Today I’ve got some fresh work I’ve been dealing with. As part of troubleshooting a Sega Mega Drive 1 VA4 PAL unit which is faulty – for which I’ll be posting something about sooner or later – I’ve been unsoldering the Video RAM from (my) PAL VA6 working unit to swap and test the VA4. When I unsolder ICs, I typically socket everything up by then, as unsoldering is a stressful process for the PCB, and I don’t want to end up with a “oh oh” situation where the part was not the culprit, or worse, only to discover I’ve soldered the bad one with another BAD one due – this is > 30years NOS anyway, you never know what you get.

Sega Mega Drive 1 Video RAM retrospective

Anyway, the 2 Mega Drives have different model and manufacturer parts, but they are 1:1. Specifically:

Feature	Fujitsu MB81461 (VA6)	OKI MSM51C262 (VA4)
Organization	64K x 4-bit (Dual Port)	64K x 4-bit (Dual Port)
Total Capacity	256 Kbits	256 Kbits
Technology	NMOS (typically)	CMOS (typically)
Pin Count	24-pin	24-pin
Voltage	+5V	+5V
Package	DIP or ZIP	DIP or ZIP

Note: I got the Fujitsu in the VA6 and the OKI in the VA4.

Additional note: Even though the Fujitsu is labeled as 120ns and the OKI as 100ns, I was pretty confident the swap would have just worked. I’ve seen this already: as supply chain is always delicate and hard matter, Sega must have made deals with multiple manufacturers which provided whichever was on stock first, within an accepted tolerance for the Mega Drive. Based on facts here, I’d say that’s 120ns, worst.

What’s this ZIP highlighted above?

As you all know, or noted in the ZIP [0] highlight above, Sega had some odd fetish for this infamous ZIP packaging, which allowed for smaller spacing on the PCB against components being vertical mounted. I’ll call “Tower of Power” [1] inside the console.

So what’s the hussle?

While unsoldering the VA6 VRAM, no problem at all. Same goes with the VA6 for the first RAM. Then goes the second, which wouldn’t just leave the PCB, even with soldering paste or flux. I had to push a little…and eventually it got 4 legs broken…3 were still on the surgery table, the last one went missing…as in Monkey Island 2: Le Chuck’s Revenge ending (see the end of the page).

As I didn’t have any spare of these – otherwise I wouldn’t have goone for the soldering job in the first place – and I didn’t want to wait another ~ 10 days from Aliexpress to source some, I just had one option. Refurbish them!

Here goes nothing

The metal part was still in the memory packaging, that’s the only important thing when it comes to salvaging this stuff. I’ll post something more wild on this some day.

The only thing needed was just some steady hand, soldering skill, small soldering iron (FYI I used a Weller WLR21 with my WSD50 soldering station, 0.8mm tip), and some flux to make this out…and so I did.

First I removed the soldering paste residue – IPA, contact cleaner, and the iron itself did it. Then, I had to align the pins again, as we started with this situation here:

Much better now:

And now on with the soldering. In the process one other leg got lost, making the count to 5. In order to work the piece out at a decent height (steady hand, remember?) I’ve just temporarly taped on top of the tip spool. Some moments later, and…there we have it.

Of course, not having to solder this on the mobo, but to simply put it into a socket, helps A LOT, otherwise the repairing solder would just melt in the process.

Note: I would share a piece of advice here. As many vias are on top of the motherboard, it’s safer to start soldering sockets from the top, and not from the bottom. Then, solder again on the bottom, as the resulting soldering job would suck there, see the second pic.