"VACUUM ATMOSPHERES" Glovebox pedal fail, actually Mitsubishi FX1S PLC, or FX3S
PLC controller has one bad relay, the "V1" N2 gas valve either loud buzz or not being driven
SYMPTOM: no glove-inflate, one 24VAC Asco gas valve not working. We've seen this symptom on three different gloveboxes w/Mitsubishi PLCs, FX1S and FX3S. 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," 24V coil reads 4700ohms, but the contacts remain open-circuit. There must be major oxidation on the relay contacts.
GLOVEBOX: PN 101965 Vacuum Atmospheres Co. "Omni-Lab" 2004
PLC block: quite old "Melsec" FX1S-20MR-ES/UL Mitsubishi Electric, also FX3S.
N2 valves: Asco red hat OFKF8262G208, coil 24VAC. ON EACH VALVE, REPLACE THE LITTLE RED VARISTOR. If these fail, it applies full voltage-spike when relay contacts open. Perhaps the bad relay was killed by a failed varistor?
On FX1S model only, 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
- Hint: remove the bad one, then replace it with the unused eighth relay!
ABOVE: only seven of eight relay switch-outputs used!
On FX3S model only, 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.)
- Remove two plastic-tap corner screws, DON'T remove the black 5-pin port (goes to pressure sensor?)
- Use thin screwdriver to push in the four plastic catches, two on each side (one on right, one center-ish,) while gradually prying along the gap on both sides. Go slow, back and forth (you're unplugging a big multipin pcb connector.)
- Find eight relays on the bottom of the PCB: APAN3124 5amp SPST relays 24VDC coil, 5240ohms 4.6mA
- Hint: remove the bad one, then replace it with the unused eighth relay!
REPLACEMENT RELAYS:
I dissected a couple relays. Yes, the contacts are badly corroded after +10y of switching those big coils. (A varistor across the coil is REQUIRED. Failed varistors will shorten the relay contacts' lifetime, if the relays don't simply die of old age.
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
The FX3S plc uses the easily-found Panasonic APAN3124, 24V coil, 4.6mA, 5A contacts, same relay but with different pin placement than the RB-104.
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 and "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 120Vac (wh) (3 wires, two stacked fork-terms!)
- PLC-L 120Vac (bk)
wire labels AC pwr lower
- n.c.
- n.c.
- n.c.
- n.c.
- n.c.
- X1 (wh)
- S+S (bk)
- earth (gn)
