Time Electronics 1024 DC Current Calibrator - Manual (Page 10)

10
1024 Technical Manual 10
3. Constructional Layout Details
The complete instrument assembly (except the Power Unit) is mounted on the front panel.
A printed circuit board which carries the components and range switch is located
immediately behind the front panel. The panel and p.c.b. can be removed as follows:
1) Remove Power Unit - located in instrument rear by 4 screws.
2) Disconnect supply - connected to power unit by 2 press stud connectors.
3) Remove front panel locating screws.
4) Withdraw front panel and p.c.b. - the power supply lead can also be withdrawn through a
hole in the plastic power supply cover.
For recalibration the power supply can be connected without rehousing in the case.
3.1. Chopper amplifier module
3.1.1. Description
The module contains the F.E.T. Chopper amplifier, precision zener and associated circuitry.
It is a fully encapsulated module and connections are via a 16 pin connector moulded into it.
The modular form of the 1010’s basic circuitry protects it from damage due to adverse
conditions and thermal gradients which could give rise to thermal emf errors. A replacement
procedure should be adopted in the case of failure or malfunctioning of the module - see
Section 3.1.2.
3.1.2. Module replacement
1) Remove and disconnect power unit located in instrument rear by 4 screws.
2) Remove front locating screws.
3) Carefully withdraw the front panel and associated printed circuit board (p.c.b.). The power
supply lead can also be withdrawn through a hole in the plastic supply cover.
4) Remove 4 nuts which locate the module on the p.c.b.
5) Withdraw the module from the p.c.b.
6) Remove 4 nuts remaining on module mounting studs. Put these nuts on the new module.
Replace new module in reverse order ensuring the connector pins align correctly - it may
be necessary to bend slightly the mounting studs in order to obtain smooth alignment of
the 16 pin plug and socket.
Note: It is important not to overstress the plug and socket, since poor connection will result.
7) Adjust the position of the module above the p.c.b. with 6 nuts on the module side of the
p.c.b. When the module is parallel the plug and socket just closed, the nuts on the
opposite side of the p.c.b. can be tightened. It is important to ensure that no strain is put
on the connector when the nuts are finally tightened.
8) Set Module zero and recalibrate as described on the following page.