Yet another A3000 battery leak cleanup thread

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IanJeffray
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Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

Boring! Oh well. Here we are anyway :)

Bought with known faults but unseem. Whip off the lid and keyboard... Initial impression is ok:
IMG_8116.JPG
...zoom .... enhance ... ah there's the rot we expected:
IMG_8118.JPG
Pull and flip the board. Yep it's not 'light'...
IMG_8120.JPG
May need to swap-out this gunky mouse socket:
IMG_8124.JPG
And definitely need to change these nasty ROM sockets (note the fully knackered contact on ROM4).
IMG_8127.JPG
So it's off with her head... byebye ROM sockets, Keyboard connectors and RTC.
IMG_8129.JPG
That'll do for today. Tomorrow, we rebuild! :D
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IanJeffray
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

Other mildly interesting things about this basic machine - a 2MB/4MB RAM card with socketed ZIP chips. What part do I need to swap this for 4MB? :)
IMG_E8130.JPG
IMG_8131.JPG
And I notice all the main ICs are -10QC parts, except VIDC which is a -12QC. That's unusual, I think. This is an issue 3 board, so these faster parts would have been coming on for A540/A3010 Adelaide, but kind of wasted in this machine really. (And the -10QC MEMC is not "Blue blobbed" btw)
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Re: Yet another A3000 battery leak cleanup thread

Post by thecellartroll »

These threads are never boring. I've learned loads of stuff about how these machines actually work from peoples battery damage threads.
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IanJeffray
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

I wrote:
Wed Nov 24, 2021 3:39 pm
Other mildly interesting things about this basic machine - a 2MB/4MB RAM card with socketed ZIP chips. What part do I need to swap this for 4MB? :)
8x TMS44400A would do the job, according to Chris' Acorns. :) Now to find a buyable equivalent!
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IanJeffray
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

Tomorrow? Meh. Another couple of hours, cleanup, checks, fit new keyboard connectors, ROM sockets, CMOS socket and brand new CMOS chip (old one was toast). Add some pins for the offboard battery. Add new RO3 ROMs. And she booots!

All basic functions seem ok, including the keyboard and mouse (despite the grotty socket - gave it some cleaning).

Well that was a bit too easy. :)
IMG_8133.JPG
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baz4096
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Re: Yet another A3000 battery leak cleanup thread

Post by baz4096 »

No traces to fix at all? You're making it look too easy Ian :D
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

baz4096 wrote:
Thu Nov 25, 2021 12:06 am
No traces to fix at all? You're making it look too easy Ian :D
Well, there probably would have been tracks to "fix" but I seem to have caught this one just at a good point before the rot set in -- here's a stripped-down photo during rework - you'll see a LOT of tracks that I've stripped off the resist and covered with solder (note all the wee ones between each ROM pin!) -- all these spots, the battery had eaten in to and lifted the solder resist, but not bad enough to destroy all the copper - so this was a preventative measure to remove the rot and prevent it going further.

But yes, this is actually the cleanest A3000 I've worked on, actually - lucky.
IMG_8132.JPG
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

So it turned out that the CMOS wasn't holding. It had 5V during normal power-up, but no battery supply. There was a hairline crack on the annular ring feeding the bacttery voltage - enough that it buzzed-out, but not enough to pass juice to hold the CMOS properly. One strip-down-add-patch-wire-rebuild later, and that's fixed.
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Re: Yet another A3000 battery leak cleanup thread

Post by kppot »

Very interesting as usual
What is the p/n for keyboard connector, or was it just NOS part?
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Re: Yet another A3000 battery leak cleanup thread

Post by IanJeffray »

kppot wrote:
Fri Nov 26, 2021 8:25 pm
What is the p/n for keyboard connector, or was it just NOS part?
It's a TE 7-520355-0 . https://www.mouser.co.uk/ProductDetail/571-7-520355-0

I had been under the impression a suitable part was now unavailable, and had been putting Amphenol "Clincher" connectors on the FFC -- and that's still a good idea when the FFC is very damaged -- but this part fits perfectly, and whilst the contacts are staggered, compared to in a line as per the original, it works just fine - the contact patches on the A30x0 are decently long and, even, in this case, where it had a rotted end, I snipped off about 2mm from the end of the FFC and it's perfectly fine.
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