[Drake] R4C issues

[Martin Sole]

Dear Drake-ites,

Amongst a couple of other things I have been cleaning and recovering a long
forgotten R4C belonging to a good friend. The radio is a fairly late one, I
think, serial number is 29K. Having removed most of the grease and dirt that
was all over the chassis and carefully going through the radio it now
performs very nicely and is going to make a super receiver for its owner to
add to his other equipment. I will make a start on the matching T4XC
hopefully soon. There are a few small things missing from the radio and I
would like to find them if possible to complete the project.

AF gain knob, this is the one that has the smaller diameter shaft.
Finger spinner for the pto knob (Don't know what else to call this)

Any help sourcing these two small parts would be much appreciated.

In going through the alignment of this radio I did find a very interesting
problem in my own R4C, also a late version. I had thought that my 500Hz
filter was bad but from trying this in the other set I can see it is okay.
What I now believe to be wrong with my own R4C is something to do with
modifications at the 3rd mixer. This had been modified by moving the crystal
oscillator from the grid to the cathode and dc coupling the output of T6 to
the grid of V4. In this state it seemed that the 500Hz filter had very high
insertion loss. Adjusting T6 gave an improvement but in the SSB position
there was oscillation and a constant S9 plus signal indication without any
applied signal. Having examined the other R4C I have here which performs
very well with any filter I have changed the wiring back to that shown in
the schematic. The radio seems to work better but there is still some
interaction with T6 and the selected filter such that it cannot be set to
give the same resting S meter position or signal level for a given input. In
addition I now have a rather strange noise evident in the background at all
times. Wonder if anybody has come across similar problems or has some idea
on a way make it better.

73
Martin - HS0ZED