FT 301 Clarifier circuit - problem analysis. Oct 2 2013 --->>> see the simple solution to
the problem that came about (at the end of this page).
V control goes to the
anode of D801 (VC801)
and causes the varactor
diode to change
capacitance in variation
with a variable voltage.
At point "T" you should
be able to measure a
voltage swing
T
1st step is to see if the 6 volts is
present on PB1541B. If the voltage
is larger than 6 volts then a larger
capacitance swing than normal will
maybe occur.

IF 6volts is present then turn the
clarifier on and check the spot
CLARI on the schematic and see if
you get a variable voltage at this
point when varying the control .

It would be a good idea to trace
the wire to the +6 volts back to its
source and make sure the 6 volts
line is working properly..

Other potential problems could be
the 1K resistor and 3.9k resistor.
Check with ohmeter.
vin
SOMETIMES THE SIMPLE SOLUTION IS THE SOLUTION..the fellow who sent me the emails wrote me back
with the solution he found.
Earl,

  Found the problem. Dirty contacts on RL 1901. (PB-1451) Carefully removed cover and gently touched it and everything started working. Sprayed with
contact cleaner.

  Performed the zeroing calibration and now it is fine.

  I want to thank you ever so much for your support and info.

  I hope I don't have any more problems but I certainly will be contacting you in the event.

Greatfully yours, Larry, K8*** (identity protected)..I dont publish names and callsigns for privacy reasons. THANKS FOR THE EMAIL LARRY.

Well..I think Larry solved the problem without much help from me. It didnt occur to me that the relay on the blanking board was involved with
the clarifier circuit. ---
so a good general rule of thumb ..would be to clean the contacts of the problem circuit first. If there is a relay near
by..doesnt hurt to clean the contacts of the relay while you are at it. ---
NOTE: use contact cleaner sparingly and catch the overspray with
paper towels or something.... CAIG is generally acknowledged to be a high quality contact cleaner. They produce a bottle with a small brush
for small jobs. I plan to buy a bottle of this CAIG with little brush for small jobs like these small relays.