HP 32SII success and woes

[Sanjeev Visvanatha]

(02-16-2015 09:36 AM)jebem Wrote:  ...

So, may I ask you some additional information?

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

-Yes, the zebra strips come out very easily. I used some plastic pliers to carefully remove them.

-The method I used to remove the LCD was to push it from the front of the calculator to the back of the calculator. You do this with the PCB and zebra strips removed. It is held in with a strip of 2 sided tape on the top and bottom edges. If you apply even force, it will start to tear, and you hear the adhesive coming apart. When doing this, be very careful to apply opposite pressure at the right places to the frame of the unit so as to avoid any permanent deformation of the front face.

(02-16-2015 09:36 AM)jebem Wrote:  - 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?

-My unit has the PCB back in place, and I am not sure how many more attempts I will have to untwist them. I did see both of these links in my research. I do not believe that the small SMD component next to the spring contact had any marking on it.

(02-16-2015 09:36 AM)jebem Wrote:  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).

- I can confirm that the electrical contact between twistees and the ground shield is there.

(02-16-2015 09:36 AM)jebem Wrote:  - 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!

- I will have to remove the PCB again to do this. Soldering in new resistor as suggested may be difficult for me to do, as I am not very good at that type of work. I can make the checks and then report back, including noting any markings I see.