"VACUUM ATMOSPHERES" Glovebox w/Mitsubishi PLC,
PLC controller has one bad relay, one N2 gas valve not being driven
SYMPTOM: no glove-inflate, one 24VAC Asco gas valve not working. One failed relay inside the Mitsubishi PLC Programmable Logic Controller. (It contains eight tiny relays, with contact-lifetime shortened by driving inductive 24V AC coil-loads.) The bad relay does "click," coil reads 4700ohms, but the contacts remain open-circuit.
GLOVEBOX: PN 101965 Vacuum Atmospheres Co. "Omni-Lab" 2004
PLC block: quite old "Melsec" FX1S-20MR-ES/UL Mitsubishi Electric
N2 valves: Asco red hat OFKF8262G208, coil 24VAC
Accessing the internal pcb relays:
- Remove 120VAC, unscrew all PLC wires (take pictures, write down wire lables!)
- Remove two nuts to remove PLC from glovebox (used tiny screwdriver to pry nuts sideways, loosen.)
- Open tiny door on PLC top, remove one screw from tan plastic (NOT the screw in the green pcb.)
- Pry up the 1.5" square plastic cover from the top (it's held in by four tiny snap thingies)
- Remove the long screw (NOT the screw on the small green pcb)
- Pry off the entire main cover (held in by three little snaps, visible through vent-slots.)
- Remove one screw from main PCB
- Pry up the main PCB by spreading the plastic case slightly with thin screwdrivers (it's held in by horizontal vent-slots in the sides of the plastic case.)
- Find eight relays on the bottom of the PCB: RB104-DE 6amp SPST relays 24VDC coil, 4700ohms 5mA
REPLACEMENT RELAYS:
Original: RB104-DE 24V coil, 5mA, 6A contacts, Fuji Electric
Other replacements:
* RB105-DE 24V coil, 8.3mA, 6A contacts, Fuji Electric
* RS4N-DE (large relay assy., contains four RB105-DE)
* G6DN-1A-SL DC24 24V coil, 5mA, 5A contacts Omron
* G6DS-1A-H DC24 24V coil, 5mA, 5A contacts Omron
* PCN-124D3M 24V coil, 5mA, 5A contacts Tyco
* PA1A-24V 24v coil, 7.5mA, 5A contacts, Panasonic
NOTES:
On youtube there are tutorials for downloading the SW contents of these PLC blocks. First must build/buy an RS232 programming cable. (I don't know if the glovebox's own DIN cable can be used. I don't know if Vacuum Atmospheres has blocked our ability to read ad "clone" their pgm into new replacement PLC-units.)
NOTES:
Wire labels upper (eight relays)
- n.c. (w/unused new relay inside!)
- Y6 (n.o. to COM4)V5L (bk)
- Y4 (n.o. to COM4) V2L (bk)
- Y3 (n.o. to COM3) V1L (bk)
- Y2 (n.o. to COM2) (wh/bk)
- Y1 (n.o. to COM1) (wh/vio)
- Y0 (n.o. to COM0) (rd)
- 0V (-24V) (bk)
wire labels lower (eight relays)
- Y7 (n.o. to COM4) V6L (Bk)
- Y5 (n.o. to COM4) V3L (Bk)
- COM4 (to Y4, Y5, Y6, Y7) (Bk)
- COM3 (to Y3) (Bk)
- COM2 (to Y2) (Bk)
- COM1 (to Y1) (Bk)
- COM0 (to Y0) (Bk)
- +24V (Rd)
wire labels AC pwr upper
- n.c.
- n.c.
- n.c.
- n.c.
- n.c.
- x0 (bk)
- PLC-N (wh) (3 wires, two fork-terms!)
- PLC-L (bk)
wire labels AC pwr lower
- n.c.
- n.c.
- n.c.
- n.c.
- n.c.
- X1 (wh)
- S+S (bk)
- earth (gn)
