V350 failed analogue outputs?

[NickButt]

Hi everyone

I have three V350-35-TA24’s running identical wiring, programming, jumpers etc. They have been running trouble free for 5-6 years up until now, controlling fluid pumps.

One of them has seemingly experienced a failure of both analogue outputs. The jumpers are still in place. Digital outputs still work fine. Inputs work fine. This output was using 4-20mA to control a proportional pressure regulator.
I have swapped the faulty unit out with the other two working units and the fault follows along. I have only ever used A0, and so tried switching to A1 but still nothing. A1 had never been used prior to this. I think these would be individually fused? I have re-loaded the program in-case some sort of file corruption had occurred.

The only thing I haven’t tried, is swapping out the plug in I/O board with one of the other known working units, to find out if it's the I/O or the PLC itself. I am nervous about trying this as I can’t afford to have a second one fail if something has caused a component to blow. 

I’m 99% sure this is a hardware failure. Does anyone have a suggestion of something to check, or is it likely toast?  Is there a schematic of the board available? Is it possible to buy just the I/O board?

Regards

Nick 

[TozoM8]

No suggestion how to fix it, but rather a good practice. I use the same screens, snap on modules and extension modules on all my machines.  In some cases it might be an overkill, but keeping a spare (or 3 in this case) eliminates downtime. Btw I have not had a failed unit in 8 years. 

[kratmel]

I don't know how experienced you are in electronics.
However, if you have a digital voltmeter, the only thing you can check is the 15V supply voltage of the analog output chips.
There is a 78M15G chip on the I/ O board.
Find the instruction for this chip and measure the power supply at its input (should be 24V) and 15V at the output. (Any quastion in PM).

It is clear that all actions you take at your own risk.
Probably the only thing that can be advised in your situation.
In my experience, there have been cases of failure of just such a chip in different device.

However, a qualified electronics technician must repair and change something in the circuit (even such "big" chip).

The best way is to replace the PLC with a new one.

[Ausman]

Also, just in case it has had a spike etc that has somehow upset things, have you tried loading a blank program, Init and reset, reload yours, Init and Reset?  And do this also having the upload ability active as well.  I doubt that this is going to help, but is worth a try.

If that doesn't fix and it looks like hardware failure of both, that seems a little odd and I'd be carefully checking things down the line.  Maybe you've developed dud connections somewhere that have let stray voltages in.  Maybe the pressure reg has developed an issue.  Or perhaps time has let other crap fall onto terminals.  Or a worker drilled metal nearby and swarf fell onto terminals, and they then went oops and brushed it away..."No, not me".  Or the nasty fairies flew past and waved their wands as they chuckled at their mischief.

cheers, Aus

[kratmel]

17 hours ago, NickButt said:

I have three V350-35-TA24’s running identical wiring, programming, jumpers etc. They have been running trouble free for 5-6 years up until now

Please check 24V voltage power supply on broken analog output installation.

I case great overvoltage (5-6year power supply can do little joke) >>>28V - linear power IC (78M15) in smd package can desolder himself....

  

[NickButt]

On 11/1/2020 at 7:29 AM, kratmel said:

I don't know how experienced you are in electronics.
However, if you have a digital voltmeter, the only thing you can check is the 15V supply voltage of the analog output chips.
There is a 78M15G chip on the I/ O board.
Find the instruction for this chip and measure the power supply at its input (should be 24V) and 15V at the output. (Any quastion in PM).
 

Thanks Kratmel, I located the chip and measured 24v input but only 1v output.  
Also, 24v power supply is measuring correct 24v. 

Thanks Ausman, everything looks solid and clean. I think it it can only have been the nasty fairies.  

Thank you to those who responded. 

[DanT]

Hi;

 

Comment for future :

from the comment  in 1st post :  The only thing I haven’t tried, is swapping out the plug in I/O board with one of the other known working units, to find out if it's the I/O or the PLC itself. I am nervous about trying this as I can’t afford to have a second one fail if something has caused a component to blow. 

The I/O board Analog Inputs and Outputs are factory calibrated and data stored on the Main Board.

Swapping I/O board with another unit's I/O board will mess up that calibration, and Analogs May Not Work at all.

 

DantT

[kratmel]

11 hours ago, NickButt said:

I located the chip and measured 24v input but only 1v output.

Then, on power off state,check - is the IC output shorted. If not,  You can try to replace IC.