Cmos Battery/Clock

amdx · 2014-12-02T00:51:48+00:00

Well I've received my M48T86PC1 Cmos Clock Lithium Battery as a gift from China, according to the custom declaration. It is an ST microelectronics part, my concern is the manufacturing date. The Chip is labeled as below, M48T86PC1 Real-Time Clock Contains Lithium Cell 990SN VH MYS 99 1033 WO723Y I hate seeing all the 99's, any one know how to read a date code for ST microelectronics. Another route, any chance I could measure the battery voltage? The pinout is here but I don't know if the battery voltage is present on any pin. I wish I would have done a little more research before ordering this chip, I'm now finding a replacement chip DS12887. With chips available from Mouser and Digikey, so I expect recent manufacture. Maybe I'll be lucky and this chip will be found to be recent manufacture. I only want to replace the chip once on the motherboard, a second time might be pressing my luck. I'll order a second newer chip if it seems appropriate. Your help appreciated, Mikek

Cmos Battery/Clock

Dec 02, 2014 23 Replies

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Don Y 11 years ago

Dunno. You also want to do this OUT of the circuit (as you have no idea if those pins are N/C on the motherboard). And, if it confirms the location of the cell, probably cut those legs so they can't connect to the PCB.

(Where are you located?)

Remember, DVM not (analog) VOM. The latter will effectively kill the cell in the time it takes you to measure.

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Don Y 11 years ago

Obviously, you want to screw with the OLD (known bad) chip, first!

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amdx 11 years ago

Ya, I ground into it this morning. I found metal near pin 16 but, I didn't find any metal at a reasonable depth near pin 20. I went deeper than any of the pictures of grinding on the other chips. Over 3/32". It doesn't make a lot of sense because internally there are two compartments, the two pins are not in the same compartment. Pin 20 is right a the seam between the two compartments. I ordered a new chip from Mouser. I'll wait for it before doing any more.

Thanks, Mikek

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amdx 11 years ago

Happy Days,

A recap, I ordered an M48T86PC1 from China and it turned out to be old stock, and the Lithium battery was dead. I received a Dallas DS12887A Cmos Clock Lithium Battery from Mouser as replacement for the M48T86PC1. I installed it and the computer works just fine. Next step, see if the computer will still run the HP 3330B Synthesizer and the HP 3570A Network Analyzer under GPIB control.

Thanks for all the help, Mikek

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