schematics and parts lists in the regular owner's manuals.

    The ALS-500 has a 6 dB resistive pad (attenuator) wired right to its input, before the splitters that drive the four 2SC2879s, so if those resistors (and the compensating capacitors, C221-C224) are all okay, no matter what happens beyond that point the input VSWR could never be >3:1 (even if following that is an open circuit or short circuit).

    What does the input SWR measure on 10m through 20m?
  3. N7WR

    N7WR Premium Subscriber QRZ Page

    Manual is available on line at the MFJ website
  4. KC1DX

    KC1DX Premium Subscriber QRZ Page

    At website just has the USER Manual .
  5. KC1DX

    KC1DX Premium Subscriber QRZ Page

    The SWR are 2 to 3 on 10m.
    and 1.5 on 20m

    If you have time take a look in this video I make

    I change already C221 to 224 and mesure all resistor .all good ,just remember I used this amp long time using in 100w.

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