Yes, another repair thread about benchtop precision DMM. This time it's not so precise, as usual stuff I mangle with, but more typical and commonly used Fluke 8846 6.5-digiter.
This is possible, thanks to John for his donation in the name of science (and making another article).
I almost feel like it's Fluke invasion in the lab recently. It went from zero Fluke DMMs (87V is not accounted for) to three in no time.
Rear side already show some damage to us, by broken tab of the power entry block. No biggie, just 26$ part.
However when I try to power on thing, it just locks up in booting logo and nothing happens.
Let's see who's inside? Good old LM399H, Fluke resistor networks, ALTERA Cyclone 1 FPGA's and bunch of other goodness.
Transformer is rusty special, that's for sure. Nothing obviously broken. According to date codes on chips, it's made early 2006.
So I mangled with it for few hours, replaced all electrolytic caps (usual rule when doing any older than 10yr equipment repairs), applied freeze spray on Cyclone FPGAs and stuff around in testing for cold joints, and poof, thing suddenly came to life..
Too easy repair, I thought! I turned it off, on, off, on, seem to be working fine.
Okay, let's have it meet the Hulk (that's nickname for my zombie calibrator).
Connected, turned on for 10 minute warmup, hooked cable, and...
-3.8ppm on 10V, -3ppm on 1V, no worries.
-6.6ppm on 100V, spot on at 1000V, woohoo.
Resistance checks, +10.4 ppm on 10kohm 4W, -47 ppm on 10 ohm. Not too shabby.
ACV and DCI also working okay.
Almost spot on, lol, with zero warming up time. Too good to be true, right?
LAN port however does not work, cannot connect to it either in static IP mode, or DHCP. DHCP does not get any IP address from network. Perhaps LAN Phy is killed?
Whatever, connected GPIB, that worked. So I setup simple python script to datalog 10VDC and went to bed (it was 5:30 am already).
And sure enough, 10 minutes after I closed my eyes, poor meter died.
It hangs on same power on initializing screen.
BTW, Firmware on it is really old 1.0x, does anybody have newer 2.xx firmwares for 8846A? Fluke removed it from website for no good reason
Any ideas what to pursue next?