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HP 50g & SD Cards: Performance, Format, Notes
09-02-2016, 11:27 PM (This post was last modified: 09-06-2016 10:28 PM by JDW.)
Post: #82
RE: HP 50g & SD Cards: Performance, Format, Notes
Here is "part 1" of a 1080p 60fps video I made of OPENING and REPAIRING the 50g:

Sept.7 Update: I replaced the above YouTube video with the full version showing the jumper wire repair.

There is no Part II yet because as you see at the end of the video, I really need either (a) a schematic of the calculator or (b) a diagram of that exact same SD Card Slot Mechanism in order to complete repair. If a kind soul among you can provide me with such information (PM me if you like), I will complete attempt to complete the repair in a second video, then merge the two and upload the unified video on YouTube. That is why I left the current video unlisted for now, since I may delete it if I ever make a unified video showing that last part on how to fix it.

Be sure to watch the video in full screen mode, especially on a larger screen device, to see the PCB in its full glory, seeing more clearly the points I desoldered and tested.

Once again, the repair objective is to fix whatever problem exist in the 50g that is making it falsely believe SD cards are Locked (when in fact they are not). Whatever kind assistance any of you could provide would be greatly appreciated.

Thank you.

UPDATE: I've been spending the last couple hours viewing diagram after diagram on SD Card Sockets (connectors). There is not standard for the CD (Card Detect) and WP (Write Protect) pin-outs from what I can see. But most tend to put the WP output on the far edge of the card, which if you watch my video above would appear to be the line connected to resistor R66. But as you see in my video, my test seems to indicate that the R66 line is actually CD. The reason I think that is because when I removed R66 and tested, you can see in my video that when I push the FORMA button nothing happens and when I refresh the card (Slot 3) vanishes in the File Manager. However, when I subsequently removed resistor R68, with R66 attached, the card was detected (although I still got a write protect error).

I really need a datasheets on that exact SD Card Socket to know for sure, but as you can see in my video, it certainly seems that the WP output is the PCB trace attached to resistor R68.

The thing is, I have been reading a lot of SD Card Socket datasheets and all of them say the same thing regarding how WP is output. In every case, all the datasheets say that the WP output is Grounded when the card is NOT protected (not Locked). And they say the WP output is Open Circuit when the card is protected.

But if you watch my video, you will see that I used a Fluke meter set to Continuity Check and then touched one probe to the pad associated with R68 and then touched the other probe to the metal frame of the SD card socket. I must assume that the metal frame is always grounded. If so, and if R68 truly is WP, then such would seem to show that WP is being grounded properly. And if "WP OFF" truly is defined by "WP = GND" then why would my 50g complain about the card being write protected all the time?

Also note in my video that even after I remove resistor R68 (which again, I assume is the WP line, although I could be wrong), the card was detected by the 50g but I got the same Write Protect error as always. Any thoughts on this?

Again, if anyone can direct me to a schematic on the exact SD Card Socket used in the 50g, and if any beautiful soul out there has a full schematic on the 50g, please let me know. Regardless, I would appreciate hearing your thoughts. Thanks.
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RE: HP 50g & SD Cards: Performance, Format, Notes - JDW - 09-02-2016 11:27 PM

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