[Drake] Drake R4C - Unstable VFO

[Robert Wood]

Hello all,

I believe I solved the issue and wanted to thank everyone for their expertise
and help.

I finally got a chance last night to work on the R4C, because the XYL kept me
busy putting up Xmas decorations over the last few days.  My plan was to swap
the PTOs between the T4XC and R4C and determine if the problem followed the PTO.
As I mentioned in my initial email, when selecting the T4XC as the primary PTO
the stability problems (CW warble) did not occur.  I took the cover off the
T4XC, I noticed "T4XC" stamped on the PTO so I decided to compare schematics.
Well, the two PTO designs are close, but they are not the same HI.

I then decided to turn on the radio and poke around the chassis and components
with a plastic screwdriver (I learned this trick from my High School Consumer
Electronics Teacher, HI).  While listening to a CW signal, I poked here and
there and when I got to the Crystal Switch behind the five crystals I was able
to influence warbling.  I then sprayed the switch with Deoxit while turning the
switch back and forth and the CW signals stabilized.

I have been listening to the radio for several hours this evening and all
appears well.  I guess age finally caught up with the radio (keep in mind I
bought the Twins new back in 1975).  I plan to monitor R4C over the next few
more days before putting it back into production.

Again I want to thank everyone for all of their help and input, I really
appreciated it.

Thanks,

Bob
K5MBA

Robert Wood wrote:
> Hello Drake Techies,
>
> I have a possible PTO issue with my R4C.  When listening to CW on any band,
the
> signal is not stable (tone jumps around) intermittently.  I do not encounter
the
> issue when switching to my TX4C PTO.  When using the T4XC PTO I can work other
> stations with no problems :).
>
> At this juncture, here are the steps I have taken within the R4C:
>
> 1. Cleaned all of the vacuum tube sockets and pins (deoxit)
> 2. Cleaned all of the switch contacts (deoxit)
> 3. Swapped 6HS6s (Premix Tube with the 1st Mix tube) no change
> 4. Replaced the two electrolytic capacitors (C163, and C163)in the 150V power
> supply section. (I thought I noticed the voltage fluctuating so went ahead and
> upgraded the caps)
> 5.  Tightened the VXO mounting screws.
>
> I am thinking about swapping the PTOs between the units to see what happens,
but
> before I do I wanted to get other suggestions?  I really appreciate any help.
>
> Thank you very much,
>
> Bob
> K5MBA
>
>
>
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