{Collins} 30S-1 with negative grid current during standby

I have gotten back to working on one of three 30S-1 I have in the shop.  I
posted a while back about a couple of issues I was having.

One issue was that in the SSB position BIAS voltage was 75 on the
multi-function meter and was not adjustable.  In the CW position it was
adjustable!  Well today I figured out why.  I let the front panel down on
the amp and did the same to a know good amp and it was obvious that someone
had reversed the connections on S201C putting the adjustable BIAS in the CW
position.  I returned the wires back to normal position and all is well
with the grid bias control now.  CW is unadjustable at 75 and SSB is
adjustable from 75 to 25... all is good there.

Does anyone know why this might have been done?  Was there any mod that
this was part of?

I still have one problem that I am working on.  I start with the
multi-function selector in the Grid Current position (all other positions
appear to give proper indications).  The meter is on Zero with the power
off.  I turn the power on and the meter stays on zero, but after about 3 to
4 minutes the grid current goes negative on the meter.  In the CW position
the meter reads a negative  .1ma.  In the SSB position the meter jumps
right to a negative .8 ma.  Neither of the other two amps do this.  I
thought perhaps the 12AL5 in the ALC circuit might have something to due
with it, but after changing it out it does the same thing.  This is all
with the High Voltage at Zero.  It makes no difference if the H.V. is on or
off.  I know that there should not be more then a positive .2 ma during
operation, so I am concerned that I will damage something with a negative
.8 ma.

Any ideas would be great.  So far the CW/SSB switch is the only place I
have found a soldering iron to be used after leaving the factory.

Thanks Greg WQ0P

This archive was generated by a fusion of Pipermail (Mailman edition) and MHonArc.