7i77 output issue

I've managed to get my 5i25/7i77 combination talking to the linear encoders on my mill - I get accurate readings on them, entirely in agreement with a DTI. I'm currently having a go at configuration with my old Anilam analogue drives so I can learn how to configure LinuxCNC without damaging new components (I've managed to burn out one old drive already).

However, I'm having problems with the analogue outputs:

As far as I can tell from the manual the analogue outputs are on TB5, with the first two pins being enable, the third pin ground and the fourth being the +-10v signal. Also from the manual it says that all of these outputs are tied down to 0v unless ordered otherwise commanded.

But - when I power up the 7i77, even with the DB25 cable unplugged, I find a voltage of 4v between TB5 pins 3&4 (GND & AOUT0) and also between 11&12 (GND & AOUT2), but no voltage difference between 7&8 (GND & AOUT1).

I've double checked this by connecting GND and AOUT2 to the X axis drive and, sure enough the X axis takes off fairly rapidly. Connecting GND & AOUT1 doesn't generate movement though.

I've currently connected the TB1 & TB2 connectors to the appropriate outputs (5v & 12v) from the PC PSU, but will be using separate power supplies once they arrive.

I have noticed that there is a red LED on the 7i77 near the lower right hand corner - does this indicate an error? I know there are red/green LEDs on the 5i25 to indicate status.

I thought I was really getting somewhere when I got the encoders reading correctly but now I'm confused... I'll attach a photo or two of the current connections shortly.

If you have 4V analog outputs on a 7I77 without commanding 4V outputs,
the 7I77 is failed or damaged and you should request a RMA from Mesa

Ok, thanks PCW.

That's a pain - I was hoping it was some small configuration issue on my part. I'll contact them tomorrow to sort an RMA.

Maybe this is the point where I bite the bullet and order some new PWM drives and a 7I85S rather than messing around with the old drives and the 7i77. In your opinion does that sound like a better bet than using both the 7i77 and the 7i76 (with the custom firmware you made up recently for me) to control PWM drives such as the Pico Systems ones?

Ben

We received your 7I77 and found that it was fine

What we suspect is that you were using the second encoder terminal block (TB4)
as the analog out connector instead of TB5.

if you measure the voltages on TB4 you will get your combination of 4 and 0 volts

Good grief - how did I not spot that??!

That's a massive PITA, not to mention highly embarrassing. In future I'm going to have to sleep on it, leave it for a week, then read the manual again before double checking!

At least I didn't break anything I suppose.

No, it was re-tested and we updated the firmware as well

Ah well, jolly good. My blood has stopped boiling now.

Thanks for the rapid turnaround on the testing and updating me so quickly.

Ben