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Socket specs for MMU and OS Rom?


Dantaipan

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2 hours ago, yodan said:

@flashjazzcat is there anything else I should have socketed on this board while doing this?

50F14561-6017-4F19-AD6C-C819D7CF6439.jpeg

Nothing that isn't already socketed, except perhaps 74LS08 (just in case you later plug a SIDE3 in the machine and it requires a 74F08 instead, although this is usually only necessary on XEs when it's necessary at all).

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My pennies worth. I've found that getting the precision round sockets is better than standard, say, double wipe sockets. The U1MB's supplied harting ribbon end connectors fit snuggly into the round type on account of having round pins themselves, but can potentially pop out if you go with standard sockets.

 

I've used these in the past on many U1MB installs:

image.png.e00697b2ce8ecc3b79b66ca2a568d00d.pngimage.png.1ef55000c75c4a52ea1cb3e1aca8a6ff.png  

 

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7 hours ago, Beeblebrox said:

My pennies worth. I've found that getting the precision round sockets is better than standard, say, double wipe sockets. The U1MB's supplied harting ribbon end connectors fit snuggly into the round type on account of having round pins themselves, but can potentially pop out if you go with standard sockets.

Thanks I had actually ordered some just like that. Leaving links here for anyone in NA looking into this:

https://www.digikey.ca/en/products/detail/adam-tech/ICM-320-1-GT-HT/9833006

https://www.digikey.ca/en/products/detail/adam-tech/ICM-628-1-GT-HT/9832982

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Precision sockets are great, but there was a very interesting 'Adrian's Digital Basement' video recently in which he did a marathon repair on a C64 board which appeared to have a bad PLA after the character ROM had apparently been removed and socketed using a flame-thrower by someone else. He replaced the socket and repaired a couple of traces (the PLA issue being a red-herring), but along the way had his first experience of poor connectivity regarding desoldered chips in precision sockets. Only an EPROM would work in the socket; the original masked ROM was a no-go. I've run into this issue several times before, and although I try to use precision sockets wherever possible, I've had all kinds of problems with desoldered chips (even after cleaning up and leg-straightening) not making proper contact in precision sockets.

 

I guess one piece of advice is: buy good-quality precision sockets.

Edited by flashjazzcat
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It never hurts to give the dram chips sockets for easy replacement and simple chip swapping to quickly find the culprit or even for testing basic functionality of dram.

 

I have made a habit of installing sockets for all IC's on all my boards and at the same time replacing old 74LS series chips with newer, more efficient 74F series as the old ones die eventually anyway, especially under my regular use. I only recently started using 74F series, before I used 74HC series, and still do until I run out what I have on hand. Some may consider all of this overkill, I just consider it over re-engineering for longevity.  Or maybe just bringing it all up to true, original engineering specs as much as possible, reversing cost-cutting measures from manufacturing. As far as the sockets go anyway; obviously the 74F series weren't available to the original engineers.

 

As far as sockets go, in my personal experience I find that precision sockets are best with precision pins (both round). And that for microchips with flat pins (de-soldered or new) the standard double-sided sockets are best. I stay clear of single-side sockets and replace them when I run across them. Round with round makes the best contact and flat with flat too. Using flat (or square) pins in round sockets never made sense to me, even before trying it, as even if the pins fit in snug, you still only have the edges (or corners) of the pins making contact with the round sockets. The more surface area making contact the better, always.

 

The most optimum of course is round precision sockets with round pins. Unfortunately most DIP chips, standard or custom, from the 8/16-bit era have plat pins and high-quality double-sided sockets are the best for them.

Edited by Gunstar
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1 hour ago, flashjazzcat said:

Precision sockets are great, but there was a very interesting 'Adrian's Digital Basement' video recently in which he did a marathon repair on a C64 board which appeared to have a bad PLA after the character ROM had apparently been removed and socketed using a flame-thrower by someone else. He replaced the socket and repaired a couple of traces (the PLA issue being a red-herring), but along the way had his first experience of poor connectivity regarding desoldered chips in precision sockets. Only an EPROM would work in the socket; the original masked ROM was a no-go. I've run into this issue several times before, and although I try to use precision sockets wherever possible, I've had all kinds of problems with desoldered chips (even after cleaning up and leg-straightening) not making proper contact in precision sockets.

 

I guess one piece of advice is: buy good-quality precision sockets.

I watched that episode in horror at the state of that PCB, what a mess it was. I know the guy that sent them to Adrian, he's a scener, I've got to ask him if he did that to it..

 

Re the sockets, yes was a shock to see a no contact with the chip, the sockets with the round holes which I know as wire wrap sockets, now precision, are normally a better contact because of the fact they are round so it takes a bit more force to get the legs in it, very snug fit, so I was shocked when it wasn't working. Obviously as you say, a round pinned chip would be ideal.

 

 

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Well that's embarrassing, got my Henning and Hedning mixed up...Not the bloke I thought it was but not before messaging the guy and taking the mickey...Oops, will probably get a rude message back that is deserved :)  Sorry Henning...

Edited by Mclaneinc
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