Repair Safety First

[Don Moose]

...ah, but, they're just two sides of the same equation (ha,ha)!

t.rise = 2.2*R*C = 2.2/(2*pi*ƒ.high) = 0.35/ƒ.high

...and, their ratio is a constant: 0.35 = t.rise/ƒ.high

...(wink,wink)!

Right, but with a 64mA driver on a 12" trace, a 100kHz signal is high speed because F.high is, like, the 9th harmonic. This is a problem for old designs that suddenly don't work when a classic 74HC part gets moved to a faster process geometry.

[Mark Black]

Lol just came across this thread. I know this has become a safety last thread, but in all seriousness, how would you handy techs go about properly securing yourself when working on a tube amp?

There is no such thing as absolute safety in this business (or probably in life for that matter). Even though I think I am pretty careful (timid even, maybe sometimes) I just got jolted this week by probably better than 300V RMS off the secondary of a power supply transformer due to a microscopic crack in a trace (happened to be the chassis/center-tap reference) on a PC board. Try to never complete a circuit...

Also, how did you more experienced techs get where you are in your work? Im currently a first year electonics student, and im interested in knowing how everyone else has learned their junk Yesterday 05:46 PM

I have always been curious to know how things work and how they break. Took electronics classes in high school and community college back when they were still teaching vacuum tube technology in the early semesters (boy I wish I had paid more attention but who knew...?). Still got my slide-rule around somewhere.

Took another year's worth of college classes about 15 years ago, where I learned that they don't teach much about the kind of stuff we deal with anymore - it's all about digital, SMD, and board-level troubleshooting with only a nod to tubes and discrete transistor circuits. Not much at all about linear/analog stuff.

I also made my "living" for a time in a band, and therefore was always too broke to pay someone else to fix my (and my band-mates') stuff when it went sideways...

[Enzo]

Safety is knowing what you are looking at.

My daddy bought me a little radio kit in 1953-1954 thereabouts. Been learning ever since. Self taught. Was into amateur radio as a kid but also got into audio design. Took high school electronics. College for physics major. Took up rock and roll and toured oh 1969-1973. Been riding the bench the last 33 years.