MPC-1000 doesn't like supposedly-OK RAM

Hi folks,

I'm hopefully near finished refurbishing my first MPC. I think I bought a bit of a lemon because so far I've had to replace the pads, a couple of the tact switches, several of the buttons, etc. I bought it without a RAM upgrade. So far I've tried two SODIMMs, one bought from Amazon as MPC-1000 compatible and a second from MPCStuff.com, but both throw memory faults. Neither are labeled with their clock latency, but were sold as compatible. I have another SODIMM arriving hopefully later today that is definitely CL3, and a for-real made by Akai SODIMM showing up off eBay eventually.

I was just wondering if anyone else has seen an MPC with similar issues. I did ask mpcstuff.com and got the reply that their RAM is definitely OK, so it's probably the CPU board. I'm going to try the other RAM when it shows up, but I kind-of wanted a second opinion before I end up buying a second MPC as a donor since there don't seem to be any parted-out motherboards on the market.

I did look at the service manual -- it looks like the SODIMM socket is pretty much only connected to the CPU chip. I did clean the socket very carefully and I also reflowed the solder on each of its pins just in case there were any dry joints, but it made no difference. Has anyone seen a fault like this being caused by a bad GAL, or an actual bad CPU chip? It seems to me that it would be cheaper to replace them than the whole board. (Yes, I have surface mount soldering/desoldering equipment and would have no problem doing that, before anyone asks!)

Thank you in advance.

I have a MPCstuff.com RAM that doesn't work in my 1000 either. Fails test every time.

Aha. Good to know. I'll let you know whether the for-real Akai stuff works. Did you find any RAM that did actually work for you?

mgofmc wrote:Did you find any RAM that did actually work for you?

I have a second 1000 with the Akai 128mb and it works flawlessly. I really need to upgrade the other 1000. Anyhow it should work out for you.

I purchased a ram under a brand who's quality i trust and isnt taxed, samsung, off of ebay and it worked flawlessly. Which brand is mpcstuffs?
Hope your new one works for you man

I got some generic RAM off Feebay that works flawlessly. Make sure you are grounded when you install the RAM or you might zap it.

OK, so I finally got the new-old-stock genuine Akai RAM off of eBay. Nope, it doesn't work either. This makes four separate SODIMMs I've tried, so I'm now sure it's the CPU board itself. I have another MPC-1000 showing up off of eBay in a few days, so I'll do a parts swap to make one good one and probably keep the other one as a spare or maybe to use as a MIDI sequencer only, since that's fine with the onboard RAM.

dam! bummer man at least you're working it out. let us know what happens next, i'm interested to find out

I just got a second MPC-1000. I tried the RAM in that -- it all worked fine, so I swapped the CPU boards. The fault went with it, so my original MPC is now totally working, but I have a pretty much mint factory spec MPC sitting there now that is 16MB only -- it even has perfectly working original pads. I'm too busy right now to look into the fault more -- I have a Yamaha 02r console showing up next week that needs fixing more urgently. However, now I have two MPCs, one known good and one known bad, I should be able to probe the board with a 1GHz bandwidth scope with an active probe. The fault looks like a signal integrity problem, probably on an address line, though it could be on a chip select. By comparing the two boards it should be possible to figure out which line is iffy, and from that what chips are connected to the line. If there's an impedance mismatch causing the problem (e.g., an open termination resistor or a broken trace or some such), the scope should be fast enough to figure out where the reflections are coming from. It'll take a few hours, though, so paying work comes first!

My bet is on the CPU chip itself. We shall see.

godxbOmb wrote:I got some generic RAM off Feebay that works flawlessly. Make sure you are grounded when you install the RAM or you might zap it.

I have a proper ESD workbench, so no problems there.