Abacus
4
Service Manual
55
B. Bad insulation of electronic signal paths:
In these cases check for any capacitive coupling of electronic signals to the chamber:
interference with HGB head
(high-frequency signal is coupled to the chamber). HGB head
metal parts must be grounded. The ground comes externally, it must be in place, otherwise
HGB head does not shield, but couples in noise.
interference with internal high voltage inverter
(high-frequency signal is coupled to
the chamber). Repair is required: avoid near contact of HVB cable to chamber or shielded
amplifier cable.
interference with internal start button
(polling signal to start button may cause noise).
Guide start button wires as far from chamber as possible. You may try mix them up on the
start micro-switch if applicable.
interference with display cable
(high-frequency LCD signal is coupled to the chamber by
the ribbon cable). Keep the ribbon cable far from the chamber.
interference with CPU fan or other digital logic traces
(CPU fan or other digital signal
radiates to chamber or to the shielded amplifier cable). Try keeping the ribbon cables far
from the chamber and shielded cable.
C. Bad components, or connections:
bad soldering, salt residuals or component failure on amplifier
(especially if some
reagent could get in the amplifier section). Cleaning of PCB/electrode socket or replacement
of amplifier is required. Check for the correct soldering of reference cable and its connector.
circuit board bad soldering or component failure
. Check the shielded cable connections
as well. Sometimes inside out connection (hot electrode goes outside as a shield) is the
problem: both ends of amplifier signal cable must be reversed.
analog signal ribbon cable
(it picks up noise). Check the ribbon cable between the circuit
board and the amplifier. Maybe it is pinched under some screws or components. This may
cause trouble and even noise.
D. Pneumatic failures, liquid paths that conduct noise into the chamber:
liquid remains under the chamber in drain tube
(during measurement the conducting
liquid remains inside the drain tube making noise to appear there).
Check chamber draining path for clogging or salt crystals.
Check the pump operation. Since draining of the chamber goes under pressure
control, maybe a bad pressure sensor or connection can cause trouble.
Clean the draining path. Do not use alcohol, but bleach. Replace chamber if
necessary.
liquid remains in the washing inlet at top of the chamber
(during measurement the
conducting liquid remains inside the chamber wash tube making noise to appear). The
software is not compatible with the mechanics, or related valve is bad/partly clogged, or the
tubing is clogged/loose.
lyse path guides in noise
(during counting, if the a liquid in the draining tube is touching
lyse reagent in T-fitting, noise can appear). Check the lyse path, and the lyse valve as well.
