I have recently become the proud owner of a 475 that I found abandoned at the side of a road! Other than a couple dents in the casing, it appears to be in pretty good condition.
After replacing the fuses, I was greeted with what appeared to be a very fuzzy trace when turning the power on. However, very soon afterwards, a resistor directly adjacent to the J4 connector on board A9 (listed in the manual as 'interface circuit board assembly') began to smoke, at which point I powered it off. One of the leads of the resistor in question is connected to the positive side of a orange dipped (tantalum?) capacitor, which leads me to suspect that it may be the culprit, given all that I have read so far regarding worn out and failed capacitors on 400 series scopes. When testing the capacitor in the board, it certainly seems like it's shorted, which I presume would explain the smoke from the adjacent resistor.
I'm hesitant to power it on again to check all the rail voltages in case I further damage the resistor. I suppose I should start by verifying which capacitors are good and bad, and replacing the failed ones? In this case, is there a definitive criteria for determining which capacitors are good and which need to be replaced? Or should my attention be directed elsewhere first?
Any advice and suggestions would be greatly appreciated.
