PLCC socket - Adjusting the contacts

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rubber_jonnie
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PLCC socket - Adjusting the contacts

Post by rubber_jonnie »

I spoke to exxos a couple of weeks back with regards to PLCC sockets, and how that over time the metal fingers that make contact with the chip can lose contact causing all sorts of weird problems.

I'd had 2 machines with odd problems that turned out to be loss of contact within the PLCC socket, so decided to work out a way of adjusting the contacts back to their normal position.

First off I made a tool that comprises just a few odds and ends I had lying around:
1. 2x long header pins, about 15-20 mm long.
2. A slim piece of discarded Veroboard.
3. Some insulation tape.

Firstly, you need to create a small hook at the end of one of the header pins. The hook should be just about the last 2-3 mm of the pin, no more, like below:
hook.jpg
hook.jpg (301.44 KiB) Viewed 7211 times
And the other pin remains as it is:
point.jpg
point.jpg (267.44 KiB) Viewed 7211 times
You then solder each pin to a slim piece of vero board, then wrap the veroboard in insulating tape. Now you have your tool.

The completed tool is shown here for scale sitting atop the MMU socket of a 520ST.
scale.jpg
scale.jpg (432.24 KiB) Viewed 7211 times
Here we see the same socket, and it illustrates nicely the sort of problem we're looking to fix.
socket.jpg
socket.jpg (428.73 KiB) Viewed 7211 times
The bottom row of contacts is clearly not well lined up, and likely to cause poor connectivity between the chip and the socket, leaving us with all kinds of problems.

This is where our tool comes in. Using the hook end, you can carefully hook under the bottom of the finger and gently tease it out ats below.
Tweak_hook.jpg
Tweak_hook.jpg (371.43 KiB) Viewed 7211 times
You must be very careful when doing this, as the fingers don't need much to pull them out, and if you go too far, you'll just need to push then back in again.

The other end of the tool can be used to tweak from the top, by either gently pushing on the fingers, or pushing in from behind the fingers as below.
Tweak_point.jpg
Tweak_point.jpg (363.13 KiB) Viewed 7211 times
Again, not much force is needed here to make these adjustments, so take it gently.

Hopefully this will help some of you folks out there who have this problem. It's important to note that you should also really aim to clean the contacts on the chip too before reassembling.

Good luck!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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exxos
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Re: PLCC socket - Adjusting the contacts

Post by exxos »

:bravo: :goodpost:

Here is my tool...

pin.jpg
pin.jpg (41.91 KiB) Viewed 7198 times

Its not every good though as it needs something "flat" to grip onto :roll:
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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rubber_jonnie
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Re: PLCC socket - Adjusting the contacts

Post by rubber_jonnie »

Yeah, pretty much what I'd been using too, but I kept losing it, so decided I'd be better to make something more permanent. And less likely to lose!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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kludge
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Re: PLCC socket - Adjusting the contacts

Post by kludge »

Great tip. I think I'll have to make such a tool!
A kludge is a workaround or quick-and-dirty solution that is clumsy, inelegant, inefficient, difficult to extend and hard to maintain.

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