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MMD > Archives > January 1997 > 1997.01.02 > 11Prev  Next


Re: Ampico Anomalies
By Craig Brougher

Regarding my question about Frank Himpsl's model A, Robbie mentioned this:

>[ My Ampico B had similar anomolies before it was rebuilt. I think
>[ that when the vacuum rises slowly, as when the motor is turned on,
>[ the valve logic doesn't "follow the normal rules." -- Robbie

The operative term is probably, "Before it was rebuilt." Let's continue our discussion, because I believe we agree. We are just saying it differently. Robbie, I said that after vacuum comes up to normal, the valves do not stay confused. After all, if they did, no Ampico, Duo-Art, or anything else pneumatic could ever work right since that's how they all start up. Everything gets a-goin' at one time. The suspended valves, the packing leaks, the air motor -- they all start together with the pump. That's why you need cancels before the music starts, to make sure you don't have an expression standing up to start out on.

Robbie said:

>[ I believe that the explanation above is true only under the
>[ manufacturer's "Recommended Operating Conditions", Craig. Nobody
>[ expects TTL logic to operate to specs at lower-than-normal voltages,
>[ and the same should be true for binary pneumatic logic.

Of course that's true. That isn't what I was saying. You recall, Frank Himpsl's piano was able to maintain a strong playing level for 88-note rolls, if he were to simply press down his manual level buttons first, then when it got going, he switched his automatic switch to Ampico OFF. It stayed up the full trip, apparently. That is my question, not whether valves will operate reliably before the pump pressure is up to speed. If I misstated myself somehow, let me know.

Then Robbie said:

>[ Unless special provisions for "Power-On Preset" are included in the
>[ design, the logic state following Power-On is indeterminate. That's
>[ why, for example, all Ampico and Welte rolls have "Cancel Intensities"
>[ commands before the music begins.

Here is where we may differ, I don't know. In the Ampico B, the piano always stops its reroll on "Replay." That allows you to simply hook the tab of the next roll and turn it on. The trackerbar isn't covered yet. Also, leaders sometimes tend to be stiff or wrinkled and actuate expressions all by themselves before the music plays. There was a glue seam on original rolls which often uncorked expressions in an unpredictable way. But by the time the leader was past, the pump was well up to speed. Then comes the cancel holes to drop any expressions which may be standing. However, this does not continue throughout the roll, as TTL logic or Frank's Ampico might do.

The problem was really never pump vacuum but leaders. The second the pump motor starts and makes a couple of turns, you're up to speed. That happens quicker than it takes an air motor to start turning. I don't even want to guess what the valves may be doing during that one-second start-up. All I know for sure is that they are at least not _permanently_ confused. Finally, Robbie said:

>[ I have no faith in a control system until after the power supply has
>[ stabilized, and the proper initial conditions established.

And my reply to that is, "Amen, brother."

Craig Brougher

{ "Amen, Craig!" -- Robbie ]


(Message sent Thu 2 Jan 1997, 18:01:31 GMT, from time zone GMT.)

Key Words in Subject:  Ampico, Anomalies

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