DEC 3000/600 Alphaserver problems
Peter Coghlan
cctalk at beyondthepale.ie
Wed Jan 12 18:09:00 CST 2022
On Wed, 12 Jan 2022 at 17:28:33 -0600 Richard Schauer via cctalk wrote:
> 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!
>
This stuff dates from around 1994 I think. My 47uF component is about
6 or 7mm x 3 or 4mm. Maybe a problem with squeezing a lot of capacitance
in could be that it wants to pop out again!
>
> 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 probably need to peer closely at all of mine and figure out how many I
need. There are about 50 of these things in each of three machines :-(
>
>> 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.)
>
The hot tweezer sounds very nice but I think I'll stick with what I have
for now. These machines have other problems and won't ever do anything
useful unless I get the cache issues sorted out so I don't necessarily
want to invest in new tools for them to end up not getting them repaired.
Many thanks.
Regards,
Peter.
>
> Richard Schauer
> KF9VP
>
More information about the cctech
mailing list