cd8e1f53   
   XPost: sci.electronics.repair   
   From: legg@nospam.magma.ca   
      
   On Mon, 30 Jul 2012 11:17:58 -0700 (PDT), spamtrap1888   
    wrote:   
      
   >On Jul 30, 11:01 am, legg  wrote:   
      
   >> The non-functioning mixer self-biases at half the schematic grid   
   >> voltage value and 2/3 the plate current - but  expect this when input   
   >> signal is missing Grid resistor is 20% low with age/dirt. Oscillator   
   >> grid resistor seems low in schematic at 22K, but what do I know.   
   >>   
   >> As this is the section that seems to be malfunctioning, I'm wondering   
   >> if there's any advice related to the earliest versions of this tuner   
   >> that might ease in reviving it. Tubes test functional for heater,   
   >> emissions and transconductance, if a little slow to warm up.   
   >   
   >Just to clear the decks: I'm assuming there are no date codes on   
   >chassis or PCB that would indicate early or late production, and that   
   >the tube types present match the numbers silkscreened on the PCB, or   
   >the tube diagram inside the unit, if present.   
      
   No room for tube diagram. Chassis cover is perforated, chassis base   
   has standoffs and adjustment ports. This is pre-silkscreen era -   
   copyright 1956 in foil pattern.   
      
   Just seeing a printed circuit in consumer audio surprised me.   
      
   Board is PC-A-5, DWG P1702265A   
      
   MFR 'Operation and Service Instructions' dated 1956 stops at page 4,   
   without a tube list or schematic. SAM's is dated 1957.   
      
   RL   
      
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