50's MASCO PA amplifier w/ 807 tubes trouble

Discussion in 'General Electronics Chat' started by jryan, Nov 19, 2011.

  1. jryan

    Thread Starter New Member

    Nov 19, 2011
    ive just picked up a masco ME60, am having a hard time finding a schematic for this particular amp. its rated at 60watts from two 807 end cap tubes. my tech has got the amp right now, and is saying that the plate voltage is really high, up in the 800's, and is not sure if this is normal or not. he says he believes it has killed my filter caps. if anybody has any info on this amp, tubes or a schematic it would be greatly appreciated. J Ryan
  2. jimkeith

    Active Member

    Oct 26, 2011
    I love this one--haven't heard of the 807 beam power tube in years--well suited for amateur HF transmitters--similar characteristics to the more common 6L6--plate is the cap which makes it handy to connect to a resonant tank circuit.

    This is the first datasheet i could find: http://www.g4nsj.co.uk/valves/807.shtml

    And yes, 800V is about double what I think it should be for a class AB push-pull amplifier, but the datasheet shows it can be applied at its maximum voltage (750VDC)--the electrolytics would have to be in series for that voltage.

    You have a bit of history there--hope you get it working OK.