Dear Tom, Greetings from The Bronx.  Regarding your inquiry, first
check to see if these players have the earlier leather faced valve
discs or the later neoprene foam punchings.  If it is the earlier
leather faced valve discs, then it is a quandary.  But, if it is the
latter, as I suspect, then your problem is that the neoprene foam has
begun to disintegrate.

Neoprene will dry out with age normally, but as most players of that
type have vacuum cleaner type boxes supplying the system, it is the
motor that is producing ozone that has advanced the aging process.
A slight leak in one valve alone might not seem or be too troublesome,
but multiply that by possibly 80 valves, and you've got your culprit.

You could replace the valves, but the replacement valves will most
probably be of the type you are replacing, the neoprene sponge type.
Although recently there has been someone manufacturing replacement
valves that follow the earlier type of construction, to wit: leather
faced valve discs.

From what I have seen the valves are of good reliable construction,
but that is at a cost, to replace 80 valves will cost you at least
$1,100+.  And that is just for the new valves and not the removal
of the old ones.  You'd be looking at possibly at least a $2000 bill
for just a valve job (a conservative estimate, your rates may vary).

I hope this has helped.

Sincerely,
Dale F. Rowe
Bronx, New York