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Oh Blimey I bought a CNC Lathe !!!!
awemawson:
OK NOW I'm confused :scratch: :scratch: but in quite a good way :clap:
It seems that the transformer I removed, previously, one coil of which is definitely driven by the FET off the rectified mains, also drives the other two transformers on the board, EACH of which provide four isolated + & - supplies. The first transformer also has one winding giving the 5v supply, another giving about 25 - 0 - 25 which goes to two 'conventional' series regulators, a 7815 (+15v) and a 7915 (-15v) both of which I had removed as at least the -15v one had blown up due to a blown capacitor on it's output. Tonight I decided to load the 5v supply with a 0.5 amp load, expecting it to drop like a stone. Not a bit of it - rock steady at 5v bang on to the nearest 10mV. This lead me to replace the 7815 (as I had one in stock), but to my surprise it only gave 7.8v unloaded, meanwhile the 5v supply was motoring along getting my load across it nice and warm !
So a few tentative conclusions:
A/ The DK-466 may not be faulty after all
B/ Either something down stream of the 7815 is heavily loading it, or there is something odd about the rectification from the transformer on this winding. Tomorrow I'll pull the 7815 out again (lucky I have a drawer full of them!) and load it's input independent of it's output circuitry and see what's amiss.
anyway it's sort of progress
mattinker:
It would seem you know something about electronics!
Best of luck, keep on doing the incantations and you should get the magic white smoke in the right places!
Regards, Matthew
vtsteam:
Yes, haven't commented in a bit, but best wishes, still following right along. :beer:
Fred Bloggs:
Andrew
Just another thought but does the machine have any more of the same pcbs on the other axises, if yes why dont you set another one up on the bench and have a careful probe around with the scope to get an idea of how its working. :med:
Best Regards
Fred
awemawson:
Fred: yes it does, and that's a good idea, though it's an absolute pig to remove it.
OK results of a bit more poking around: Firstly see the very simple circuit I'm working with:
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