Sharp PC-1403H stuck on "BUSY"

[Dave Britten]

I know we've got some Sharp fans here, so I figure it's worth asking. I acquired a PC-1403H that's in very nice condition, apart from the fact that it doesn't seem to work! When I insert new batteries and power it on, it just displays the "BUSY" indicator and can't be turned off again unless I turn off the power switch and press the All Reset button on the back.

I opened it up and replaced the lone electrolytic capacitor and cleaned the power switch contacts, but that didn't seem to change anything. Anything else I should check? Does this model have a self-test feature?

[Didier Lachieze]

This looks like a memory issue. I would check the memory chip to see if there is any bad solder joint.

[david sanz]

(01-27-2022 04:05 AM)Didier Lachieze Wrote:  This looks like a memory issue. I would check the memory chip to see if there is any bad solder joint.

Same problem here with a PC-1403

Thanks for the tip.

Funny thing is machine is unresponsive to ON/OFF switch position. Remains BUSY even if tab in OFF position. Reset buttom does not help. Switches off when Reset pressed, but return to BUSY when Reset released. No obvious corrosion/dirt on board.

Anyway, a nice looking machine. I do not think I would make much use of it, even if it worked.

edit: vendor claimed issue arised after a battery replacement. Perharps pressure on board during replacement set lose the chip ?

good luck, Dave. If you are lucky, maybe I will

[Dave Britten]

(01-27-2022 12:46 PM)david sanz Wrote:  

(01-27-2022 04:05 AM)Didier Lachieze Wrote:  This looks like a memory issue. I would check the memory chip to see if there is any bad solder joint.

Same problem here with a PC-1403

Thanks for the tip.

Funny thing is machine is unresponsive to ON/OFF switch position. Remains BUSY even if tab in OFF position. Reset buttom does not help. Switches off when Reset pressed, but return to BUSY when Reset released. No obvious corrosion/dirt on board.

Anyway, a nice looking machine. I do not think I would make much use of it, even if it worked.

Sounds like about the same issue as mine. I can turn if off if I switch it off and then press the Reset button, but attempting to hit Reset while it's in the on position has the behavior your describe.

I'll have to give it another look with the magnifier and see if I can find any iffy looking solder joints.

[Dave Britten]

Well, a quick reflow of all the chip pins didn't change the symptoms at all, so I may be dealing with either a damaged trace, or a failed chip. I'll need a microscope to troubleshoot traces, and I'm not sure a failed chip could be easily addressed, unless it's just the SRAM chip.