Mesa 7i48 problems - knackered 7i48?

Hi all.

I recently bought Bridgeport Series 2 Interact 2 and have inherited a mostly working system from the seller, but have run into problems getting the drives running.

Main card is 5i23 with 5i23_7i48_7i52 firmware. The 7i52 seems to only be there to provide a sserial port for a 7i84, which deals with most of the I/O.

I can’t get +/-10V out of the 7i48 card any more. A couple of days ago I had a small breadboard made up with resistors and LEDs to check for analogue out before hooking up the x-axis motor to test. That worked, so I connected the x-axis motor and could move it using the jog keys and was getting ready to start tuning. Returning to it yesterday, it seems to have died: can’t light LEDs, can’t jog the motor, no voltage showing across the relevant AOUT/GND screw terminals.

PWMGEN is set to type 2 (Up/Down).
+(-) and -(+) - the command inputs for the Bosch Z15 amp - are connected to AOUT0 and GND0 on the 7i48, with the command cable shield also connected to the -(+) line per the amp manual.

If I disconnect the 50-pin cable between 5i23 and 7i48 and scope pins 19 and 20, I get the behaviour I’m looking for: for pwmgen values above 0, pin 19 goes to 0 and pin 20 outputs a PWM signal changing duty cycle with pwm value - there’s something weird about the scaling but the waveform is correct as I understand it. For pwmgen below 0, 20 goes to 0 and 19 outputs the PWM. I think that’s how it’s supposed to be for type2 pwmgen, and that it’s what the Bosch drives expect.

The 7i48 is still reading encoders on all 3 connected axes perfectly well and supplying 5V to them.

I’ve tried using all 6 of the available AOUT/GND pairs but can’t get a response from the amp. Encoders appear to work OK on all 6 channels.

Is it possible that the 7i48 has failed on only the AOUT/GND lines? Am I missing something?

One other thing: at one point when it was working, I heard a pulsing in the vibrations from the motors, didn’t think anything of it as they aren’t tuned yet and buzz quite a bit, but then noticed a yellow LED on the 7i48 board going on and off in time with the pulsing. I can’t find any reference to that LED in the 7i48 manual - it’s at the bottom left of the board.

Any ideas?
 

Are the 3.3V, +15V and -15V LEDs illuminated?
(the 7I48 manual shows where these are)

Ah. 3.3V LED is on, +15V and -15V are not.

If the yellow LED near the corner blinks, that suggests problems with the 5V power
(maybe too much load from encoders if the 7I48 is powered through the 50 pin cable)

It blinked a few times as I described above, and I think has been off since, except a blink on during powering on - I'm away from the machine just now but will check asap.
Power was from the 50-pin cable until 2 days ago when I added an external 5v supply.
Is there anything I might be able to do about the missing +/-15v?

I cant remember (I will check on Monday) but I think the Yellow LED is supposed to be illuminated

Just to confirm that the yellow LED (CR8?) switches on for <1sec on PC power ON, but shows no other activity through starting linuxcnc, turning estop off, enabling machine, and returning back to all off.

I had a bit of time today to probe with a multimeter. The mini transformer has 5v between pins 1&2 and pins 2&3, 0v between 1&3, on the primary side. No volts between any pins on the secondary side, and nothing getting to the LM97/98 regulators beside the +/-15V LEDs.
So...maybe I've burned out the transformer?

Maybe some kind of 5V power issue damaged the transformer
The yellow LED on the corner does just blink at power up

Hi,

The replacement transformers arrived today; I replaced one and started the system with nothing but the 50-pin cable and the external 5V supply (which is from a spare SATA power line on the control PC motherboard) connected to the 7i48. The +/-15V LEDs lit up! Happy. Then powered down and attached the 3 servo amp command lines (on AOUT&GND0/1/2) and the 3 encoders to 0/1/2. No response to the jog keys, and before I could get to the multimeter to probe whether there was +/-10V at any of the AOUT/GND pairs, I notice the amp sound pulsing and the bottom corner yellow LED flashing again, and that the +/-15V LEDs were no longer lit. Took a quick video and powered down: photos.app.goo.gl/SrXj5qtoUYp9f65m9

You can see the LED flashing; if the amps are powered up, their humming pulses in time with that.

I noticed in the 7i48 manual it requires min 3K resistance across the AOUT/GND pairs. With amps powered off, I measure them at 65K and with amp on, 11K.

All 3 encoders were working, which I guess rules out a wrong-polarity connection on the 5V/GND lines to them.

I have one more replacement transformer to try...it's going to be pretty annoying if that repair only lasts 10 seconds too! Tomorrow I'll solder it in and go for attaching each of the 6 connections one at a time, and see if I can narrow down the problem. Any advice on what to look for or a different approach would be most welcome.

The only other thing I can think of is to do with the command wiring connection at the amp side. I've attached the Bosch Z15/25 amplifier manual; it talks about the command line connection across pages 8 and 9, saying 'for command values related to earth with only one command value line, this must be connected to terminal 9. Terminal 7 must then be connected to 0V (term. 8)". As I understand it, the 7i48 does not do this and instead switches the 10V output from one terminal to the other depending on whether it's + or -. The previous owner of the mill (who tells me the whole system was working when he last had it assembled, though this was 10 years ago) has amp terminals 7&8 bridged i.e. the cable screen connects to 0V as well as the -(+) line. Could this have damaged the 7i48's power supply? Seems like maybe yes...

Maybe answering my own question here then. Before I try all the connections again, I'll resolder the last spare transformer, remove the bridge between amp terminals 7&8, and probe the AOUT/GND before connecting it to the amp again.

Linuxcnc forum being a good rubber duck here!