Wurlitzer 1015

I have restored this and it has worked fine . I dont use it much now . I used it last week and all worked , but if i select another song while its playing i get a loud ''crunch'' sound from the speaker when i push a button .

Have you checked all of the connections? You may be arching, and getting feedback.
I am by no means, an expert.

Ken,
First thing I would try is, removing and re-seating ALL "plugs"--(and tubes in the amp). Ron Rich