Power Supply PCB for Nikon Coolscan LS-40, LS-4000, LS-50, and LS-5000 scanners: repair and notes.
Power Supply PCB for Nikon Coolscan LS-40, LS-4000, LS-50, and LS-5000 scanners are switching power supplies with 3 outputs: +5V, -12.2V, and +15.5V (+/- 5% tolerance). The power supply for all these scanners have the same ratings and dimensions and are interchangeable.
Two most common problems with these power supplies are:
1. One simple but fairly common failure is when the power switch stops latching in ON position. The scanner can be powered ON and operated but you have to keep the power button pressed by hand. Not a good way to scan. The power switch is ALPS SDL1P-D manufactured in Japan and sometimes you can find it on Ali Express and other second-hand retail sites, just google "ALPS SDL1P-D switch tip foot". It can be replaced fairly straightforwardly if you have a proper soldering iron. It is easier to remove the faulty switch if you first cut the metal support stays on its side using dremel cut-off tool - then you only need to de-solder two feet.
2. Another frequent problem (in the power supplies manufactured by SANSHIN, I had only seen this in LS-50 and LS-5000 units with serial number 4XXXXX) is a bad control IC in the inverter section, the part STRW6756 manufactured by Sanken. The replacement is also straightforward. Location of STRW675 (it is screwed to thr heatsink) is indicated by the red arrow below:
I had those replaced in a few units and they all came back to life. The IC is not expensive, just google "Sanken STRW6756", it looks like this:
For more serious repairs I had to look for an expert. I had seen people on e-bay offering diagnostics at $50 and then repair at $500. This seems excessive. I had found this company:
Power-Medic
1442 E. Lincoln Ave.
Orange, CA 92865
I had once had a supply I could not repair myself. Dave from Power-Medic had repaired the supply in 2 weeks for under $100 including shipping. I would highly recommend him (I do not have any business arrangement with him :)).