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Houston Tech HT12888A Real Time - battery hack

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First post, by Nexxen

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I bought a motherboard with a dead RTC battery, and it would not store any change except for date and time.
M/b is a rebranded (?) PcChips M530 (that is for sure as the BIOS matches + pics are identical).

After researching on the internet I came up with nothing.
But, after close observation, I noticed that I could see the chip's pins (with 0.45V) and finding that it is in fact a plastic cap (with a rebrand markings) on top of a VIA VT82885N, plus a BR1225 battery soldered the the legs of pins 4 and 8.
The cap can be easily removed with a screwdriver on aither of the short sides.

As with the Dallas battery hack pins 4 (-) and 8 (+) you just solder a CR2032 on it and you are good to go.
In the original PcChips pics the RTC is a Dallas, making unsure if it is actually compatible with any of those RTC or just Via, but see note at the bottom.

Note: user alexanrs posted:
Re: Bought these (retro) hardware today

Basically if a Via 82885N works than a 82887 should work too; Dallas could be an option if no Via chip is available.

PC#1 Pentium 233 MMX - 98SE
PC#2 PIII-1Ghz - 98SE/W2K

Reply 2 of 8, by Nexxen

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CapitanOdessa wrote on 2020-05-05, 16:55:

Weird, I have two of those motherboards, and both of them have a CR2032 battery under a cap that says HT12888B. I could send a photo later.

That was my case, lift the cap, and a battery is soldered to two pins. But it was like 8-10mm in diameter (like a 1/3 of an inch).
In conclusion, the HT1288A is not an exclusive chip, it can be replaced. Just don't know if a VIA chip could do the same.

Old stuff with obscure blueprints 😀 Nice era.

Yes, send pics! I forgot to put mine.

PC#1 Pentium 233 MMX - 98SE
PC#2 PIII-1Ghz - 98SE/W2K

Reply 3 of 8, by CapitanOdessa

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Hello! I'm truly sorry I didn't answer any faster! When I had the time, I spent it doing something else and completely forgot. Here are the pics! I think the HT12888A is just the clock manager, and the HT12888B handles the power, I need to give it a try and boot it again whenever I have the time.
With cap
TMs03Bm.jpg
With no cap
qodxZzm.jpg

Reply 5 of 8, by Nexxen

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Pics

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PC#1 Pentium 233 MMX - 98SE
PC#2 PIII-1Ghz - 98SE/W2K

Reply 6 of 8, by Nexxen

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Pics again.

Will post pics of the battery soldered with a lousy job by me.

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PC#1 Pentium 233 MMX - 98SE
PC#2 PIII-1Ghz - 98SE/W2K

Reply 7 of 8, by rwrgn

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This thread was crucial in reviving my old P166 motherboard. Never would I have guessed to pry the HT12888A cap open and find a battery inside.

I did not manage to fit a CR2032 on top of the chip neatly, so I went with a CR1220 instead, in line with the original battery.

i58BB4E.jpeg

Not too beautiful a result of soldering, super glue, electrical tape and heat-shrink tubing, but it works!

Reply 8 of 8, by Nexxen

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Glad I could help. Nice work, neat and easy. Sometimes the not so cute is good if it is 100% functional.
I was a noob back then, an educated noob now. The beauty of this place is the help you can get.

PC#1 Pentium 233 MMX - 98SE
PC#2 PIII-1Ghz - 98SE/W2K

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