Chester Conquest lathe just gone ‘pop’ !

[AndyfParticipant @andyf]

Your link seems to go through to a KB electronics manual, Steve.

The S8010L SCRs are available from Farnell (order code 1869397), though it might not be a bad idea to use S8020Ls (order code1869399) instead; they are rated 20A rather than 10A.

Farnell also do a D8020L diode, again 20A (part no 1456539). I couldn't find a D8010L 10A one.

The 80 seems to indicate 800V, and the 10 or 20 the amps rating.

All made by Littelfuse, as you say.

Andy

[nigel jones 5Participant @nigeljones5]

Ive had the equivalent lathe and mill go pop! No one could fix it. I ended up putting a big drill motor on the lathe and a big diode on the mill to get it to run. I now run the mill on 115v if I want it slow. Actually worked out rather well but I sure wouldnt buy another!

[Steve WithnellParticipant @stevewithnell34426]

Posted by Steve Withnell on 18/08/2012 19:08:56:

Posted by Les Jones 1 on 18/08/2012 09:19:05:

Hi Steve,
Without a schematic of the board do not think it is possible to diagnose the fault. The only thing I can say is that I do not think it is a fault in the power control devices (SCR's Triac, Mosfets etc.) as these tend to fail to a shorted condition which would mean that the motor either ran at full speed all the time or the fuses blew. If you trace out the schematic of the board I will try to work out what may be causing these symptoms.

Les.

Thanks for the kind offer Les, but I doubt I'll be able to trace out the board. He did say when he subsequently tried to use it it did go to full speed and could not be controlled. Dad (82) isn't in a rush (he has his Grandad's Brittania set up for rush jobs…) so I'll try and get hold of the schematic and see if I can find the board on Google to give me a clue.

I'll let you know what I find.

Turns out the controller is a KB Electornics 240 controller with 8010 series devices. I can't find anythinf amiss with the discrete semiconductors on the PCB whilst in circuit.

Yesterday I did some continuity checks between the field windings, armature windings and the frame, and didn''t spot anything amiss there either.

What I'd like to do is bench test the PCB – what loads should I use for the Armature and Field outputs? I saw somewhere that light bulbs where a useful load.

Any thoughts?

Steve

[John RuddParticipant @johnrudd16576]

The board can be bench tested radily using a 100watt light bulb connected to the A+ and A- connections. The field winding is just energised with rectified ac…

Connect your AC supply to the board via another 100 wat light bulb ( adds a degree of protection against blowing scr's and the like), connec the other 'load' to the A connections as above and add a pot to the P1,2, and 3 connections..Varying the pot should vary the intensity of the load bulb…..If you ned further help then pm me, I also do a repair service/exchange scheme for these boards…

[Steve WithnellParticipant @stevewithnell34426]

Thanks John. Service/exchange might be welcome. I'll wire it up and let you know!

Steve

[Martin Brown 4Participant @martinbrown4]

Hi,

I am after the speed control pot for a Chester Conquest Lathe. Anyone have any ideas as to where I could get one? Does it have to be the original part, or could I just get a 4k7 pot with on/off switch? Not sure of the powere rating of the pot. Thanks

Martin

[Author]

Posts