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From: krw on 17 Jan 2010 19:33
On Sun, 17 Jan 2010 16:10:14 -0800 (PST), b
<reverend_rogers(a)yahoo.com> wrote:

>On 17 ene, 14:43, aemeijers <aemeij...(a)att.net> wrote:
>
>>
>> 20-30 years ago, maybe. Most consumer electronics from the last couple
>> of decades, the components are wave-soldered, purpose-built, and
>> unlabeled, other than on the circuit diagram in the manual you can't
>> get.
>
>'purpose built and unlabelled' components? what does that mean? In
>fact, I suspect it means nothing as it is gibberish, although I
>imagine most components are 'purpose built' for something - resistors
>for providing resistance for one. Hate to tell you, but that's been
>going on a lot longer than 2 decades!

Custom ASICs and components with their labels either removed or with
the box manufacturer's part numbers. If you've been around that long
and haven't seen these, you're blind.

>As for unlabelled, I'd love to know what kind of 'unlabelled' gear
>I've been missing these last two decades. Those of us who work on
>these items daily can identify the components by reading those cute
>little coloured stripes or printed text on them. If need be (for
>example if a component is destroyed) we even sometimes look for the
>component reference off the pcb, and consult the schematic. You know,
>you can even find lots and lots of them for free on sites like
>eserviceinfo.com. Try it one day.

I'd like you to point out these "colored stripes" on SMT devices
(almost everything is, anymore). Most SMT devices, particularly
capacitors aren't marked with value. If you can find a schematic
*maybe* it'll help.

From: whit3rd on 17 Jan 2010 20:58
On Jan 17, 4:10 pm, b <reverend_rog...(a)yahoo.com> wrote:
> On 17 ene, 14:43, aemeijers <aemeij...(a)att.net> wrote:
>
>
>
> > 20-30 years ago, maybe. Most consumer electronics from the last couple
> > of decades, the components are wave-soldered, purpose-built, and
> > unlabeled, other than on the circuit diagram in the manual you can't
> > get.
>
> 'purpose built and unlabelled' components? what does that mean?

It means 'jungle chip' components that were only produced for a few
months during one production run for a plant in Singapore, or power
packages with undocumented innards (maybe a Darlington and some
bias resistors, or maybe something else). Or it means little surface
mount chip components, with no printable surface for writing on.
Diode? Zener? Varactor? Fuse? Who can tell?

It also means programmed chips (PIC or PAL, gate arrays, or SOC
microprocessors). Anything you can swap for a known-good part
gives, at least in principle, a repair option. On a 'modern' consumer
item, there's lots of no-repair-option components. Even if you KNOW
it's a bad flyback, maybe the only thing you can do is order a full
deflection
board (about $400 for an old Apple iMac). When the gizmo turns
six years old, maybe you can't even get the $400 part.

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