Dying VaxStation 4000 VLC - help?

From: Mark Tapley <mtapley_at_swri.edu>
Date: Mon Nov 25 08:33:01 2002

>Excellent. If you can use the right tools, do so. But it is _possible_ to
>do SMD rework using a normal (good) soldering iron.

I'll ask. But now I'm convinced the board has some hope of living, I
hesitate to address it myself...

>Are there any marking at all. You mentioned an orange band(s). How many?

One. I shouldn't have said "band", it's really the whole outside of the
component except the contacts at either end. It looks way too wide to be a
color-code band.

>Wait a second. The meter is 20kOhm/V right. I have no idea what range
>you're using, but lets say it's a 10V range. So the meter's resistance is
>200k.

Yep, 0-15V range.

>Now, it's a consequence of Thevenin's (?spel) theorem that the output
>impedance of a potential divider is the given by the 2 resistors in
>parallel. Here you'vr got 11500 Ohms and 61900 ohms. The equivalent
>resistance of those in paralle is 9.7k. So the meter is 20 times as high
>an impedance. That would give approximately a 5% error. Not that bad.

Well, true if I'm right about the resistor values being 11.5k/61.9k. If
they are 10 times higher, then I'm sunk.

>I wouldn't. For one thing, desoldering SMD parts risks damaging the PCB
>and even more so the component (most manufacturers recomend against
>reusing desoldered SMD parts). After desoldering the value might not he
>right anyway. For another, you don't know that all the capacitors on that
>board should be the same value.

True even with the proper (hot-air) desoldering tools? But suits my
inclination anyway, except that I *would* like to know what that cap. is
supposed to be.
                                        - Mark
Received on Mon Nov 25 2002 - 08:33:01 GMT