Time Electronics 1010 DC Voltage Calibrator - Manual (Page 7)

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1010 Technical Manual 7
2.7. Mains Power Unit
2.7.1. Type PU2
The PU2 incorporates a rechargeable Nickel-Cadmium battery and electronics charge
control circuitry. The circuitry is arranged to enable the PU2 to provide power directly from
the mains if the mains input is connected or alternatively from the rechargeable battery if
mains is not connected.
When the mains is connected the charging circuitry provides the correct charge current (40-
45mA) for the battery and automatically reduces this to a trickle rate (3 - 4mA) when the
battery is fully charged. This means that it is impossible to overcharge the battery.
The DC performance is as follows:
With mains connected: DC output 15.5 - 7V (0 - 100mA load).
With mains disconnected (and battery fully charged): DC 14.5 - 15.5V (0 - 100mA load)
Mains input range: 110 - 250V AC 40 - 60 Hz. IEC mains input fuse is 20mm F1A.
The capacity of the rechargeable battery is approximately 450mA Hrs. This allows about
40 - 50 hrs continuous use of the 1010. To fully recharge the battery requires 14-16 hours
with mains connected.
2.7.2. Constructional details PU2
The P.C.B. is located on the rear panel by 4 screws and is spaced off approx. 10mm. A
metal cover protects and screens the P.C.B. and components. The output connectors and
output fuse are located outside the cover. The cover is fixed to the rear panel by a 4 screws.
Later versions of PU2 have a 20mm F500mA fuse located inside cover.
Important Note: Take care when checking and dismantling a PU2. Even though
disconnected from the mains, there is still sufficient power stored in the rechargeable
battery to cause catastrophic damage to the electronic circuitry if inadvertent short
circuits occur. These can easily occur when the metal cover is being removed.
2.7.3. 240V to 110V conversion
The PU2 mains transformer has tappings for 240V or 110V AC mains. The following
procedure should be adopted to convert from 240V to 110V.
1) Remove mains power unit from 1010.
2) Remove P.C.B. metal screening cover.
Note: Take care not to short any part of the circuitry when converting a PU2.
3) Connect mains transformer windings in parallel by rewiring the mains input to the
transformer (As shown on the side of the transformer).
4) Replace the screening cover.