On Thursday, December 3, 2015 at 12:34:56 PM UTC, Mark Zacharias wrote:
OK, so it appears there is very little to discuss on this group in areas
like repairing audio components, amps, receivers, power supplies, etc these
days.

I "tune in" here almost daily and rarely find anything of interest to me.

Maybe we could share some "war stories" of cool repairs we have done in the
past.

Re-live some past glories?

The first time you traced down a bad reset line for a microprocessor?

That integrated amp that blew a channel about once a year until you caught
that bias diode occasionally opening up?

Sansui 5000A's? (yuck)

Crappy Euro caps in Tandberg tape decks?

Those times you sweated whether you could even get this thing put back
together?

Any more recent successs stories to brag about?

C'mon, don't we all enjoy patting ourselves on the back, really?


Mark Z.



My favourite - I was working for a Pro PA hire compoany in London. They had supplied a monitor system for a BBC recording of Public Image Ltd at Maida Vale Studios, London. The system was buzzing like crazy and none of the Sound Company or BBC engineers could work out why. They were about to pull the whole gig.
They sent me down as a last faint hope.

It was obviously some kind of mains problem, but everything seemed to check out fine on multimeters. Earths, Neutrals were all at 0v.
Eventually I decided to plug in my scope, to discover that instead of a nice straight line accross the display, it was massively modulated.
Clearly the scope's Earth wasn't a proper Earth but had some mains on it.
I then was able to track down the fault - one multi-way extension cable attatched to the many, many pieces of equipment had Earth and Neutral reversed, thus connecting all Earths and Neutrals in the middle of the studio as well as back at the mains Intake.

Ripped the offending extension out, the buzzing ceased immediately, and the BBC and Public Image Limited got their recording and the Sound Company didn't lose the gig or it's reputation.



Gareth.