MPC3000 showing 8MB of Memory with 32MB installed

Clearly my 3.5OS MPC3K has some psychiatric issues. This is not the only problem I'm having with it.

I have 32MB installed and it only shows 8MB on startup. 93.4 sec of sampling. I have the optional EXM card removed. I have two sets of 16MBs to test with and one is brand-new. I have a hard time thinking it's the RAM and I have the exact same 8MB out of 32MB issue with both, but I'm happy to be corrected...

If I remove one or both of the RAM cards, 0MB on startup. The RAM appears seated OK and held by the clips. I feel like it would be an all-or-nothing situation were it not seated right, but it's consistently 8MB. So weird.

Any suggestions on where to start troubleshooting?

What happens when you try 1 16 meg stick only?

Hey Richie.

As mentioned it shows 0 MB of "Free Memory" for PGM, SND, etc. (top line of Vailixi System screen on startup) if I put only one stick (16MB) in. Tried both "front" (closest to user in front of the MPC) and "rear" slots. 0 for each! Registers 8060K with both 16MBs in.

Updated info: I swapped a friend's main CPU/memory board with mine. He's running 3.11 (I didn't have an IC puller so didn't switch OS) and my machine seems to work OK with his board in.

Long shot, but if I'm reading the schematics right, which is about a 20% chance, I noticed IC11 seems to have to do with the LCD display. That was the only IC that at least *appeared* weird to me on my MPC's main board...looked like there was either a spill or a little corrosion near one of the pins. I cleaned it with 99% iso alcohol but didn't replace it.

I also noticed that 3.11 seems to work the same as 3.5, which is if you have only one memory slot filled, it acts as if there is no (or at least not enough) memory. The error message was something like "There is not enough memory to perform this operation" when I went into the sampling page to check the length. But with my RAM in, it registered the full 32 MB, so it ain't the RAM. Definitely seems to point to something on the main board.

If there are any particularly vulnerable chips on there worth replacing, or that might have to do with this, please let me know. At least visually the RAM slots seemed clean and I couldn't spy any cracks in the connections to the PCB.

In order to make sure the corrosion is sanitized, you should first try with white vinegar then follow it up with the Isopropyl.

If you really want to make sure nothing is off, you can go so far as to reflow the solder in the given area with a decent amount of flux to ensure that the leads are clean, followed by what I mentioned above.

The only thing that comes to mind after reading your troubleshooting is considering that one of the memory mapper chips is not firing correctly, hence why your 3000 is only seeing half of the memory installed.

To be exact, it's showing 1/4 of the memory (I have 32MB).

Memory mapper...is that one of those custom Akai ICs or something else? Not sure which IC it is...

If I sound like I know just enough to really screw up a piece of gear, you've read me perfectly!

Wonder if it's time for another MPC. I think I was sold one that was abused and it's only really showing its scars now. I use lots of boxes and would use this mainly for individual parts...if it was my main workhorse I probably would have seen all the issues within a month or less.

If you sell it... hit me up.

[quote="kraftywerk"
Memory mapper...is that one of those custom Akai ICs or something else? Not sure which IC it is...

If I sound like I know just enough to really screw up a piece of gear, you've read me perfectly!
[/quote]

I'm not 100% but I highly doubt it's a custom IC. Most of the parts on the 3000 can be sourced (with varying degrees of difficulty) and replaced. Think of the mapper as a "controller" that handles the logic of how data is addressed from point A to B. So if one of them is not working accordingly, the 3000 simply won't see or understand how to use it.

I don't think you're doing sh*t to screw anything up from what I've read. Now to answer you which IC needs replacing, I do not know off hand. I could try to look at the service manual and figure out what chip does what however I have to admit that I am a bit limited in troubleshooting as I do not have the 3000 in front of me.

Although one point to look at is what traces are going from the SIMM slots and see where they lead. For all we know there could be damage to a trace at a micro level, so a good point to start at is working with a volt meter to check continuity. If this is out of your scope then this is where bringing it to a tech could serve you best. Or you can say forget that and be lucky enough to find a MPC 3000 mainboard to just change out and call it a day.

If someone else that has more experience with this can chime in that would be great.

When you had the expansion memory card installed (without the RAM sticks), did your MPC show 2MB or 8MB?

2MB...I think. Why?

Edit: I'll check but I think it was 10MB with the RAM sticks.