Dallas 1287 RTC Restoration

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Dallas 1287 RTC Restoration

Postby Yuuki47 on Thu May 02, 2019 5:16 am

Hello everyone, i've come here for some advice

So... I recently got a vintage machine from somewhere around the late 80s, although it boots and everything, it's actually
quite useless because it forgets CMOS values everytime it restarts (even if it's plugged on) and upon opening it up to locate the CMOS battery, it was nowhere

So I found out that the CMOS battery was nowhere because... it is actually inside the RTC IC! (Why Engineers??!?!? Why?!?!) but to my luck, it is actually possible dig to the chip and expose some battery contacts, which I did and it worked BUT big catch, how safe is that actually? I'm essentially rewiring a new battery to the CHIP and also to the old battery because it's still connected and i dont really see a way to get rid of that old rundown battery that we dont even have an idea of what its made of, I don't really fancy fires or explosions so has anyone here actually done this and had no bad things happen long term?

I say this mod worked, it appeared to but the laptop's charger decided to randomly die on me RIGHT after i did the mod, but it most likely did indeed work because i didnt complain about invalid configurations on CMOS, it just complained about system disks
Yuuki47
 
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Re: Dallas 1287 RTC Restoration

Postby ZL2AOX on Thu May 02, 2019 12:57 pm

I would suggest removing the original DS1287 entirely and replacing it with a newer DS12887.
Monotech sells something suitable.
ZL2AOX
 
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Re: Dallas 1287 RTC Restoration

Postby Yuuki47 on Fri May 03, 2019 8:38 am

Wow I had no idea this was even a thing, or rather I didn't expect people to make that replacement, any tips on desoldering the chip? I already tried sucking away all the solder, but for some reason it just won't budge, it's as if there is still solder under it, rather through the holes, although it's weird for the board to have a combination of SMD and THT on the same component, or maybe it's glued? I just can't tell, but im positive 100% that I removed solder on the THT pins atleast, and it simply won't even move an inch, I had to dig out battery contacts when the chip was on the board for god's sake XD
Yuuki47
 
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Re: Dallas 1287 RTC Restoration

Postby ZL2AOX on Fri May 03, 2019 12:27 pm

I would say it's unlikely to be glued in the original assembly, though it's possible someone later used glue when carrying out a replacement. More likely it's still being held by residual solder. You may need to resolder one or more pins so there's sufficient solder to conduct heat into the joint when desoldering. Caution is needed, as there's a risk of the solder pads lifting off the board if too much heat is applied! Not sure what tool you're using but if you haven't attempted this sort of work before, it's a good idea to practice desoldering on some junk boards first.
ZL2AOX
 
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