Fobco 10 eight drill, NVR problem

[dareay42Participant @dareay42]

I’m trying to assist a friend who has acquired the above drill. Mechanically, all is well, however there is a problem in that the ‘no volt release relay’ doesn’t always release. I was an electrician in a former life, and I’m happy with the wiring, which looks to have been replaced at some time. The machine appears to have the original Crabtree Stop & Start buttons which are operating cleanly, but the T6 relay itself does not always drop out immediately, pausing for a second if switched on and off almost immediately, or up to 2 or 3 seconds if it’s been running longer. My friend mentions he’s had one or two ‘brown trouser’ moments using the drill !

The relay is mounted on a steel back plate which looks to be a replacement for whatever was there originally. I wonder if this was originally an ‘insulating’ material, and the present steel back plate is ‘slugging’ the relay coil.(Not yet tried it separated from the back plate.)

Does anyone have any views on this?

David

[Robert Atkinson 2Participant @robertatkinson2]

I think you are correct in thinking the back plate is the cause. Either that or the core / armature has become permanently magnetised or a armature spacer (if fitted) has fallen off or worn away.

Robert.

[dareay42Participant @dareay42]

Thanks Robert. The armature seems to be free moving, and there’s no reluctance to it clunking in, just the very slow release. One of the very few references I’ve seen to the T6 relay on’t t’interweb shows where a relay is apparently remote mounted in a metal case. The inside of the case shows raised mounting lugs, indicating an air gap under the relay. I’ll be trying ‘ours’, minus it’s metal plate when I get back to my friends workshop.

David.

[noel shelleyParticipant @noelshelley55608]

While the magnetic issue seems a possibility is a capacitor discharging through the relay coil ? Noel.

[dareay42Participant @dareay42]

I thought of that Noel, back feeding from the motor capacitors, but we’ve tried it with the motor isolated, just a test lamp on the switched contacts; same result.

David.

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