Hi All,  The check valve in the vacuum pump box of the Aeolian Sting II
player piano is a spring-loaded valve that is located in a lead casting
to which four plastic valve blocks are glued (see attached graphic).
Detailed pictures at the link below show exactly where the valve is
located.

https://www.player-care.com/pump-box.html 

With regards to problem Rick Hageman explained in his posting [201031
MMDigest], the reason I said that the problem didn't sound like it
involved the check valve is because he also said, "....however, there
is a massive loss of suction and the roll will not play when I turn on
the switch."

So, if the check valve was stuck closed, there would be no vacuum loss
through the suction box when foot -pumping. And, if it was stuck open,
the system would get all the vacuum that the pump was able to produce.
Ergo, I said that the problem most likely wasn't the check valve.

In closing, due to the relatively crude design of the check valve
and the relatively weak spring used to keep the valve closed, it is
possible (although rare) for the valve to fail. However, getting to the
valve to repair it is not a simple task -as can be seen in the pictures
in the web page listed above.

I should also mention that of the 500+ Aeolian players I've worked on,
only one had a stuck valve (stuck closed), and the problem was resolved
by applying a drop of Marvel Mystery Oil on the valve guide pin and
pushing the valve down a few times until it moved freely. (I still
don't think that's Rick's problem.)

Musically,
John A Tuttle
Player-Care
Brick, NJ, USA

 [ Aeolian Sting II Check Valve location
 [ https://www.mmdigest.com/Attachments/20/11/05/201105_215453_aeolian-pump-box-check-valve.jpg 
 [ Check Valve (close-up)
 [ https://www.mmdigest.com/Attachments/20/11/05/201105_215453_pump-check-valve.jpg