Unusual Marshall amp fault

Heh... good catch!

I once had to debug a NAD stereo receiver I'd bought, used... bad crackling and popping on occasion, especially when tapped or banged. Like a lot of Japanese kit from a couple of decades ago, it had quite a few through-hold resistors in a "vertical" mounting position. Two had leaned, or been bend over just enough that their flying upper leads could make contact... POP!

I've seen those waste ends many times although can't recall having to find them as a result of a fault.

You're quite the detective, Nigel.

There were many boards where it was apparent that as part of the board processing, it had been placed in some sort of fixture that would pass along a belt sander-sort of arrangement to make all of the protruding leads a uniform length.

The scratches of the abrasive were visible, and burrs formed on all the leads were in the same direction.

I'd aways remove those waste tails/ends whenever I found them.. as some were long enough to reach other solder pads, and frequently were over, but not in good contact with adjacent pads.

-- Cheers, WB .............

Many of the old small transistor radios and similar portable gear from Japan often had lengths of clear tubing on all the long leads for that 'vertical' method of assembly. Standing those axial-lead components on end was the early method of making portable gear very compact.

I remember a radio which was only about 1-1/2" square and about 3/4" thick.. thin perforated aluminum speaker grille covering the front, and knobs on the side.. much more compact than any other radio at the time, 1963 maybe.

-- Cheers, WB .............

along

were

in

and

Not really detective work. My repair methodology starts (after initial powered up assessment if appropriate, then dismantling) with a full viewing under a x5 illuminated inspection lamp+ bulbous lens. Noting unusual device types, large R values if no schematic, state of solder joints, insulation, discoloured areas etc. I just saw what initially looked like a non-cropped off wiring-end ,through the valve base tag, ending too close to a pin 1 to pin 7, bare cross-coupling wire. Up to then I was thinking mains transformer interwinding fault.

Physical inspection is an important part of the diagnostic process. Good eye.

In my youth I impressed the hell out of one of my dad's friends, just because I spotted a break in a pcb trace in his broken transistor radio. ("Let spam take a look at it. He knows all about electronics.") A second with the soldering iron set it right.

I always do a shake test, even with new computers to check for fallen out screws, coins or other junk.