[HAM] Motorboating noise has returned even though the vibrato scanner stator plates and the phenolic spacers have been cleaned and sprayed with enamel

[Kon Zissis]

Hi everyone.
Two and a half years ago my friend's 1959 C3 was producing a very loud
choppy  motor boating type noise and zapping the switches and the wires
would temporarily stop  the motor boating noise but the noise would
eventually return so therefore my friend got me to open up the vibrato
scanner to clean it and seal it with enamel.
 
The  square shaped phenolic  spacers from inside the vibrato scanner and
the round shaped phenolic spacers outside the vibrato scanner  had
absorbed oil over the years so therefore  I cleaned them by soaking them
overnight in Shellite solvent. The next day after they were clean and
dry , I then  thoroughly spray painted them with White Knight Rust Guard
epoxy enamel paint.
I also  spray painted  the  stator plates and the inside of the case of
the vibrato  scanner . I gave the phenolic spacers and the stator plates
and the inside case of the vibrato scanner  three coats of paint so that
the enamel would thoroughly seal  all these.
 
After I reassembled the vibrato scanner , it worked properly and it was
completely free of the motor boating noise for the last two years.
However in the last few months  the motor boating noise has gradually
began to return and it is  now starting to get loud and it has become a
nuisance.
 
Last week I thoroughly zapped the vibrato scanner wires and all the V,
C1, V2, C2, V3 , C3 switch positions and both of  the vibrato tablet
switches in the vibrato on and off settings  with the B+ voltage of the
AO28 preamp and this stopped the motor boating  noise , but yesterday at
our band rehearsal the motor boating noise has returned and it was loud.

 
Does anyone know if the oil in the vibrato scanner can still cause a
partial short circuit that would create the motor boating noise even
though the stator plates and the phenolic spacers are sealed with
enamel ?
 
I have not yet opened up the drawbar base and the vibrato switch
contacts  because the owner has not yet authorised me to do this but I
think that I might have to do this and then inspect all the contacts and
then clean them if there are dendrites on them.
 
The  tone wheel generator has only been oiled twice since I repaired the
vibrato scanner two and a half years ago, and the amount of oil that the
owner has used is less than what is recommended  on the oiling
information plate that is next to the oiling funnels.
 
Is it possible that oil build up inside the vibrato scanner can still
cause the motor boating noise to return even though all of the phenolic
spacers and the rotor stator plates  and the inside case of the vibrato
scanner have all been thoroughly sealed with  the epoxy enamel spray
paint ? 
 
Thank you in advance for a reply.
All the best.
Kon
.