Service Manual for Epson scanner?

And no, eserviceinfo doesn't have it.

It isn't here somewhere?

What's wrong with the scanner? I've fixed a whole lot of stuff over the last 20 years or so and had a service manual maybe 0.5% of the time. It helps, but most faults can be found without one. Even service manuals for a lot of things don't go down to the actual component level. 90% of the faults I see are either bad electrolytic capacitors or cracked solder joints.

It's not troubleshooting I need the manual for. I think I know what the cause is. (I posted the question re. this scanner elsewhere in this group earlier. It's copied below.)

If the diagnosis is right (so says the Epson tech) I want to replace the flat bed glass. And there's some kind of calibration afterward. At least that's what I want to find out in the manual.

Thanks.

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Epson Perfection 1640SU Office scanner with Auto Doc Feeder (ADF). The ADF plugs into the back of the scanner via a DIN-8 plug. (The ADF is model EU-34, pn B813222.)

The scanner will scan documents on the flat bed glass with no problems.

When the ADF is used, the paper feeds through the rollers smoothly. No jams or other feed problems.

The resulting scan in ADF mode is all vertical lines. I tried different resolutions and other settings. Also tried different applications. Same results.

A tech at a local Epson authorized repair facility said that this is a common failure. There is a calibration strip at the "home" position on the bottom side of the flat bed glass. Over time this white strip changes (it shrinks?) and when calibration is done at power-on, incorrect calibration results.

The Epson tech says that this is a quite common failure mode and he does many of these repairs on several different models. (I didn't ask if it was common to other than Epson.)

How does this calibration work such that it succeeds for flat bed scans but fails for ADF scans? Can someone explain?

Thanks.

The 'service manual' for a scanner is ... not much. Cleaning the glass and maybe dusting the optics and especially the reference surface (this is a black or white strip against which the scanner is calibrated at startup) is about all the 'maintenance' there is, except for lamp replacements and wallwart swaps.

You don't need the manual to replace a dead lamp.

If the scanner needs more than that, you throw it away and buy another.

Ye would think that. However I found the service manual for my LED based Canon N650U scanner (free at fixdevice.com) incredibly detailed on operation theory with 110 pages, for something that contains very few parts, and not even a power supply (USB powered).