Metrohm Autolab
Service Document # 003
Wrong resistance on control amplifier PCB triggers irregular behavior in current
measurement when instrument is warm
For PGSTAT12, PGSTAT30 and PGSTAT100 (7 series)
Symptoms: the symptoms for this problem are a possible failure of the current
measurement in a TestCV when the instrument is warm. This issue will also be
detectable as a Potentiostat and Galvanostat test failure in the Diagnostics
application. Letting the instrument cool down will usually correct the problem.
Description: modification of the control amplifier of the PGSTAT for correction of
current-interrupt related problems on 7 series PGSTATs. Some of the instruments in
this group are fitted with the wrong resistor on the control amplifier. The problem
can be addressed by removing the resistance from the control amplifier PCB. This
document describes the steps to take in order to correct this problem.
Recommended service action: Metrohm Autolab advises to systematically check all
instruments received for service for this issue.
Note: the PGSTAT128N, 302N, 101 and the µAutolab II and III are not affected by
this problem.
Component identification and location:
R21 on Control Amplifier PCB of PGSTAT12
R31 on Control Amplifier PCB of PGSTAT30 and PGSTAT100
The following components are involved in the problem described in this document.
PGSTAT12
PGSTAT30/100
Wrong resistor R21:100 kOhm, proper resistor R21:220 kOhm
Wrong resistor R31:100 kOhm, proper resistor R31:220 kOhm
Autolab Service Document # 003 – Modification of the current interrupt circuit
If a 100 KOhm (see Figure 1) resistor is mounted located on the Control Amplifier
PCB, remove it from the PCB, without replacing it with a new resistor. This resistor
can be accessed without removing the control amplifier PCB. To reach the resistor,
removal of the Autolab casing is sufficient.
Figure 1 – The wrong 100 kOhm resistor (top) and the correct 220 kOhm resistor (bottom) are
easy to identify by their respective color codes
For the PGSTAT12
The position of the resistors on the Control Amplifier PCB is shown in Figure 2.
Figure 2 – R21 is located at the bottom of the Control Amplifier PCB
If the wrong resistor is located on the PCB, simply remove the resistor by cutting the
wires (see Figure 3).
Autolab Service Document # 003 – Modification of the current interrupt circuit
Figure 3 – Cut out the resistor from the PCB if the value is 100 kOhm
PGSTAT30:
The position of the resistors on the Control Amplifier PCB is shown in Figure 4.
Figure 4 – R31 is located in the middle of the Control Amplifier PCB
If the wrong resistor is located on the PCB, simply remove the resistor by cutting the
wires (see Figure 5).
Autolab Service Document # 003 – Modification of the current interrupt circuit
Figure 5 – Cut out the resistor from the PCB if the value is 100 kOhm
PGSTAT100:
The position of the resistors on the Control Amplifier PCB is shown in Figure 6.
Figure 6 – R31 is located in the middle of the Control Amplifier PCB
If the wrong resistor is located on the PCB, simply remove the resistor by cutting the
wires (see Figure 7).
Autolab Service Document # 003 – Modification of the current interrupt circuit
Figure 7 – Cut out the resistor from the PCB if the value is 100 kOhm
Final verification: allow the instrument to warm up and run the procedure TestCV on
the Autolab dummy cell. Set the number of scans to 1000 before starting the
procedure.
Autolab Service Document # 003 – Modification of the current interrupt circuit