frequency/channel light is out on stock radio/cassette. Any idea if it can
be replaced?

 

doubt it......most of these older Volvo radios were put together by Alpine and made with Mitsubishi parts. What does that mean? Volvo would just replace the radio instead of the burnt out light. Check ebay for a new one....sometimes you can find Volvo OEM radios cheap/rebuilt.

I suppose if you're "circut board savy"...you could try to take it appart to fix it.