DEC 3000/600 Alphaserver problems

[Richard Schauer]

On Wed, 12 Jan 2022, Peter Coghlan via cctalk wrote:
> They do have spikes of solder sticking out from the positive ends

Yes, those are tantalum caps.  The "hat" as I've always called it marks 
the positive end, and it should be part of the case, so it won't melt away 
in solder.  These things are a bit obsolete and aren't particularly 
common, but not impossible either.  I use a 100uF 0805-size (2mm x 1.25mm) 
one of these on a weird board we build for a customer at work; getting 
that much capacitance in a part that small always amazes me!

I hit Ebay to see if I could find something vaguely like what you have. 
The first listings that looked plausible were 194453105893 and 
203613355685.  I'm not saying they're the right size, or voltage, or 
anything like it, but it'll get you a manufacturer's part number that you 
can search for and find like ones.  His price seems high too.  You could, 
of course, sub an ordinary tantalum.

> I managed to desolder one of them from the middle of the picture using
> two soldering irons.  I am not very good at this surface mount stuff :-(
> It came out ok though.  I must have got lucky and picked a good one
> because it measured 47uF on the capacitance range on my multimeter.

Two irons is a perfectly valid method of removing SMT parts, if you're 
quick!  Ever heard of a hot tweezer?  It's two little irons, hinged at the 
top.  I have a variety of tips for mine and prefer it to hot air for most 
small things.  (Well, for routine work I usually have a chisel tip on my 
iron, and can get across both ends of something up to 0805-size and sweep 
it off the board.  1206 and bigger, you have to get creative, or use the 
hot tweezer.)

Richard Schauer
KF9VP