Herbert 4 Senior Pre-Optive Lathe Problem

After being in storage for about 10 years I have relocated an old Herbert 4 Senior Lathe to a new workshop. I was working previously via a 3 phase converter but it did work OK. It was sprayed with oil prior to storage and it all looks in quite good knick.
When I powered it all up I could not get the pre-optive motor to operate for a while. I found 3 small 5 amp fuses, some of which had blown, - not violently, just not connected and a few other problems. The pre-op motor would turn, using a small socket and extension but only about 20 turns from one jammed position to the other. Also the main speed knob was jammed. I also turned the main motor which was free and which turned the chuck - so it was all free and in gear, highest speed was selected. I finally got the pre-op. motor driving and going the right way but it still jammed after about 20 revs from the fully anti clockwise jammed position. After messing about for about an hour, running from fully anti-clock to fully clock, it suddenly overcame the jam and the speed knob freed up.
Aha! I thought, now it will be OK. But no, even with the pre-op. motor running and the speed selector apparently free, the main motor would not come on. Previously there was a big click of the power relay(s) when you pushed the forward, reverse or inch buttons. Then the pre-op. trip tripped again (as it always used to if left running for a while due to the converter not giving true 3 phase), when I reset it the jamming was there again.
Does anyone know enough about this old Lathe to suggest what may be wrong and does anyone have either a circuit diagram or handbook (or both) that I could beg borrow or buy. I am sure there is not much wrong with it and I really don't like to attempt the dismantling of it to get into the pre-optive gearbox assembly.
Any comments or suggestions would be welcome. It is a fine machine and I am sure I can put it to good use again.
Thanks a lot, George Bell.
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George wrote:

try asking on uk.rec.models.engineering
Dave
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