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I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.

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The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).

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My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.

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Many thanks,

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-Mark