User Guide
Landcal Blackbody Source
Type R1500T
Page 15
8.4 Replacing solid state relays
1) Disconnect the furnace from the electrical supply.
2) Remove the lower side panel (not containing controller) from the furnace.
Locate the solid state relay(s), removing any other panels necessary to
give reasonable access.
3) Disconnect the ve wires, noting their numbers and positions.
4) Remove the faulty relay and replace it with a new one, noting which way
round to t it.
Original relays are tted with a thin layer of ‘off-white’ paste to give good
heat transfer to the aluminium sheet. New relays are supplied with a
heatsink 'pad'. All remnants of the old heatsink paste must be removed.
The thin white heatsink pad must be tted between the solid state relay
and the plate to which it is mounted.
5) Tighten the two xing screws.
6) Ret the wires as noted in step (iii). If the replacement solid state relay is
supplied with a metal oxide varistor (MOV) it must be connected between
the load terminals as shown in Fig. 6. It is not polarity dependent. The
MOV protects the SSR from short periods of excess voltage. If the
replacement SSR is supplied without an MOV this is because later versions
have the MOV built in.
7) Replace the panel(s).
8) Reconnect the furnace to the electrical supply.
Load terminals (2)
Logic signal terminals (2)
Solid state relay
MOV (if fitted)
Fig. 6 Connections to solid state relays
CA970252
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