On Tue, 13 May 2008 01:57:41 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

Franc Zabkar wrote:
**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

Oye-- How dumb is that!!! So this is just a step-down transformer!! I thought
all the bricks were AC to DC. Do you think using 12v DC could have hurt the
board? Or that it could be the source of my problems???

As Sam has said, DC won't hurt your tablet. Using DC instead of AC
means that some negative voltages are not able to be generated within
the tablet for important functions such as the serial port and for
your signal amplifiers (op-amps).

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

I also saw at p. 40 of the UG that there are THREE MG3TEST diagnostic tests:
RAM, X-axis, and Y-axis--perhaps corresponding to the 3 tones??? Or not! If
so tho, might suggest Y-axis circuitry.

I suspect that the power-up sequence starts with a basic digital test,
ie ROM/RAM/CPU check, after which the first tone is output. Then
perhaps the next level of circuitry is tested (eg the 2651 serial
controller chip), resulting in a second tone. The next and final set
of tests may involve the analogue circuitry, ie the X & Y wires, which
would fail in this case because of the missing -12V rail. But that's
just a WAG ...

- Franc Zabkar
--
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