[torinwalker]

The CHNC is wired so that each control signal has a common ground (always terminal 3), with terminal 4 wired back to the interface board and on to the control where I presume a smaller transistor switches on a 24V buss.

Terminal 1, the AC output is typically tied to a 110V buss, with terminal 2 going back to whatever it's driving.

I first check if terminal 4 has 24 volts on it. If the control terminal is at zero volts (logical zero), then terminal two should have zero (or very near zero - I was reading 3 ~ 4V) on it... whatever - probably high impedance noise, but close enough to zero volts. If the terminal 4 (control) is positive (logical one), then terminal 2 should also show 110V.

So in the case of the Vertical Slide Motor relay, even though the control showed zero volts, both terminals showed 110V, meaning the relay was shorting terminals 1 and 2 despite not having the logic to drive it that way.

Other terminals, 1 through 9 show the correct logic. When the control is at zero, the common terminal 1 is high, and terminal 2 is at zero. Likewise, when the control is logically high (at 24VDC), both 1 and 2 are at 110V.

The unused relays still had terminal 1 tied to the 110V buss, so even though they're not used, terminal #2 (not attached to anything) should still show 110V when the logic is high. In this case however, the unused relays had zero volts from control, yet both 1 & 2 terminals showed 110V.

Just now I looked up leakage for SSRs and one brand in particular shows leakage on the order of 1/1000 (140ma @ 140V), so I might have been reading the 3~4V correctly, but I doubt the outputs of unloaded SSRs would float at 110V with their controls off. That makes no sense, and it contradicts what I read between relays I knew worked, and ones that I knew didn't.

BTW, I did these measurements with the control off so I could validate 110V at #1 with zero at #2 for known-working relays, relative to those (relays #10 and #11) which showed 110V at both terminals even with control at logical zero. So I'm pretty sure I measured them correctly. Still, I'm open to opinions.


Torin...

[Al_The_Man]

What throws many is that with a very sensitive meter, it is possible to read 120vac on both sides of an SCR output when it is actually off and no load connected due to leakage current which gives the impression it is conducting, but in fact it would not support any current when a load is connected in this condition.
Al.

[torinwalker]

For all the ones that were live, I diagnosed them correctly. Fortunately, the ones that weren't connected to anything, they were still working which means I was able to swap two good ones (taken out and tested with a light bulb and a 9V batter, btw) with the two that were faulty (also confirmed with the bulb/battery.)

So now, when my machine is powered on, the hydraulic motor is off - as it should be. When the control comes on, it still stays off.

But now I have a new problem - the vertical slide works in REVERSE! When I issue an M25 (retract chute/vertical slide), the slide extends in. When I issue an M23, the slide retracts. Go figure.

The other problem now is that when the M25 is issued (which should retract the slide, but instead extends it), the hydraulic motor squeals against the high pressure bypass and still depletes my air compressor in a matter of under a minute.

Now I have to figure out why the slide is working in reverse. I figure it has to do with the direction valve being configured backward somehow, but I'm running a job on the milling machine and can't have the compressor down. I'll have to look at this later. At least I know the relays are working correctly because the motor turns on and off on demand now, and I can command it in a particular direction, even if the direction is wrong.

The 4-way directional valve is powered by a 110V signal and consists of A and B ports, with (supposedly) the default (un-engerized) state being configured to retract the vertical slide. Perhaps the hydraulic lines were installed in reverse.


Torin...

[Al_The_Man]

Either the Lines or the opposing coils are energized incorrectly, maybe?
Al.

[night owl]

I've had to replace quite a few SSR's on older Mazaks (soldered on the PCB) because they didn't provide any overload protection. I guess they just figured that a SSR is it's own fuse?

[torinwalker]

I did it.

I finally fixed her up. After finding some documentation on the Parker directional valve, it was clear that the solenoid could only move in one direction, and the port blocks all appeared to be correctly orientated, so I started tracing the hydraulic lines throughout and as I suspected, the A port was connected to the extension side of the piston rather than at the retraction side. In retrospect, it is now more obvious. By looking at the hoses in the valve compartment, one can see that of the hoses was a stretched tight all the way from the left where it enters from a bulkhead to the right on the tank return, while the other was much longer and looked like it had been tucked away, pressed against the roof of the cabinet. When I reversed the hoses, they sat more comfortably, and of course, the vertical slide extended when I issued an M23, and retracted with an M25!

Yay. So, I sat there for a while - Slide goes in. Slide goes out. Slide goes in. Slide goes out. :-)

One last slight adjustment remains that I'll probably tackle another day - the adjustment knobs (valves) on the vertical slide don't appear to have any effect on the feed rate of the slide - it travels inward and outward a little too fast for comfort. Opposing the slide's movement with my hand didn't appear to slow it down either (I was checking if the system needed bleeding of air.)

Do you think air might have an effect on how fast it traverses (i.e. faster than normal?)

Well, this has been fun. Thank you everyone for your interest, and to Al, who pointed out that there is indeed a right way to test unloaded SSRs.

If anyone is interested, Crydom (the mfg of SSRs I was testing) has an informative document about testing SSRs: How to test an AC Solid State Relay


Now I need to fire up another thread about what the vertical slide should look like (how fast should it move) when being tested on air, versus cutting into metal.


Torin...

[night owl]

I'm not familiar with your machine, but you might consider throttling the air to that pump motor to slow it down some.

[torinwalker]

Sorry, that was the wrong link. This is the one I was thinking about:

How to Bench-Test a Solid State Relay


Torin...

[torinwalker]

Night Owl,

Not a bad idea, but I get a lot of "low pressure" alarms when the pressure drops below 80psi. I'll keep it in mind if I have no other alternative.

The vertical slide has two adjustments - one at the base for controlling the overall feed rate, and a second at the top that is supposed to define when the slide transitions from rapid to fine-feed.

The valve at the bottom feels quite loose while turning it outward, but as soon as the slide activates, I can feel a little thwack of the valve butting up against the screw. I'd rather not have to take it apart.

I think I'll try bleeding the system first, and see what happens. I'll update this thread later when I have a chance.


Torin...

[torinwalker]

I'd like to pose one last question, if I may, to those who may still be listening (and who have CHNC1's with the cut-off attachment): What is your observation of the cut-off slide movement without having material in the lathe? Does the speed change when the valve is activated? Or, does it only change speed when the cut-off slide (tool) is actively loaded (cutting material)?

Torin...
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