New Zealand Vintage Computer Forums

Hi All

I've found a suitable replacement edge connector for the Sega SC-3000 if anyone ever needs to replace one due to bent / broken pins.

Sullins EEA22DTBN
www.sullinscorp.com

EEA22DTBN (PBT / Tin plated contacts, 22 pins, dual sided, 0.180" tail
length, no mounting ears, 0.610" body height, 0.370" body depth, 0.150"
row spacing, right angle mounting).

I put a bit of super glue underneath the edge connector before soldering it in to help take some of the strain when inserting / removing carts. The original connector had some sort of adhesive there too which I had to lever up with a screwdriver when removing the original connector.

Note - I've only done mechanical fit tests and basic continuity tests to the pins at the back of the cart as this SC-3000 mainboard is dead. The fit is a bit tight on the carts, but I assume that will loosen up with use.

The EEA22DTAN could be a slightly better alternative. That only has 0.100" tails instead of 0.180" tails, as the 0.180" pins poke a fair way through the mainboard.

Note also that the row spacing on the SC-3000 is 0.125", not 0.150". But the pins bend into place so easily you might not even notice the bend if you didn't know the spacing was out.

The insertion depth of the cart PCBs into the slots is a little shallower than I would like, but it still seems to get an acceptable grab on the cart contacts, although only about the last 1-2mm or so.

I'd just like to say a huge thank you to Lucinda over at Sullins Connector Solutions who helped me narrow down the choice of connector.

Cheers

You can see photos over at

http://www.smspower.org/forums/viewtopic.php?t=14114

machinecoder wrote:NEVER USE SUPERGLUE for anything other than lifting elephants !!!! It leaves a white mist/coating on all the surrounding parts, and could have coated the contacts of the connector ! Just my two cents worth

Ta, point taken. I know the mist / coating you mean. I have no idea what damage that might do to components or soldermask, but it could be a pain to remove.

I think I'm ok in this case though. The Sega SC-3000 PCB is one-sided, so there is no soldermask or copper on the side that I attached it to (the top side of the PCB is components only and has a gazillion adorable hard jumper wires instead of traces - that would have been a real pain to assemble, so there must have been a significant cost saving to a one-sided PCB in 1983). And the connector body is quite wide, so the glue is well away from the contacts. Ideally you want a glue that is strong enough to take the strain, but weak enough to break when flexed if you have to lever the connector back off again. The original glue looked a bit more like Selly's multigrip - slightly rubbery. But I couldn't find a tube of that around the house

Here is the datasheet for future reference.

http://www.sc3000-multicart.com/downloa ... nector.pdf

Truly great piece of information! Both my SC3000s are finnicky old goats of things to get running as the card connectors are pretty badly worn. That happens when you're 30 years old and cartridge based though I guess

Note - I've only done mechanical fit tests and basic continuity tests to the pins at the back of the cart as this SC-3000 mainboard is dead. The fit is a bit tight on the carts, but I assume that will loosen up with use.

This SC-3000 is working great now, and I can confirm that the replacement edge connector is working well with multiple different carts. Description of the fix follows below.

When I plugged it in, I got some sort of video signal. But instead of the normal black screen and 'medium tone' that you get with a SC-3000 with bad cart insert, I was getting a blue screen and slightly different tone. No music from games carts. I check the voltage to the VRAM ICs - something around 3v.

The 5v regulator was stuffed - it was only putting out around 3 volts. Once I replaced that, some of the carts would sort of work, but they had memory errors. I isolated that by testing with the multicart. It worked perfectly with the multicart which has its own 32KB of SRAM on board, but you can also disable that with jumpers on the multicart and force it to use the SC-3000s on-board 2KB SRAM. As soon as you used the SC-3000s 2KB SRAM the weird problems with games and the cart menu system started again. You can perform similar isolation testing with a BasicIIIB cart. A Basic IIIA cart gives a memory error (2 beeps repeated) in this situation because a Basic IIIA cart actually uses 18KB of RAM - 16KB on the cart from $8000 to $bfff then the 2KB of SRAM on the SC-3000 from $c000 to $c7ff.

I sourced some NEC D4016C chips which were the cheapest pin compatible replacement I could find for the original MB8128. I removed the original chip last night with solder wick then socketed and replaced with a D4016C. Works great now.

I got that motherboard in a garage sale back in about 1999, and it was dead when I got it. So I'm quite happy to get it up and running again

Congratulations! A great bit of restoration work!