Hi all,

I have a 1996 Yang Eagle/SML-12 with a Mitsubishi Meldas 50L control I am trying to get operating again. Long story short, it's been in storage for a while (>3 years) and I am only now trying to get it operational.

In typical fashion, the control battery died, so I replaced it and attempted to reinitialize the machine so I could get to re-inputting the parameters. CS2 to 6, wait for 7-segment to display 60, off, CS2 back to 0, power NC, set type and input power, power cycle NC, etc. However, the instructions say at this point the LCD should come back and start to display things in Japanese, so I'll need to change the language setting. Instead, I get a blank screen with only the cursor flashing.

I've tried a few things, like instead of returning CS2 to 0 after re-initialization, move it to 2 (manual says this pulls initial settings from EEPROM?) - no difference. Tried inputting other settings during that initial prompt immediately after reinitialization for the control type and input power, but there was no difference. I noticed immediately after reinitialization and before power cycling the NC, it does throw an alarm of S01 20 X, while the corresponding X servo drive status display flashes F1 20. I checked over the wiring to the encoder, but figure this is a bit of a red herring until I get the control parameters input in. As a test, I disconnected the servo drives from the main control and it has the same behavior of giving a blank screen after reinitialization, just throwing a Y3 01 -- error on the 7-segment instead over nothing being connected to it.

I called Mitsubishi Electric about this and one of the gentlemen there said the control likely needs to be serviced. Normally, whenever the NC is powered and not throwing an alarm like it does after reinitialization, it displays 0.4. on the 7-segment. The rep said this is a code indicating the control has had something interrupt the boot sequence and is hung up on it. I tried finding some sort of literature about this myself on the internet, but couldn't, so I'm assuming their techs have some more detailed information I'm not privy to. He also elaborated that the alarms were likely red herrings, but apparently there was a previous case file about a similar control needing capacitors replaced due to age-related failures, causing miscommunication with the servo drives. He suggested it was possible our control unit had a similar problem and to send it in.

I was a bit short on cash, having just paid for the rigging for the machine to bring it to its new location, so I decided to look into the control unit myself. Sure enough, I found a leaking capacitor. I believe it was the C17 one from my notes. I had an electrical engineer friend inspect the board, and his assessment was the C17 capacitor was the only one that leaked and there was no damage to the PCB. There was a neighboring -12V linear regulator that had some burnt residue on the pins, but this was likely electrolytic fluid dribbling onto it from that C17 capacitor and burning up when it shorted. I contracted his help in having the linear regulator and all but the largest capacitors replaced on the board as insurance and put the control back in the machine. Given the failed capacitor, we figured this was a slam dunk repair and it should resolve any issues the control had, but essentially, nothing changed. Still a blank screen after reinitialization and initial settings input. Now, we still do have those largest capacitors we can replace (the big 200v, 270uF snap in caps), but we skipped those over given how many smaller capacitors hadn't leaked yet (according to EE friend, the larger the capacitor, the less likely it is to burst, and he had also done a connectivity check as a rudimentary health check), so I'm doubting it will make a difference.

It's increasingly looking like I will have to send the control to Mitsubishi, but I wanted to consult with you gentlemen if any of you have experienced a similar issue. I've done a lot of fruitless searching to see if anyone else has gotten hung up in the same spot I have, but haven't come across anything yet.

Thanks,
Luke