PLCC SOCKETS ARE EVIL

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IngoQ
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Re: PLCC SOCKETS ARE EVIL

Post by IngoQ » Wed Dec 27, 2017 10:31 pm

Do you mean these measuremnts here in the data sheet?

http://www.precidip.com/AppHost/9699,1/ ... XXX-24-008
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Wed Dec 27, 2017 10:42 pm

IngoQ wrote:
Wed Dec 27, 2017 10:31 pm
Do you mean these measuremnts here in the data sheet?

http://www.precidip.com/AppHost/9699,1/ ... XXX-24-008

No.. the dimensions of the spacer parts...

1.jpg
1.jpg (40.83 KiB) Viewed 528 times
.. But these look the same as the sockets I have now with how they look on the drawing anyway.. but think the ones I have are 3M.
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Re: PLCC SOCKETS ARE EVIL

Post by IngoQ » Thu Dec 28, 2017 10:36 am

I made some photos of mine, with and without cpu. Maybe these help?
plcc_1.jpg
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plcc_2.jpg
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plcc_3.jpg
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plcc_4.jpg
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plcc_5.jpg
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plcc_6.jpg
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plcc_7.jpg
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plcc_8.jpg
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plcc_9.jpg
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Last edited by IngoQ on Thu Dec 28, 2017 10:46 am, edited 1 time in total.
Reason: Forgot one...
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Thu Dec 28, 2017 11:06 am

IngoQ wrote:
Thu Dec 28, 2017 10:36 am
I made some photos of mine, with and without cpu. Maybe these help?
Thanks, the sockets I have are not brown, I don't suppose you have a 68HC000 CPU to try in the socket, its the type I would ship with the STE booster..
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IngoQ
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Re: PLCC SOCKETS ARE EVIL

Post by IngoQ » Thu Dec 28, 2017 11:56 am

exxos wrote:
Thu Dec 28, 2017 11:06 am
I don't suppose you have a 68HC000 CPU to try in the socket, its the type I would ship with the STE booster..
I do :)
plcc_hc_1.jpg
plcc_hc_1.jpg (695.48 KiB) Viewed 513 times
plcc_hc_2.jpg
plcc_hc_2.jpg (483.72 KiB) Viewed 513 times
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Thu Dec 28, 2017 11:59 am

Thanks, bit difficult to tell, but it looks like the spaces in between the pins are not going in as far as it did with the original CPU ?
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Re: PLCC SOCKETS ARE EVIL

Post by IngoQ » Thu Dec 28, 2017 12:36 pm

There seems to be a tiny gap on two sides of both of the CPUs, but it's only a fraction of a millimetre, and it is slightly varying from side to side and CPU to CPU. Could be due to tolerances or how I inserted them...

But it looks like they are still making a good connection, as far as I can tell... I have no microscope to get any closer, sorry.
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Thu Dec 28, 2017 12:43 pm

IngoQ wrote:
Thu Dec 28, 2017 12:36 pm
There seems to be a tiny gap on two sides of both of the CPUs, but it's only a fraction of a millimetre, and it is slightly varying from side to side and CPU to CPU. Could be due to tolerances or how I inserted them...

But it looks like they are still making a good connection, as far as I can tell... I have no microscope to get any closer, sorry.
No worries :) hopefully my sockets will be here tomorrow so I can investigate them further :)

Does concern me about other PLCC chips and sockets, such as the larger PLCC PLD's I starting to use also. I think it only takes a slight tolerance on the chipboard socket and they do not make good connection.. It actually makes sense as I am sure I have had issues with other PLCC and chips like the ROMs in the past and even on my development board I did a couple years ago which uses PLCC sockets, where I seem to have some odd contact issues on there at some point also.
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Fri Dec 29, 2017 2:13 pm

So the new precidip arrived and I did some comparisons...

hc2.jpg
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This is the HC CPU with the new sockets.. It looks like the spaces in between the IC pins go in a lot further.. Or they could simply just be longer than my other sockets..

hcold.jpg
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This is the HC CPU with my old sockets.. The plastic spaces do not really seem to go in between the IC pins.. The contact connections do look good though..

ttl.jpg
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This is the older TTL CPU with the new sockets. The spaces seem to fit nicely between the IC pins..


hcold2.jpg
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This is the HC CPU in the old sockets, it looks like the contacts are not connecting..


hcnew.jpg
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The HC CPU with the new sockets, it also looks like the contacts not meeting. But this could just be the angle of the pins it is difficult to say..


ttlnew.jpg
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This is the TTL CPU with the new sockets...


With the new sockets and the TTL CPU, looking all the way around the contacts I think they look okay overall..

With the old sockets and the TTL CPU, looking all the way around, does generally seem to look okay overall as well. Generally I have not had any problems with older TTL CPUs and sockets..

With the HC CPU and the new sockets, the gap between contacts looks larger, but it only looks like one side of the chip is making bad contact. But again I cannot say 100% as it could just be the angles of the pins making it look like there is a gap..

With the HC CPU and the whole sockets, pretty much looks like the new sockets, where there seems to be larger on some Pins but Not on Others.

I took the dimensions of both chips, was not really seem to be much, possible the HC pins overall have been squashed in some point.

