DISPENSERS
Problems with dosing accuracy are most often due to tubing.
Mechanical
problems, due to ageing of components, are summarised under their model numbers:
ACCURAMATIC Mk7
Our current model,
which came onto the market in 1999. It has no known problems, and all spares are
stocked.
ACCURAMATIC Mk6
Microprocessor
controlled version of the Mk5, based on Arizona Microchip's PIC16C54(/A).
Deleting many electromechanical components improved longevity and simplified the
user interface. Some software changes during production.
In service
problems: occasional processor latch-up: the processor retains data by going
into 'sleep' mode on power down. Occasionally the processor crashes and is not
reset on power up. Typically, this shows as a 'garbage' screen output, but may
also manifest as other bizarre activity, eg motor run on power-up, permanent
'auto' state etc. Reset by discharging back-up battery (disc shaped 1F device on
lower corner of pcb: has internal resistance, so not damaged by short circuit).
Later models have a reset button on side panel - operate reset with power
OFF.
Spares - all held or obtainable
ACCURAMATIC Mk5
The first model in
which the pump did not run continuously. In 10 years of production it underwent
some design changes. The first examples had a counter at the top of the front
panel and no interface socket: they were built in a standard 'Elf' case. Pump
rotation was controlled by a changeover push switch (prone to damage) on the
left side panel. Later models had no counter, had soft-stop and direction rocker
switches on the side panel, plus the interface socket, and were housed in an
aluminium and steel case. Later still, the printed aluminium front panel was
replaced by a cnc-engraved plastic laminate.
In service issues
include:
FRONT PANEL COMPATIBILITY: about midway through production, the
McMurdo 8 way connector used to connect the front panel ceased production and
was replaced with a standard 9 way D connector, making older model panels
incompatible with newer machines and vice versa. An old type connector can be
easily replaced with a D, but TAKE CARE - this connector handles mains voltages.
The McMurdo connector has only rather small splines to prevent incorrect
insertion. Make sure wiring colours tally - incorrect polarity will cause a lot
of damage!
MOTOR DRIVE TRIAC: on the front panel pcb is NOT isolated tag
type. If you run the machine with front panel detached for diagnostic purposes,
beware of this source of electric shocks!
MAIN IN-SERVICE PROBLEMS: loss of
accuracy caused by breakdown of 10- turn potentiometer. Mechanical failure of 10
turn counter. (Both these just the result of mechanical wear). Motor brake can
eventually fail due to mechanical wear - early brakes seem better than later.
Switches may be broken or damaged by moisture/product spillage. Late plastic
front panels and all mains inlet sockets may be damaged by solvents, usually as
deplasticization, embrittling them. Motor run capacitor occasionally packs up
due to age - characterised by the motor failing to run or running slowly: if
flicked round it will run either way. (Not to be confused with motor failing
to run because direction rocker switch is lodged in mid position).
Transit/drop damage: if the machine is shipped without adequate packing or
roughly handled, the left hand side panel is belled /bent by the weight of the
motor.
Spares: all held or obtainable
ACCURAMATIC Mk4
Nothing to do with
us! Electromatic built some machines for Jencons Scientific with this
designation. Contact either for information.
ACCURAMATIC Mk3 and DUOSPEED
The
whole production was sold through Jencons Scientific, whose name appears on the
front panel. Hundreds were built and many remain in service. They represented a
quantum leap, technically, above the F3: the electronics are on a printed
circuit board! During production, the whole design went through myriad upgrades,
culminating in the DUOSPEED, which had two pumping speeds. The shifting design
makes it difficult to highlight typical problems, but a few may be picked
out:
OFF/SLOW/FAST SWITCH The slow operation of this rotary switch leads to
its early demise. Very frequently replaced by 3 pole double throw toggle switch
(C&K 7303 SYZQE or equivalent) as a retromod.
DOSE START SYNCH In order
to start the dose at a consistent point on the pump rotation, a pair of
motor-car ignition points and operating cam are mounted on the pump drive shaft.
These may cause problems due to wear, or the operator may find that a very brief
press doesn't start a dose - not actually a fault, just a characteristic of the
type.
MOTOR/PUMP COUPLING A variety of couplings were used in production. The
Oldham type is the one we usually use as a replacement - it's still available!
RS stock number 748-099 (one end bored to 10mm).
Spares carried: Pumpheads,
gates, thumbnuts, a fair number of pcbs and front panels of some (but not all)
patterns. Various solenoids. NO motors: talk to Parvalux, who may be able to
help. No T-pieces for tubing sets - these were supplied by the distributor, not
by us.
ACCURAMATIC F3
Examples are
approaching 30 years old, few are still in service. Wear and tear may,
understandably, be considerable. Other typical problems include:
1.
Accumulated dirt stopping the solenoids from closing fully, so the gates don't
seal off the tubing completely. Sometimes operators wound tape round the gate to
make them more effective, but this is a self defeating strategy as the solenoid
develops its full force at maximum travel: padding the gates limits the travel,
reduces the force and therefore makes leaks more likely rather than less.
Removal of the solenoid plungers for cleaning is straightforward.
2.
Physical damage. The electronics (!) and solenoids are mounted on perspex bases
which tend to shatter if dropped. Replacement bases are better made from thin
tufnol or other laminate.
3. Timing is by SCRs, which are fairly prone to
latching. There are two timing units (one for dose timing, one for interval),
built into valve bases. They are identical and interchangeable, which aids
testing.
Spares carried: Pumpheads, gates, thumbnuts. Not very many
electrical parts, but because these machines were pretty simple, we've always
been able to effect repairs. Engineers working on these machines are invited to
contact Accuramatic for support and information as required: if we can help, we
will.