Brooks asked me to look this over. I hold Steve's opinion/advice with high regard, but I was unaware that the diode affected operation of the radio. I was pretty sure the radio operation would quit when the ignition was turned off due to the ignition being shut off, but would resume operation if the radio button was pressed because of the constant supply that was available for memory power. I am (or at least was) sure that the diode was only for power seat operation with ignition off/door opened. I
haven't gone back to my 201 CD to look at the radio diagram (Brooks didn't tell me it was a radio problem, just asking about the location of the seat diode).
In short, in looking at my 201 wiring diagrams, it looks to me like 89 was the last year the 201 had the diode, at least for power seat operation. After that, it appears the power seat relay handled it all itself without a diode in the system.
My gut reaction to the radio problem is that the radio is bad, possibly because of the arcing that took place.