> 
> Nope, never fly.  See if superglueing some heat sinks to them might help, 
>and 
> in my case, I have a pair of old psu fans running on about 18 volts to they 
> really sing to you, one in each end of a box with the xylotex board in it, 
> the box just fitting the outside dimensions of the fans, one blowing in one 
> one end of the box, the other sucking out the other end, so I probably have 
>a 
> 20 mph breeze flowing across both sides of the pcb itself. I've had one fan 
> fail in about 5 years, so if you start with decent computer psu pulls that 
> claim to be ball bearing models, and it lasts 10 minutes at the higher 
> voltage, it should last 5-10 years.  I used 18 volts basically because that 
> was the only lower tap I had on the motor psu I built from an old Ampex 2" 
> videotape machine's drum motor power supply.  Its a boat anchor if it ever 
> fails...
> 
> Watch the electrolytic caps, the things in alu cans with plastic wrappers 
>but 
> bare tops.  If you see even a hint of bulging of the top of one of those, 
> replace them last week if not before.  I haven't read any horror stories 
> about those, yet.  But I am a retired C.E.T. and have been seeing problems 
> with those ever since switching power supplies, with their light weight and 
> high efficiencies causing a wholesale shift to their use for nearly 
> everything.
> 
> Switching power supplies however are _not_ good power supplies for this use, 
> they cannot absorb the energy recycling currents that flow in these chopper 
> stabilized drives without either letting the output voltages soar out of 
> spec, or seeing it as an error and doing a protective shutdown, usually in 
> the middle of the most intricate cut of the job.  Been there, done that, 
> built the linear, unregulated but huge output capacitance (75,000 uf, it was 
> handy in my junk box) rig I now use in self defense.  It hasn't even gotten 
> warm in 5 years of running 4 motors on my mill, sometimes for several days 
> straight.
> 
> In any event, I don't think I would, even with heat sinks and fans, push 
> those at above 2.0 amps/motor.  That limit will only effect, generally 
> speaking, the amount of force available at slow speeds.  Only more voltage 
> can get you above something like 20" a minute, and that will probably need 
> dampers on the motors to achieve that.  I'm at about 27.5, so I can go a wee 
> bit faster than the std 24 volt supply will get you to.  30 is pushing the 
> envelope and may let the smoke out of these chips.  I run at 2.5 amps, but 
> you could say I have extreme cooling too.
> 
>For motor dampers, there are several designs extant.  Mine are big fender 
> washers with sheet rubber between them in loose stacks, others have used 
> weighted skate wheels and such effectively too.  You can see mine, and I'm 
> sure others here will also give links to their designs, on the back ends of 
> the motors you can see in my mess at 
><http://gene.homelinux.net:85/gene/emc>, 
> that bypasses the front page but only shows you filenames, click to see in 
> most browsers.  Or you can take off the 'emc' and see me & the missus and 
> some smaller web sized pix.
> 
> Good luck. ;)
> 
> -- 
> Cheers, Gene
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> 
> Some one needed the powerstrip, so they pulled the switch plug.
> 
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Hi Gene:

Thanks for the insight.

yes I don't trust switchers. I am a ham radio opt. and so I build power 
supplies with xformers and the like.

I took a look at some of your pictures and was woundering what size your 
steppers are???

I know one of my problems are small steppers.  I was going to buy larger ones 
but haven't yet.  As I said before I want to be sure that the machine goes to 
the position it is sent to,  but I could get a great deal of money spent by 
starting all over using servos.

I also am retired and money is tight for hobby stuff.

By the way, your shop looks great...

Bill

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