[Collins] problem with Collins 30L1

[fkamp at comcast.net]

fkamp at comcast.net wrote:
> I am trying to interface a 30L1 to an ICOM 737.
> 
> I got the -170 volt antenna relay line taken care of with
> a relay.  No connection to the ALC.
> 
> With 70 watts RF input to the amp, I get no output.
> Well, maybe just the barest of meter needle movement of
> the watt meter on the 0-200 watt scale.  The barest of
> movement does  have a barest of peaks when the plate tank
> capacitor is tuned to frequency.  No indication of plate
>  current and the 811As all have -30vdc on the grids.  (I
> was expecting the grid voltage to be zero on transmit but
> I dont know what it should be on a working amp.)
> 
> I have checked the following:
> 
> HV at 1800vdc as indicated on the panel meter
> 
> plate rf choke good
> 
> All fuses good including the 1 inch #20 wire from the 
> filament ct to ground.
> 
> Bias supply running at -170vdc
> 
> Service bulletins 1,2,and 3 mods installed.
> 
> Service bulletin 3 puts a 2k 7w resistor across the
> antenna relay coil, adds a 39 ohm in series with the
> relay line (which is switched to ground) and changes R9
> in the bias supply from 82ohm to 47ohm.
> 
> All resistors have been checked for value.
> 
> All capacitors have been tested for leakage and shorts.
> 
> All diodes have been tested and none are shorted or open.
> 
> 
> Currently running a brand new matched set of 811s
> purchased from Ameritron.  The amp did the same thing on
> the old set of RCA 811As.
> 
> I am hoping that this is a common problem on these amps.
> Something easy to fix.  The only fix I can think of is to
> wire the grid bias circuit so that grids are at -170
> during receive and at zero volts during transmit, but
> that would mean changing the circuit from what shows on
> the official schematic.
> 
> Any help will be appreciated, Frank Kamp K5DKZ 
> ______________________________________________________________

Ah-Ha!  There it is!  Aint technology wonderful?  It only 
took 48 hours for this message to make it through to a posting.

The amplifier problem was caused by no voltage on the tube 
plates.  Oh there was high voltage.  The meter showed 
1800vdc but due to a broken wire it was not getting to where 
it was needed.

All fixed now.  Works great.  The 30L1 is a wonderful amp.

Regards,
Frank Kamp