I finally got around and completed the USB IR Toy v3.0 I got from Dangerous Prototypes .
Took me a while, had to go over the BOM, then I realised that I looked at the 3.3v version’s BOM etc., but it’s done.
(I had to bend the UART pins because my pickit wouldn’t fit and I was lazy to look for header extension).
I was just watching an eevblog episode about VIA’s (research for my project), and I saw Dave using Saturn PCB Toolkit for various calculations.
Interestingly (and not surprisingly) the tool is only available for Windows, but I wanted it anyway, so I decided to give it a try under WINE.
It wouldn’t install, throwing a few errors, but then I did manage to install it on my Windows and copy the .exe file over to my mac,
and – voila, the thing works, it should also work on Linux…
First part here
3 days later, my mouser order arrived to Japan (this is super fast), I got the relays, desoldered the bad one (proper desoldering tool is very useful here).
(Right is new replaced, left is the old one for comparison, didn’t take it apart though).
Soldered the replacement and couple of screws later, I had the multimeter repaired, reassembled and ready to test.
(Don’t forget to note colors of the internal cables connected to the rear panel posts)
First I realised that once or twice another test had failed (500.2), and also 600.1 and 601.2 (which was definitely a change from original 600.1,600.2,601.1).
When the test process asks for 4-wire short I literally used a 4-wire kelvin clips shorted, and this seems to be the reason why error 500.1 came up, and likely the 600.x ones now were because I shorted HI to LOW instead of AMPS.
Now, for 4-wire short I used pomona banana leads (I think 12-ich ones) to get as close to a “real” Keithley 4-wire short brace (it’s literally a brace with 4 banana plugs that snaps right into the posts).
After the change of leads – all of the tests succeed. Voila, I repaired the multimeter (but I think I will someday make a a 4-wire short brace for reliable testing).
I got a Keithley 2000 multimeter, and as usual the first thing I did was to test it.
Builtin self-test ran through most of cases without issues but failed with 600.1, 600.2 and 601.1.
With a little research I found out that those errors are related to amps/ohm tests, and a little later I found out that one of the common causes is broken relay (K103) – NEC EA2-5NJ.
I took the device apart and probed the relay, comparing the result with other two relays.
It should have pins 2,3 and 8,9 shorted when off and 3,4 with 7,8 when on.
My relay has all the pins 2,3,4,7,8,9 shorted together – that is definitely not desired.
I ordered a new relay from Mouser and when it arrives I will replace it and see if that solves the problem.