Posted: Thu Jun 01, 2006 1:35 am Post subject: Viewsonic V1100 CMOS checksum failure message
In 2004, the university that I work for bought 10 Viewsonic V1100 tablet PCs. Within the 12 month warranty period, 5 of them had given CMOS checksum errors at switch-on. The error message as it starts to boot asks the user to press F1 or F2 but this isn't possible unless a keyboard is attached. A temporary fix to boot the PC is to press and hold the power button to turn the power off, start again and then reset the date and time after booting.
The V1100 manual mentions "BIOS problems, CMOS checksum failure message" and recommends contacting Viewsonic Customer Support. It also states that the life of the CMOS battery varies from 3 to 5 years depending on usage. We contacted Viewsonic Customer Support and then sent all 10 tablet PCs back under warranty to have the CMOS backup batteries replaced but we still had problems with CMOS checksum errors at switch-on.
As long as the PC's main battery pack isn't flat, the CMOS backup battery is trickle charged, whether or not the PC is connected to AC power. If the main battery pack runs completely flat or is removed, the CMOS battery can only backup the CMOS and run the clock for a maximum of about 500 hours. After that, the CMOS setup, date and time are lost.
The main Lithium Ion battery seems to run down in about 4 weeks without use and after that, the CMOS backup battery discharges at 80 microamps, which seems rather high. After the main Lithium Ion battery is charged again, the CMOS backup battery pack only trickle charges at 9 - 12 microamps so it takes at least 4000 hours to recharge from flat. As about 5 microamps is probably required just to compensate for the self-discharge of the battery, it probably takes more like 8000 hours to recharge the CMOS backup battery fully from flat.
The CMOS backup battery is inside the cover for the RAM expansion socket. It is a Varta 6 volt 40 mAH nickel metal hydride rechargeable, type 5/V 40H. Ours didn't need replacing, just recharging. We removed it and charged it at 6 mA for 8 hours from a 12 volt DC supply via a 1000 ohm resistor. After replacing it, make sure that the PC's main Lithium Ion battery pack doesn't run flat again.
Thats a bummer! I hope Viewsonic makes up for it with great customer service. I wish I had an answer for you but my knowledge is almost purely limited to issues or topics I have personally delt with (self taught on everything) so I do not. Chris has quite a bit more experience though and may have an answer. In the meantime I would try contacting customer support again and let them know you are still having problems- see what their action would be this time. _________________ [b]James Volodymyr R.[/b]
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