s0: ~/._backupDec 14, 2020
Fedi electronics peeps! Does anyone recognise this component? It’s marked R4 and looks like a 3 watt resistor but is confusingly marked brown-white-white-black which doesn’t seem to be a valid resistor code, or if it was, far higher than common sense suggests given it has dissipated enough heat to brown the PCB. It measures 12.9kΩ in circuit.
Any ideas? 
Show threads0: ~/._backupDec 14, 2020
Ok so turns out that resistor seems to only power the “on” LED at the front so I don’t care much about it anymore. Hopefully I can find the real culprit
Show threads0: ~/._backupDec 14, 2020
Spent the last few hours reverse engineering the schematic and checking it. Any suggestions for possible culprits? The relay isn’t switching on. Sorry I forgot the silicon rectifier part number. R3 and R4 are 1-2W, others are 1/4W. Ignore scribbles on the bridge rectifier I drew diodes wrong at first.
Show threads0: ~/._backupDec 14, 2020
D3 was a zener I think? One of them.
Show threads0: ~/._backupDec 14, 2020
No wait D1 was the zener it’s visible in the picture oops
Show threads0: ~/._backupDec 14, 2020
I’ve never used silicon rectifiers before so I’m a bit stumped
Show threads0: ~/._backup
New day on the Furman line filter repair and I’ve brought a little XL6009 adjustable boost module to see if I can get high enough current for the relay contacts to close. Definitely wishing I had access to a TH desoldering gun and bench power supply at work.
Dec 14, 2020 at 10:35pmWeb
Show threads0: ~/._backupDec 14, 2020
Ok, the relay definitely works fine! Now to test all the diodes I suppose.
Show threads0: ~/._backupDec 15, 2020
THE CULPRIT IS CAUGHT! This poly cap which is in series with the bridge rectifier input is reading at only 55% of nominal! So the rectified voltage is too low to actually trigger the relay coil! Can’t believe I didn’t test this much earlier 
Show threadKirby Dec 15, 2020
@s0 Not sure who Carl is, but at least it realized it… "mef"ed 🤔