Stepper drivers and power supply for Orac

[lsteele]

Hi,

I've recently obtained an Orac which I'm intending to refit with new electronics. It has two CD20s, but I'm pretty sure one is shot (smoke came off it when I powered it up), so I figure I'll fit new stepper drivers. The VFD is working, and I'm assuming the power supply is in good shape, but I'm not sure about the two big electrolytics on it.

So anyway, I have a couple of questions:

1) I'm wondering about using two PICSteps for drivers, the rationale being that I can make them fairly cheaply and they handle the highest voltage of any open source design I've seen (55V). That said I've read the Orac's steppers run at 70V, so I'll be losing a bit of power. Does anyone know of an open source design that supports the full 70V? I've seen lots of guys using Geckos but cost rules this out for me as I'm on a tight budget.

2) The power supply has laminated and toroidal transformers - can anyone tell me what these are putting out? Is there anyway I can get the 50-55V I need (assuming I go for the PICSteps), or do I need to build a new power supply?

3) With a view to preserving the Parametrics VFD as long as possible I was wondering about re-capping any eletrolytics on it - any comments? Also same goes for the two huge electrolytics on the power supply.

Thanks - any suggestion are gratefully received.

-Luke

[angel-tech]

the orac psu runs at around 60-65v, a simple replacement transformer will give you a lower voltage or invest in two 80v drivers.
I would leave the vfd alone as they tend to fail if you mess them about.
The toroidial transformer is the power for the drives and the smaller open frame transformer runs the logic.
Replacing the drives will give you an easier 5v interface for mach as the original cd20s use 12v logic.

[lsteele]

Ok, thanks. Should I replace the large electrolytics on the power supply?

Also what voltage does the open frame transformer put out?

[angel-tech]

i expect it will be 12-0-12vac 0r 24vac, and it may have a 110vac tap.

I've never replaced them, or heard of them being replaced.