Mitsubishi Melsec AD76S - bad board?

[jdmcnulty 0]

Hello all,

I have an older injection molding machine w/ a mitsubishi PLC for the brain. We recently have had a problem where the machine will not allow us to power on the heat or hydraulic pump. We've verified all the electrical drawings, and everything is correct.  Fuses are good, breakers are not tripped.  When the machine first turns on, it sounds a 5 second buzzer - indicating a problem w/ something.  The error on the screen states Alarm 08 - Digital Valve Control Unit (AD76S) Alarm.  This points to the AD76S board. The troubleshooting column simply states if the power is off on the board, the fuse is likely blown.  In our case, the light is on, the fuse is good.  Any way we can test this board?  We have also tested our output board for the heater / power controls.  I bypassed the pump on relay - the pump fires up, but we have no motion out of the machine.  The lights go active on the input board when we press movement actions - but the hydraulic valves do not actuate...  Thoughts?  Anyone know where I can get one of these boards?? Thanks, Jason

Edited 29 Oct 2017 by jdmcnulty
Fixed typo

[kaare_t 155]

Are you sure that the alarm you are referring to is actually pointing towards the AD76S card? You are writing that the alarm is ADS76 which is not the same as AD76S... The reason I'm asking is because the AD76S card is a motion controller card, which probably has nothing to do with any hydraulic pumps or any other direct digital controls. If it's an injection molding machine I would suspect that the AD76S controls variable movement of some sort, for example the movement of the dies going back/forth. My guess is that there is something else than the AD76S which is broken...

[jdmcnulty 0]

My mistake, I must have fat fingered the keyboard.  The error 08 states that digital valve control unit (ad76s) is alarming.  The cause is either one of the following 3.  First, ad76s, second if power is out on the ad76s board, the fuse could be bad.  Third, something related to wiring. 

 

My power light is off on ad76s. But the fuse is good..  I've tested and even swapped with the one running plc.  

 

I should mention. The press was running fine up ubtil last week. Went to turn it on, and now we have issues.  

[jdmcnulty 0]

Fyi. Purchased new ad76s board. Fixed problem. 

 

Will attempt to repair old board.