The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
Thanks Pete, I'll wait with bated breath :thumbup:
awemawson:
I spent a bit of time this morning studying the KTK-Mentor DC Spindle Drive power board to see how feasible it is to replace those dodgy capacitors, and indeed try and determine what they are through the 'stuff' they have exuded.
The capacitors turn out to be PME261JC6100KR30 by Rifa and are 0.1 uf at 1000v DC / 500v AC - available in stock from RS but at quite a price. By Googling I discovered a place called Mercateo that I've not come across before that were noticeably cheaper - order placed.
So looking at the power board for the drive it is pretty daunting with loads of connections all waiting to trip me up, however sitting down and studying pictures of it, and working out which bit did what in fact it doesn't look to be too bad (famous last words!)
I took one of my pictures and annotated it to get things a bit clearer in my mind.
awemawson:
It turns out that this lathe was at one time equipped with two probing systems. As well as the tool probe which is hard wired, there has been a Renishaw LT02 optically coupled work probe that sits in a pocket in the tool turret and can measure a work piece.
The Optical Receiver and interface unit are still in place, and amongst the scanty documentation is the installation manual and test certificate BUT NOT THE PROBE.
. . . no, not the probe 'cos the chap who I got the other probe from flogged it on eBay back in April :bang: :bang:
(amazing what a bit of data mining reveals!)
Come on empty your pockets - who's got a Renishaw LT02 probe for me
AdeV:
You've already found what the cap is... but I was going to suggest it looks a LOT like an AC smoothing capacitor. Sharp fitted them (or one very like them) to all of their 1980s computers... and these days, most of those computers (often having spent years in cupboards and attics) usually blow them fairly soon after being plugged in. As a side note, somewhat oddly, they're connected directly to the mains before the switch.... so an old Sharp can give a scary-sounding :zap: BANG and a cloud of magic electrical smoke even when it's turned off!
Chances are, that cap is entirely surplus to requirements, and it's rather sorry state is due to the fact it's already gone bang & let out the magic smoke.
Still... better in than out (as no-one ever said). :nrocks:
awemawson:
Reading up on RFI suppressor capacitors it's actually an interesting and more complex situation than you might imagine.
OK we are trying to suppress RF noise and the capacitor does that, but it has to be able to stand up to the environment in which it finds itself. All mains systems suffer from voltage spikes. Either back EMF from other devices or noise on the transmission lines caused by network switching or lightening for instance.
The chosen capacitor needs to withstand these spikes, but the fact is that actually they don't. There is usually a breakdown of the insulation that vaporises a tiny bit of the metalisation that forms the plates. Insurance rated capacitors like these ones have to have self extinguishing insulation and a 'self healing' characteristic whereby the capacitor continues to function but at a slightly reduced capacitance. Apparently on average equipment sees 18 of these spikes every day :bugeye:
A bit about it here:
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version