Handpiece Control Block

Handpiece Control Block
Handpiece Control Block
(Model #49-87)
The handpiece control block has drilled passages for drive air, coolant air, collant water, and gauge pressure.
Sandwiched between the two halves of the block is the “hold back” diaphragm. When a handpiece is in its holder or
the holder is otherwise locked out, signal air passes through the holder valve and applies pressure to the diaphragm
which in turn closes off the passages to that handpiece. When the handpiece is lifted from its holder the valve closes,
shutting off and exhausting the signal air. This permits the diaphragm to deflect away from the passages allowing air
and water to supply the appropriate handpiece.
Drive Air Adjustment Stem
Hold Back Air In
Water or Water
Signal Out
To Gauge
Turbine Air In
Drive Air to
Water In
or Water
Signal In
Coolant Air In
The above control blocks are designed to provide automatic control of 2 to 5 handpieces when used with similar hold
back air valve. The pilot valve used must supply positive air pressure (80 p.s.i.) when the handpiece is in the hanger.
The supply in and gauge pressure out ports are located on the end. The handpiece ports are on the side. Each
handpiece position is grouped, as indicated by the installed barbs in the above image. The #48-87 can be used for 2 or
3 handpieces. Port layout is the same for all models. Unused handpiece positions must be blocked off via use of 10/32
hex plug and nylong washer.
After installation all air must be purged from the water system. If a position of the block is not used, loosen the hex
plug on the water out port for that position and step on the foot control. Allow water to flow through any unused
ports then replace the plug.
7310 Oxford Street • St. Louis Park, MN • 55426
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Water or air leak
from block.
Loose or defective
Soap block and check for air leak.
If leak stops, no
Tighten loose fittings. Loosen all
further action
screws in center of block first, and then required.
tighten screws around the edges.
If leak continues from
diaphragm, replace.
Also, check inner
surfaces for defects in
the sealing surface.
All handpieces
run at once.
Unit has low air
Check for 80 psi at guage.
Adjust to 80 psi and
recheck handpieces.
Diaphragm defective.
Open block. Check diaphragm for
Replace diaphragm.
One handpiece
will not shut off.
Holder valve not
Remove tubing from holder valve
Replace diaphragm.
where it attaches to the block control
block. Check for air flow when
handpiece is in holder or when valve is
Check holder valve for
operation. Adjust valve
position in holder.
Replace if necessary.
One handpiece
will not operate.
Holder valve not
Make sure holder toggle is down.
Remove output tubing from holder
valve. Air should stop when valve
finger is forward.
No further action
Repair sticking valve
or holder. Replace if
Water drips
from handpiece
when foot
control is at rest
or is slow in
stopping when
foot control
is released or
water sprays
when handpiece
is first picked up.
Foot control
not shutting off
completely or not
Disconnect signal air line to coolant
water toggle. Check for air flow when
foot control is at rest or slow air flow
after foot control is released. It should
stop within one or two seconds.
Go to next step.
Clean foot control
poppet for sticking or
replace valve o-rings.
See foot control section
for instructions.
Water relay or water
relay needle valve not
After determining there is no air
signal to relay, remove output water
line relay. There should be no flow.
Water sprays
from an unused
handpiece when
another is being
For units with purge
system only. Purge
toggle switch is
With the same line disconnected there
should be no flow from the purge
Cross over through
control block
Remove the water tubing on the
control block to the unused handpiece.
There should be no water flow when
another handpiece is used.
No water coolant Flow control valve is
Open flow control fully while running
to handpiece
closed or water toggle handpiece.
switch is off. If unit
has a water coolant ,
switch on foot control,
it should be on.
No air signal to water
relay or water relay
needle valve.
For units
No air signal through
equipped with
foot control switch.
an optional
water coolant
switch on the
foot control only.
No further action
Replace water relay.
Next step.
Disassemble purge
toggle. Check for
debris or worn o-rings.
Clean, lubricate, or
replace as necessary.
Replace the diaphragm.
If water begins to flow,
adjust to desired flow.
Next step.
Disconnect air signal line to relay.
When foot control is depressed, there
should be air flow.
If air signal is present
as well as water,
replace water relay.
Check for pinched or
clogged air supply
between foot control
and relay.
Remove output tubing from coolant
switch. Depress foot control.
Check as above.
Repair or replace
coolant switch. See
foot control section for
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