HP 32SII success and woes

[jebem]

(02-14-2015 04:44 AM)Sanjeev Visvanatha Wrote:  Then, I removed the PCB and LCD from the 10B, and transplanted the PCB and LCD from the 32SII into the 10B front body.

I now conclude that that something on the PCB is to blame. I used a magnifying glass to carefully examine all traces, the pins for the IC and did not see anything wrong.

Hi, Sanjeev ,
Thank you for sharing your experience with your new HP-32SII.

I have two working HP-32SIi, so I'm not in the mood to open them, considering the fact that the process will destroy the original integrity.
But I'm curious about the machine internals...

So, may I ask you some additional information?

- Did the LCD display came out easily along with the zebra strips?

- Can you identify a small component in the lower left corner, close to the spring contact? From this site, it looks like a smd resistor.

Additional information:
I found excellent Lyuka article showing details here. It looks like the smd resistor is a jumper after all (value=000). Can someone confirm this?


You and others here have done a excellent differential diagnosis, and apparently the possible root causes are now:

- The PCA copper shield is not electrical connected to one of the 6 twisting metal clips as it should. This is MOS technology, and this machine uses large amounts of metal plates that must be grounded to minimize electrostatic fields that can interfere with the SoC (system on a Chip).

- The PCA itself. Well, from the available photos, one can see only 3 components: the NEC SoC, a smd 10uF 16VDC Tantalum capacitor, and a smd resistor.
I would start by replacing the capacitor and then replace the resistor.

Now, the real challenge here is to find out the correct value of it.
Can you identity the printed numbers on it?
Also, if you have access to a multimeter, please try to measure it in circuit; take two readings, first using positive probe on the left side of the resistor, second reading using the positive probe on the right side.
(of course all this must be done after removing the batteries and short-circuiting the 10uF capacitor for at lest 1 minute).

EDIT:
if you get a infinite or a very high reading, most probably the resistor is in open circuit. From what I can see in the photos, this resistor is connected to the ground spring connector.
If this is true (you may check this with a multimeter), that can very well explain the issue.
In that case, I would carefully add an additional 10Kohm resistor in parallel with the smd resistor, by soldering it to the existing smd resistor terminals.
This is a tricky operation, requiring a steady hand a proper soldering iron for this kind of work.

Thank you!