10 Jun
2009
10 Jun
'09
1:57 p.m.
Ethan Dicks wrote:
some of the older boards that used transistors for logic. one place
you would see those is
in an 8l or straight 8 and part of the core memory subsystem of the
omnibus machines.
Its rare to see the top epoxy pop off but it happens. usually the part
either fails
or is most often thermally intermittent.
Lot's of years working with transistors from that era and noo small
amount of DEC scrap
boards during my time with DEC for spares and as resource.
Allison
On Tue, Jun 9, 2009 at 5:38 PM, Allison<ajp166 at
bellatlantic.net> wrote:
They are essentially the same die but due to mounting and the absence of
the metal the
pn2222 does not stand he same Ic and power dissapation. if you really
need the plastic
part you might as well use the 2n3904.
Way too much information.. What he needs to know
is what can he buy now that
should work to replace a 2n3009?
I could use that info, too, since I also have older DEC equipment that
uses the 2N3009.
Answer: the 2N2222A (metal can not the plastic
PN2222) has the same or close
enough FT, Ic and breakdown voltages. It would be my first choice if I could
not purchase/salvage the exact part. Also the 2n2222A is available and usually
cheap. I buy them usually in for groups of 25 for about $0.08US each.
What is different about the metal can and the plastic case part? I
have a few of each, and have so-far interchanged them in circuits
where performance isn't an issue (i.e., where a 2N3904 would work
fine, too). Obviously 2N2222s aren't expensive, but I'd like to know
why I should set aside the metal-cased ones for repairing specific
items.
The only case
where they type transistor is a bit fussy is some of the faster
flip chip cards (logic) and SMPS.
What categories of FLIP-CHIPs are you thinking of when you say
"faster"? I have three R-series CPUs and a few DF-32s. I have yet to
delve into component-level repair, but I know I'll need to soon.
FYI: Older DEC
machines like straight-8 and friends used a lot fo the ceramic
epoxy parts similar to the 2n3638 and 2n3563.
Good to know (since I have more than one item from that era).
Those are ceramic headers with
a block of epoxy covering the die and are prone to popping the epoxy and the
symptom works when cold or mechanically intermittent.
Is that visually apparent, or is that an internal fault? If I
identified a bad transistor and removed it from a FLIP-CHIP, would it
be difficult to set up something with an oscilloscope to watch some
output then tap on the transistor to watch the trace "change" to
verify mechanical fragility?
Thanks,
-ethan