Duo-Art Playing Too Loud
By Pete Knobloch
Thank you for your responses.
I have just ordered a Vacuum Gauge. I haven't needed one until now.
SLOWING DOWN PUMP MORE: This weekend I found a pulley that was made for a larger belt width and tried it. It made a large difference in the pump motor speed. The RPM on the pump went from 90 RPM down to 70 RPM. The piano has problems playing properly without making other adjustments but when I Manually hold the spill valve up on the expression box it plays fine. I don't intend to run the piano with this pulley because the Auto Replay function doesn't work properly because of the sluggish delay seen when the hole is opened on the bottom take-up spool. The auto shutoff also has problems. This may be another problem but I will have to see what the vacuum gauge reads when I get it.
The pulley that originally came with the piano was 2". The pump ran at 102 RPM with this pulley. I did find an old Duo-Art service manual from 1927 that states that the RPM value on the pump should be 120 to 125 RPM just as Spencer stated. I have noticed a slight lag problem and the piano running out of air on one spot when playing "American in Paris" when using the pulley that runs at 90 RPM.
Another affect that I noticed was that the spill valve had a greater affect on the playing volume when the pump was operating at a lower vacuum level than at the higher level. This may be because more percentage of the total air is being lost thru the spill.
At this point I know:
1) That the 2 springs are original with correct tension. I have compared it to a 2nd regulator. The Theme regulator has the stronger spring.
2) Leakage because of using the Cross valves may be a problem. I didn't touch these valves when I changed the pneumatics. I will check this using the procedure described by Craid B. when I get my vacuum gauge.
3) The accordion closures are working properly when viewed at the regulator. No funny tubing errors.
Note: One thing new that I have noticed while viewing the regulator while on the floor is that the exponential loudness problem is happening when the accompaniment accordion is closing all the way. The more I think about this, I may just have a problem where the accompaniment volume is greater than the Theme when playing loud and they cross at bad points. I started looking at the Accompaniment holes in the roll and saw this correlation for the first time. I reduced the travel distance for the accompaniment and the exponential loudness problem has gone away. Where is that vacuum gauge!
4) The theme valves seem to switch OFF properly. When manually increasing the theme volume from the front panel, the keys that are played with expression are played very loudly. All others play at the lower accompaniment (background) level.
5) The Room that the piano is in has wall to wall carpet. The hammers may be hard but I don't think they need immediate work at this time. At some point I need to remove the keybed for the first time and fix other problems such as hammer knuckle cleaning, increase the travel of a few of the bass dampers and will try things like water and Alcohol on the hammers to soften the felt striking area as suggested by Larry Fisher. I like the player action work more than the piano side of this hobby. It seems that I'm doing more piano work like sound board repair, string, pin and hammer replacement.
At this point I am going to start looking into the spill valve adjustment and Mufler Felt hole as talked about by Spencer C. and Craig B. I did make a small change to it (but don't remember when) that increased the opening when playing at low volumes. My thinking was probably wrong when I did this change. I thought that letting more air in at low volume would also let more air in at the loud volume. In reading information that was received from FOXTAIL I think that I may have caused a problem. I forgot to mention this in the original document.
I may be letting in too much air into the spill value when playing at the softer volumes. This may be causing me to set the 0 adjust to a higher value than necessary. When the accordion pneumatics close down, the air in the spill is also closing which pulls even more air thru the regulator. This should be a fairly easy change to make and see how the loudness problem is affected.
The small service manual does mention "OPERATION OF THE ATMOSPHERE INTAKE OR SPILL". It says to adjust this valve to close off completely when power #10 is required by either accordion pneumatics.
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