TLHarrell wrote:Any chance you can walk me through some testing methods to confirm/deny the power supply issue? I've never used a scope, and I'm not sure what I'd actually be looking for. (That, and I'd hate to blow up a friend's scope by hooking it up wrong.)
Hi
(I couldn't get your name from your sig
)
There would be no problem walking you through it if I was sitting on your shoulder - doing it over the net is a different matter altogether
All scopes are not equal, controls are different and some of the more up to date units require a first degree in astro physics to drive them
Also, as you say, you wouldn't want to blow up his scope (unlikely though that is
).
Here's what I would suggest, if you can get a scope from a friend, bring him or her along to drive it.
First check each PSU for the correct voltage with a DVM (on load - make sure everything is on) - the voltage should be within about 0.2-0.3V of the nominal PSU voltage. If any are well off the mark, that may be your problem.
Hook up your scope to each PSU rail in turn - scope ground to system PSU ground and the probe tip to each positive rail in turn. Scope should be set to about 10mV/cm AC coupled - set trigger to auto for now - again make sure everything is on and loaded up. There may be some random system 'noise' which may involve fairly high spikes (in a perfect system, they wouldn't be there, but nothing's perfect). On 'old' analogue supplies, we would be looking for mains ripple (50Hz europe - 60Hz US) - but most modern el cheapo chinese PSUs are switch mode, so it will be a high frequency ripple instead - let's say about 20KHz for now. If this ripple is more than about 300 - 500mV, you may have a problem.
If you can't get a scope or a good set of replacement PSU's, you could temporarily swap out the supplies with batteries - don't use ordinary alkalines, I would suggest NiCd or NiMh - a high current model a/c Rx pack of about 2200mAH at 4.8V will hold the system 5V up for a while - a 12V Tx pack of the same will do your 12V - ditto a pair of Tx packs in series for the 24V - or even combinations of Rx packs. I don't know what your system consists of in the way of PSUs - I have 24V for the steppers and a separate isolated 12V with 5V and 3.3V derived from that . The good thing about using batteries is that they are noiseless and can show up other issues - odd things like 'artefacts' being printed - zig zags, rough edges and the like - all attributable to bad PSUs.
It's conceivable of course that the controller IS bad
Hope this helps.
Cheers
Neil