Stan Nagrod reports that removing R11 from his computer cured his loading problems. I had tried this on mine, and found no discernable difference (from the computer’s standpoint, it shouldn’t have any effect). Presumably, this is a function of the recorder rather than the computer. (You can’t hurt anything by trying it.)
On that subject, the LOAD AMP (SWN 2/5 pg. 8) cannot harm your SCLD. Its design limits the output swing to well within the limits specified by Timex. If anything, LOAD AMP will help protect against excessive input voltage. You could add a reverse diode to the clamp at the input of the SCLD, but then the maximum voltage swing at the SCLD input is only about 1.8 volts, and you’d be defeating the whole purpose of getting more signal to its input.
I heard from several users who, like me, have more trouble with loading after the machine warms up. LOAD AMP cured this in every case.
I’m not supplying LOAD AMPS anymore; instead, I encourage user groups to have a local hardware hacker build them up for anyone who needs one. If anyone out there wants to build them for general sale, go for it. Consider this a release to public domain.