First off, I'm sorry to say that I can offer no help regarding the
connector ribbon.  There is one thing of which I'm fairly sure,
however.  If you truly have a crystal pickup at the end of the reverb
line there is a very good chance it is dead.  Salt crystals do not age
well and it is very common for them to fail after a number of years.
The delay in my much later A-100 uses a magnetic pickup and if what you
believe to be a crystal pickup is actually magnetic then, of course,
the question doesn't arise.

If the crystal has indeed failed then you will probably need to work
out another method of sound pickup at the end of the delay line.  This
could alter the qualities of the connector ribbon needed and perhaps the
level of amplification needed in the reverberation amplifier.  I have
a feeling that there's nothing particularly special about that connector
ribbon other than to transmit sound to the pickup but I could be wrong
here.

You may wish to consider a modern electronic delay circuit (horrors!).
This could give much more satisfactory reverberation but would lose the
classic "screen-door-spring" quality of the original which really is
part of the fun.

Jim Heyworth,
Sechelt, B.C., Canada