[DarrylO]

Hello everyone,

I'm new to the forum and hoping to get some assistance with an Amada press brake I recently purchased. The machine is equipped with an NC9-F controller and a Meldas FCA321 SN#M320 numerical control.

Currently, I'm facing a display issue: the screen turns on, but each letter appears as a solid block rather than a properly formed character (see attached picture).

I've already taken some steps to address the problem. I replaced the old CRT with an LCD, which improved the display quality but didn't resolve the issue. I also swapped out the MC201B board, which the screen connects to, but that didn't make any difference either.

My next step is to consider the Meldas numerical control. The MC201B board plugs into the MC721 cassette of the FCA321. Would it be worthwhile to replace this component, or could the issue be something else entirely?

Thanks in advance for your help!

Best regards,
Darryl

[MrMetric]

The 201 board doesn't really have any active logic on it that relates to the display. The board just routes the video signals from the one connector to the video connector, effectively acting as a signal splitter.... One thing you have not considered is a bad cable or connection. I'd have to look the boards up because my M3 uses a different stack, but the upper left in the card cage is where my video card is located. This is where you have the MC631. It would not surprise me one bit if that were not the video card in your case too. Mitsubishi has so many different boards, however, that I cannot tell you the difference from one to the other. I think I have a spare 320 card cage, though, that I might be able to look at this weekend... I believe that on my system, and I suspect yours too, the video card really only serves one function and that is video signal generation. That is relevant because you can, in theory, build a test cable that plugs directly into it and thereby can be used to determine whether or not the card is working.

I think the video card may have an EPROM in it, but I'm definitely iffy on that. If this is the case, then it is possible that the card is fine but the EPROM itself has bit corruption. These systems are pretty old and EPROMs don't last forever. Getting a new EPROM image shouldn't be that bad, though. If I have the board, I can make a copy for you (and I'm pretty sure I have a 320 cage that I picked up as a spare awhile ago).

I don't know about the color display, but I can tell you that the monochrome consists of three singals... video, horizontal and vertical. There is an open source project that has a configurable input to HDMI. This allows a person to use an off-the-shelf video monitor if you have the correct configuration. It works pretty well. The bigger problem is that the Mitsu display are not 16:9 which is what almost all new monitors are. But it looks like you have an industrial monitor anyhow which has a similar signal converter built into it.

[DarrylO]

Mr Metric, great name for the USA.

I had semi considered a bad cable connection... I didn't consider it enough to test it though... so you'd be right in saying that.

Interesting you bring up the EPROM, I didn't want to bloat my original post with he said/she said but the person I purchased it off was completely unsure about the problem also but vaguely mentioned the EPROM.

I picked up the industrial monitor for ease TBH as I just wanted the machine operational. its is a direct plug and play into the 201 board and so far (as far as I can tell) works exactly the same as the CRT but better. (not knowing if its the right thing at this stage, potentially removing as many old boards as possible might be a better answer)

To assist what would I be looking for to see if the MC631 is the correct card containing the video card / EPROM ?

how can I go about testing this? excuse my ignorance, I'm relatively new to old CNC equipment.

Appreciate your reply!

Cheers
Darryl

- - - Updated - - -

Mr Metric, great name for the USA.

I had semi considered a bad cable connection... I didn't consider it enough to test it though... so you'd be right in saying that.

Interesting you bring up the EPROM, I didn't want to bloat my original post with he said/she said but the person I purchased it off was completely unsure about the problem also but vaguely mentioned the EPROM.

I picked up the industrial monitor for ease TBH as I just wanted the machine operational. its is a direct plug and play into the 201 board and so far (as far as I can tell) works exactly the same as the CRT but better. (not knowing if its the right thing at this stage, potentially removing as many old boards as possible might be a better answer)

To assist what would I be looking for to see if the MC631 is the correct card containing the video card / EPROM ?

how can I go about testing this? excuse my ignorance, I'm relatively new to old CNC equipment.

Appreciate your reply!

Cheers
Darryl

[MrMetric]

Sorry about the late response. I thought I did this but realize now that I did not....

Never discount the value of wiggling the connector or cable to see if there is any change in the visual attributes of the screen. If things "change" then it could be an indication that you have a poor connection or broken wire someplace.... Next up would be to actually build a test cable so that yo can try the display straight out of the control. The video is really not that many signal lines, so it should be an easy cable to build. if you have the same problem with a new cable, then it is a fairly safe bet that your other cable is fine too. I would then say that it is likely your video card.... To get information on the video card and the pin assignments, you will need a Mitsubishi systems manual. Those are on the meau website.

Found it... Here is the pinout of the connector on the MC721 board:

[DarrylO]

Hi there, not a problem!
so I've tested the original cable and nothing strange, as well as I made a test cable to confirm and this changed nothing, still the same problem and no glimmer of hope.

I cant seem to access the Meau website for some reason?

I've attached some images of the other boards mentioned previously. just for reference. I assume now I need to replace / repair / reflash the video card? what would you recommend to do next?

Thanks again!

[MrMetric]

Based on what you are saying, you have eliminated the cabling. As such, the issue is likely in the MC721 or in some connections. I would reseat all off the boards and try again. If that doesn't work, I'd probably be looking for a spare MC721 for cheap. At the end of the day, you often end up in a situation where you have to take a gamble and do some A/B testing after having thrown some money at the problem. It isn't ideal, but we don't have perfect schematics or troubleshooting abilities. Mitsu doesn't publish exacting means of diagnosing issues. Sometimes you win, sometimes you don't....

[DarrylO]

I have re-seated / cleaned everything but... no change.

Im happy to buy a used but good MC721, so I will order one and go from there. is there anything I need to look for? matching chip numbers or anything?
where does the video card get its information to display i.e the amada press brake program?

Cheers!

[MrMetric]

I don't know the Amada system, but typically no.... The display is the domain of the Mitsubishi control system. That is "customized" by configuring Input/ouput pins and through custom PLC programming. But those all essentially affect the way the Mitsubishi control handles inputs, not actually what it does with the inputs. Hopefully that makes sense... Whatever the case, the CPU tells the graphics controller, in rough terms, what to display on the monitor. The graphics card (MC721) is responsible for generating the signals to ultimately render the image that the CPU is wanting. Given that your system appears to be working (as best as I can tell, but remember, this is like you getting on the internet and asking a dentist 2000 miles away, "my tooth hurts, do I need to get it extracted?"), other than the display is just not rendering properly. To that end, I would think that the most likely source of the problem is somewhere between the CPU and the wires going out the connector on the MC721. I say this because you have already eliminated the cable and the display by having confirmed the same behavior with a different set of cables and display. I tend to not think the issue is in the backplane or connectors for a few reasons. First, those are gold contacts and are generally pretty stable; so if there is a problem, it is usually something like a bent pin on the board (which, you should look for.... hint hint). Second, you appear to have blocks of in the same places you should have characters. But those blocks are positioned by the CPU too. There is just too much going on that looks like *is* getting from the CPU to the video card to make me think there is an issue in the connectors. However, the key is to remember that we are always working with a degree of probability. You never rule anything out completely, but you do move the likelihood of an error down the stack or up the stack accordingly. So, if you came back and said, "Alan, you are an idiot.... the issue was with the connector...." I'd respond, "OK, I am a little surprised but whatever..." And, of course, I'd then tell you that you clearly hired the wrong (amateur) repair man to fix your problem anyhow!" :-)

Fixing stuff remotely is very very difficult most of the time... From my perspective, though, I think I'd be looking at buying an MC721. If you are in the States, you can find them for fairly low prices on eBay.