Safety tip of the day

[jshorva65]

My worst-yet experience with a filter cap was while I was repairing an old Harman-Kardon CA-100 PA / Paging amp (100W RMS, P-P 8417's running 645V B+ and 325V G2 from a full-wave doubler circuit) and preparing to add a custom-designed Guitar Preamp sub-chassis (minibox with two tubes, five pots, and appropriate connectors to draw power from a 5-pin socket H-K provided for a two-channel Mic Preamp for optional Mic 3 and Mic 4 and feed the Line Out signal into the RCA jack that H-K provided for the same Preamp accessory). The original problem was that the amp's output would intermittently go dead, which I traced to intermittent loss of G2 supply to the 8147's. Unplugged AC power, flipped the chassis, noticed a cold-solder joint where the G2 lead was supposed to connect to the junction of the two (about 100uF/450V) filter caps and power transformer secondary. I was about 12 years old at the time, and thought "looks like an easy fix" as I picked up the solder and soldering gun. Next thing I remember was picking myself up off the floor, fetching the spool of solder from the other side of the room, and gluing the broken case of my Weller D550 back together from where it had hit the floor and cracked like an egg. Definitely learned my lesson about remembering to discharge electrolytics!!!