38E: dot in upper left corner of display

[Dave Britten]

(01-21-2020 01:50 PM)burkhard Wrote:  I have a really nice looking 34C with the same problem. Even with freshly-charged batteries which run my other Spice models fine, this one keeps the low battery light on. In my case, I suspect the problem is how it was treated by the guy I bought it from: He "checked it out" by powering it by jumpering a 9V battery up to the battery contacts. Why would someone think 9V is close to 2.4V? Ugh.

Anyhow, it did not blow the ACT chip, because otherwise it works fine, but it does have that low battery light stuck on. If someone understands how the voltage sense circuit, that is probably the place to scour around. With a lot of other projects on the plate, it has been low on my list of priorities. Perhaps we have the same issue?

It sure sounds like the same issue, but it's hard to say for sure without being able to easily test the voltage at the PCB pads, and the resistance between those pads and the battery terminals. It seems to work fine otherwise, though I don't know yet if it will give out at a higher voltage than it would normally. I should probably just key in the 12C benchmark program and let it run, then check the voltage when the display shuts off.

EDIT: I popped in a reasonably fresh NiCd pack rated for 1000 mAH, typed in the 12C n-queens benchmark program, and it's been happily running for about 36 minutes now, with the low-battery dot illuminated the whole time. I'm not 100% sure the program will produce the same/correct results on the 38 - STO Nj isn't a valid operation, so I replaced it with just Nj. When I compared the two functions on my 12C, I couldn't see any obvious difference between them. I'll report back when it either finishes or runs out of gas...