HC dimentions
25.22mm x 25.03mm pins
24.32mm x 24.30mm case

TTL dimentions
25.10mm 25.14mm pins
24.33mm x 24.29mm case

Just for the record, during all testing sockets and chips, have gone round each pin on the socket on bent them outwards a lot, I have also been around the CPU is and bent the pins out as well and it did not make any difference. I also inserted small header pins which are used on my man upgrades to push the contacts out further in the sockets and this did not change anything either .So really it should be no reason for any bad contacts.

Overall, I am still no further forward with this I think. The HC CPU does not seem to fit correctly on new or old sockets. I have tried a couple of HC CPU is as well and they do look dodgy.

Going by the images and looking under the microscope, it just looks saying that the HC CPU for some reason does not make good contact in the sockets.

From what I can tell the precidip sockets do look like they fit more snug around the CPU. Though I cannot see any real differences in contacts between the precidip sockets and my original sockets.

One thing which is still in question, is that re-soldering IC sockets always seem to make things worse. It is possible that as the pins are heated up during soldering, maybe the plastic of the self distorts somehow causing the bad connections. It is even possible that the pins themselves could warp during soldering. Of course the sockets I photographed were both on unused sockets.

Only thing left is to physically try the new sockets in my booster board and see if they actually work or not...

EDIT:
IMG_2145.JPG
IMG_2145.JPG (59.14 KiB) Viewed 496 times
Quickly made up a new test board with a precidip socket.. Similar as before, the TTL CPU works, but the HC one does not.. I know the HC CPU's work I tried a few of them is to be sure. Then put back the TTL CPU and it worked again.

When I had the plug-in STE booster looked into the socket ( see here viewtopic.php?f=6&t=353&p=3164#p3128) , there was nothing on the board to interfere with anything (I even removed the GAL and wire linked over it to connect the CPU clock again .. ), it was just literally the CPU soldered onto the board going directly to the header pins which were pushed into the PLCC socket. So it proves the HC CPU can work with this booster board at least. They could possibly be like 1pF capacitance between the CPU pins due to the extra length, but I really do not think that will change anything. If that was the case, then the ST would surely try to at least boot up and just crash randomly. But the machine just simply acts like the CPU is not plugged in at all.

As said before, inserting the pins into the CPU socket alone with the HC CPU also did not work. I really have a hard time to believe the contacts were just bad during all these tests which I have done but it is the only conclusion I can come to.

Of course a sockets may not be directly to blame, it could just be some bad manufacturing tolerances on the CPU itself. But either way, the HC CPU and the sockets just do not work together..

I tried to track down the original sockets I use but they seem to not exist any more. I never had any issues with the sockets I purchase a long time ago. It was only on recent purchases of sockets I started to see this trouble.

I still basically am suspicious of the plastic spaces in between the pins, it was the only real difference I could see between my original sockets and the new sockets. I can only really assume the plastic parts are pushing the pins away from the contacts when the CPU is inserted. Then would think bending the pins upwards on the socket and inserting pins into the socket pins further would work.. Seems not.

Maybe there is something I am totally missing in all this, but I do not really see what :shrug: I think all future projects just not use the PLCC sockets. It is a little unavoidable for the ROM IC's currently, but so far I do not seem to have run into problems like this with those yet.

So overall I am still at a total loss really :stars: :pullhair: :shrug: :shrug:
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Re: PLCC SOCKETS ARE EVIL

Post by exxos » Thu Jun 14, 2018 11:33 am

In light of wanting to add a socket onto the new DUALTOS boards, and needing a low profile, I had a look at SMT sockets this time..

I ordered them from Farnell, the images on the site were actually wrong, no surprise there, and there was only actually 2 different sockets. As usual, different manufacturers putting their name on the same generic product and charging various prices as well! :roll:

First socket, I'm just going to say un-branded ...
2.JPG
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Second socket is a 3M...
1.jpg
1.jpg (194.3 KiB) Viewed 73 times

Now the interesting thing is, both contacts on both sockets do actually seem to look good overall, which makes a change!

3M branded socket however has the plastic "spacers" which I was going to call them, which go in between the pins of the chip. I think this is where half the problems start.. As the chips themselves seem to vary a lot on the contacts width, those plastic spaces can actually push the chip contacts away the socket contacts. This is being one of the main problems that I have seen with normal sockets.. So I'm basically calling that a bad socket, simply because of that one issue.

Now the 3M socket is a lot more interesting.. Firstly the plastic spaces are not as long and actually stop before they get to the contacts. So there is basically no problem there of spacers pushing away the chip contacts.

Secondly, the spacers are also reinforced with some additional plastic which can be seen running top to bottom of the image. I think that is also very good feature to have. In particular when trying to remove chips from sockets, they rarely come out straight and end up getting twisted little which I think is part of the problem of the sockets getting damaged. As the sockets are reinforced, these should withstand a lot more abuse than other sockets.

The contacts themselves also seem to connect extremely well looking at the images. So currently this seems to be the only socket I have found it actually seems to be decently constructed!

So I am going to update my DUALTOS board (again!) So I can try one of these sockets on that and see if it is reliable... I have add no crazy issues soldering the ROM and CPU on my test STE boosters, so clearly sockets are all to blame.. So if I will try these sockets and hopefully the issues will not come back with the 3M branded ones...

I will likely purchase a normal PLCC 68 socket 3M brand, and see if similar "features" are added on those sockets as well. Of course it would have been a whole lot easier if distributors and indeed manufacturers actually put a proper images of the sockets up!
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
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