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HP 41 Eramco RSU-2 - help, please!
07-26-2016, 02:38 PM
Post: #1
HP 41 Eramco RSU-2 - help, please!
Recently I acquired a rare Eramco RSU-2 softselect rambox for the HP 41.
I received it empty (with "no roms" in all pages), what at first sight was no surprise, since the lithium battery was dead after all these years. I replaced it, but unfortunately I can't make the box run again.
I tried out all the steps described in the very good and detailed forum articles, written by Peter and Diego, using a clonix41 module equipped with Peter's INITRSU image, without success.

My RSU-2 differs from the version pictured in the mentioned articles in an important aspect:
It does not feature the two external dip switches for read-disabling the box and write-protecting pages E and F ( where the operating system of the box must be loaded ).
Instead, it has one dip switch inside the box; maybe it is an earlier version or a prototype.
Of course I have no documentation and don't know what this switch does. I assume it is for read-disabling, because without such a feature desaster recovery would not be possible at all.

When I tested the box with the switch in the position when I received it, any write commands ( COPYP, copying pages from the Clonix41 to the Eramco ram pages) simply are ignored, empty pages remain empty. ( I get the result "NO ROM" when doing a CAT 8 through F ).
After setting the dip switch to its right position and turning on the calculator on again, the calculator freezes immediately, due to garbage in the pages, or a defective hardware.
When I return to "dip-switch-left" mode and do a "CLRSUA" from Peter's INITRSU module which should set to zero every single bit in all 4 banks of the RSU, the result is the same. The write commands ( which should work even in a read-disabled mode! ) seem not to work at all.
I guess it is a hardware fault, and I don't know what to do.
It would be a pity to throw away such a rare device.
Is anyone out there who would try to repair it?
I am ready to pay for a repair attempt without any guarantee of success, of course.
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