Re: Valve amp longevity

"Stan Barr" <stanb45@xxxxxxxxxxxxxx> wrote in message
news:slrne1u47g.4td.stanb45@xxxxxxxxxxxxxxxxxxxxxxxxxxx
On Mon, 20 Mar 2006 19:02:03 -0000, Alex Knight
<alexmknight@xxxxxxxxxxxxxxxxx>
wrote:
I think Netdog has a good point - a point-to-point hand wired amp will
last, and be worth maintaining, like a very good old car.

I've spent quite a bit of time over the past 40 years or so resoldering
bad
or failed joints in hand-wired electronics, from TVs to industrial control
gear. Give me a good reliable thick fibreglass pcb any time!
The sort of soldering you get from a poorly trained, bored and
uninterested
operative* on Friday afternoon with knocking-off time approaching leaves a
lot to be desired. Often the problems don't show up until years later...
Lead-free solder makes the problems worse.

* I've done a _lot_ of soldering in my time and I still do the odd
clunker!

FWIW, I agree - mostly. Point-to-point wiring vs PCB is an old, tired,
boring argument.

However, there is one small grain of truth there. With PCB
design/construction, there has sometimes been too much dependence on the
PCB/joints as a means of physical support, meaning:
- Heavy components need to be secured - not just by the soldered joints
- Connectors are stress points - connectors soldered to PCBs without
strain relief are *the* single most unreliable component
- Valve bases onto PCBs.... hmmm... depends.

One other point: back in the days when PTP was common, soldering was a very
carefully taught craft in industry. I remember DOI drawings of the various
kinds of joint (lay-on, wrap, etc) and their acceptable shapes. (Similarly,
a wireman was a skilled operator - some of the looms one saw [and still
occasionally does see] were works of art - wire sculptures, beautifully
done.) With PTP, one was expected to make a good mechanical joint *before*
soldering - i.e. it was strong.

It is entirely possible to make an unreliable PCB - but it's not down to any
inherent weakness in PCBs per se. It's down to a bit of common sense in the
design and production engineering depts.

Also - these kinds of failures are very easy to fix. A matter of minutes.
And, like Stan, I've seen just as many badly-soldered PTP assemblies as
poorly-conceived PCBs. (I routinely open up a new PTP amp - esp. if made in
China - to redo the soldering before trusting it.)

Steve
http://www.fivetrees.com


.

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