[Elecraft] Some reassurance needed please.

Mon Jun 16 17:34:01 2003

Hi Edward,

IC's and IC sockets are very insensitive to heat.  Two or three seconds to flow a good solder fillet will be aok. Even though you
don't need much solder to make an electrical connection, if you don't have a fillet, the joint is hard to inspect visually.  A good
looking fillet usually indicates a good joint, especially on leads that are already tinned, like IC's.

A very insidious problem is to forget to solder a lead of an IC.  It may make contact at first so the radio works but eventually it
may become intermittent; that can be very hard to find.  If only one lead doesn't have a fillet, it will be much easier to spot the
trouble with a careful visual inspection.

The actual measured resistance of some high resistance points can vary a whole lot depending on how your ohmmeter works and on the
orientation of the meter probes.  If the chart says >100K, for example, then almost any large reading will be ok. That doesn't
guarantee you don't have an open circuit, but it's a good start.  Open circuits can be very troublesome to find, but SHORT circuits
to a supply voltage or to ground are more likely to do damage before you can even start troubleshooting, so you want to minimize the
chance of that kind of problem.

73/ Bob - AG5Q

----- Original Message -----
From: "Kenworthy, Edward (EDS)" <[email protected]>
To: <[email protected]>
Sent: Monday, June 16, 2003 5:05 AM
Subject: [Elecraft] Some reassurance needed please.

> Hi all
>
> When soldering the ICs and IC sockets I took to heart the instruction to use
> the minimum solder - so I used just enough to fill the hole. The result is
> the solder joint doesn't look as nice and shiney as the others (because most
> of the solder is hidden and there's proportionatly more flux residue
> visible). Is this OK ?
>
> Secondly, checking the resistance, I note all the resistances are OK, so
> where it gives a range my readings are within the given range, but with some
> of the others that say >100K (eg the two oscillator pins on the PIC, pins 13
> and 14 I think) my reading is off the scale. Even with my DMM set to 2M
> range the resistance is off the scale. Yes I know "off the scale" is >100K,
> but why say >100K, why not >2M or >20M (if you see what I'm getting at) ?

> Edward