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MMD > Archives > October 1997 > 1997.10.14 > 16Prev  Next

Ampico B Drawer
By Craig Brougher

Randy Hayno was asking about the drawer circuit of a Knabe Ampico
model B.  I can't say that I'm very impressed with any of the circuit
modifications on any of the model Bs.  The reason these are usually done
is because they can't seem to get them to work, otherwise.

Sometimes the problem is pump pressure.  And very often, the reason for
the low pump pressure is not only leaky bellows and flap valves, but many
tiny leaks throughout the system.  For example, when you still find the
original "burnt" shellac around the valve blocks, you can be assured that
they have not been disassembled, and so still have their original
pouches, which are by now stiff, due to the rubber cement sealant the
factory used on them.  And "B" valve blocks all have a phenolic inside
valve seat that leaks, if it hasn't been removed, scraped, and reglued.

That said, Randy asked:

> I had to remove the loud pedal block to get it out.  What size and
> threads are these nuts???  My thread gauge doesn't have anything to
> fit it.  Does anyone supply these and the spring clamps?

You might check with Robert Streicher, who is able to make anything you
may need for the Model "B." He may even have them in stock.  His number
is 717-559-7403.

> Also in the drawer there was a modification made to the Control Valve
> Block.  My block is different than the one in the book.  It has a
> separate nipple to feed the reroll valve "A"  on top.  The book shows
> that valve is fed from the side from pedal suction along with the
> tracker and music roll brake.  There is one more nipple on my Control
> Valve Block than the one in the book.

That is not factory.  You only need one nipple supply to feed both valves
A and the music roll brake line, tracker line, etc.  Notice too that the
supply there comes from "pedal suction." That may mean your pedal vacuum
regulator is set too low, for one reason or another.  It should be set to
about 18-1/2 to 20".  The reason for the regulator is to prevent the
pedal from operating on amplified pressures.

> The modification I found is that the nipple that is supposed to feed the
> music roll brake was plugged and the brake was fed with a separate tube
> from a tee at the pedal pressure test block.  I'm not sure this is an
> original mod since this tube ran around the stack.

It does exactly the same thing, but why not put it back like it's
supposed to be?  You might discover another problem in the meantime --
why they had to do it in such a round-about manner.

Craig Brougher

(Message sent Tue 14 Oct 1997, 17:35:25 GMT, from time zone GMT.)

Key Words in Subject:  Ampico, B, Drawer

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