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lagomorphonic

SE/30 Unstable behaviour after 128MB RAM install

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Thickness is the issue I think.

I have a few cheapo ROM SIMMs in 1.2mm and 1.6mm thickness. The first is too thin to make good contact and the latter will only fit into the slot with some force.

The original seems to be 1.4mm if I remember right.

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Not tried it yet lago the wife had other plans for my evening and not in a good way, chores and being taxi to the kids oh well, anyway interesting :/ is it poor design then as surely 95% of them would be used in se/30’s at the prime candidate for needing 32 bit clean rom and having 128mb expansion capabilities? I suppose we should be happy someone even designed it at all!  Ok I’ll get more bands from work and maybe some blutac as a wedge. Thanks for that as I don’t want to keep opening the case.

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My memory says that old time SIMMs should be .050" thick which is .050 X 25.4 = 1.27mm.    So one should probably aim for 1.3mm.

 

1.6mm would be the more modern .063" thickness, which is what the PCB companies default to.   If you don't specify, you get 1.6mm thick.   I don't think it should be possible to wedge 1.6mm board into a .05" socket.

 

Unless there's more than one kind of 64 pin SIMM socket?

 

When I ran off my batch of IIfx SIMMs, I specified .05" thick and they fit the sockets just right.  I've never tried plugging one into a ROM SIMM socket though.  I'll try to remember to do that when I get home.

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I put one of my unpopulated IIfx SIMMs into a IICX ROM socket and it fit very snugly, but properly.   I should have thought to try one of the ROMinator SIMMs I have in the same socket for comparison.   Anyway, point behind last night's test is that .05" thick works great in the IICX ROM socket.   Leaves me wondering what thickness was used for the ROMinator.   I would have tested in an SE/30 but don't have one easy to hand at the moment.  The IICX should have the same socket installed.

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Okay, tried the ROMinator SIMMs in the IIcx and they fit less snugly, but the fit seems good enough.  I don't think elastic would be needed to make it work.  

 

The ROMinator looks slightly less thick to the eye than my .050" boards, but putting them edge to edge, I can't feel a difference.  

 

I wonder if the difference in thickness is .047" vs. .050".   I've seen some PCB houses offer .047" instead of .050".   I'm not sure how much difference 3 mils would make.

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On 7/9/2018 at 9:34 AM, lagomorphonic said:

SE30_Neal if you're going to use an elastic band you'll need to make sure it *really* pulls on the card. I had to triple up the bands on mine and still occasionally will need to press on the ROM-inator on bootup (the corner of is is just barely accessible if the case is open. Get something non-conductive and press it forward if the rubber bands alone don't work just to see if that's the problem). Ideally I will put some tiny solder blobs on each of the pins at some point to help maintain the tension. It's a bit annoying that these are "known to be faulty by design" for use in the SE/30 considering it is probably one of the most desirable old Macs for it to be used in.

So logo are you saying i need to solder blobs to the contacts at the bottom for better contact? I have no problem with getting that does as i cant be doing taking it apart all the time? 

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1 hour ago, trag said:

Okay, tried the ROMinator SIMMs in the IIcx and they fit less snugly, but the fit seems good enough.  I don't think elastic would be needed to make it work.  

 

The ROMinator looks slightly less thick to the eye than my .050" boards, but putting them edge to edge, I can't feel a difference.  

 

I wonder if the difference in thickness is .047" vs. .050".   I've seen some PCB houses offer .047" instead of .050".   I'm not sure how much difference 3 mils would make.

Hi trag I believe its an se/30 only issue the rominator site mentions a simm shim for se/30 but I’ve googled that i get nothing so I’m at a loss about what that is

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If you decide to solder little blobs onto the SIMM be sure to solder them onto the backside, otherwise it might actually make things worse for some SIMM sockets.

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19 minutes ago, Bolle said:

If you decide to solder little blobs onto the SIMM be sure to solder them onto the backside, otherwise it might actually make things worse for some SIMM sockets.

Thanks Bolle, back side, is that the side with the skull or the side with the chips?  Do you think blobs of solder will work?

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I have done so on some of my ROM SIMMs and it makes it better (but still not really 100% perfect)

Backside should be the one without chips. The front of the ROM is facing towards the burn-in connector of the logicboard when inserted into the socket.

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Ok thought so im no electronics person but my sister is ex ministry of defence electronics specialist so I’ll get her to solder it for me otherwise there’d be blobs every where lol do you need to add much? If i grt it soldered and use bands hopefully that will be enough :)

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Thanks Bolle, that really helps being able to see it, yes i see its a bit of pain but think i get this done the weekend.

 

brilliant i hope it’s enough :)

 

neal

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22 hours ago, joethezombie said:

 

 

If you download the ROMinator II manual, it details the issue on the last couple of pages.

 

Ah, got it, read it.  I see that the manual clearly states the socket in the SE/30 is a little different from in other models.

 

I think I may experiment with replacing the ROM socket with a new one.

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37 minutes ago, trag said:

 

Ah, got it, read it.  I see that the manual clearly states the socket in the SE/30 is a little different from in other models.

 

I think I may experiment with replacing the ROM socket with a new one.

Yes i read that too but only after buying it and unsuccessfully installing it, taking the simm to my sisters this weekend to add solder to the contacts to help it fit better.

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I've tried everything from the paper clip "spring," to the rubber band, to a trimmed-down plastic card/shim and the fit still leaves something to be desired... sometimes mine doesn't chime at all or, if it does (after a whack to the right side), it's not stable until I pop the case, take out the board and give the ROM a tune-up, fit-wise. I don't blame Doug for the design at all - it's got to be a tough supply chain and next to impossible to capture like .76 mm (the difference between .50" and .47" as you noted above) like 25+ years later.

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