12 Jun
2016
12 Jun
'16
1:38 p.m.
Hi folks,
Got a couple of Apple ][s that were rescued from a steelworks outbuilding
and as usual they have ASTEC power supplies with .1uF and .01uf RIFA
look-at-me-and-I'll-explode caps in and I'm running out of spares.
What's the current considered replacement for these? There seems to be a
wide range available with even wider ranging prices from EVOX, VISHAY,
MATSUSHITA, PANASONIC (ok, matsushita again), Iskra, KEMET etc.
Drowning in options, not just heavy rain :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
12 Jun
12 Jun
2:45 p.m.
On Jun 12, 2016, at 1:38 PM, Adrian Graham <witchy
at binarydinosaurs.co.uk> wrote:
Hi folks,
Got a couple of Apple ][s that were rescued from a steelworks outbuilding
and as usual they have ASTEC power supplies with .1uF and .01uf RIFA
look-at-me-and-I'll-explode caps in and I'm running out of spares.
What's the current considered replacement for these? There seems to be a
wide range available with even wider ranging prices from EVOX, VISHAY,
MATSUSHITA, PANASONIC (ok, matsushita again), Iskra, KEMET etc.
Explode? Those are ceramics caps, right? Are these the line inlet filter caps, or later
on? For line inlet, you need line rated caps, which have quite high voltage ratings for
good margin. Apart from that, I would think they should all work. I've used
Panasonic caps before, but Matsushita, Vishay and Kemet are also names I know and would
use. I don't know Evox or Iskra.
paul
2:49 p.m.
Explode? Those are ceramics caps, right? Are these
the line inlet
The ones I have seen are metalised paper and do have a deserved
reputation for being antisocial. They split open and emit clouds of
evil-smelling magic smoke.
filter caps, or later on? For line inlet, you need
line rated caps, which
have quite high voltage ratings for good margin. Apart from that, I
IIRC, the 'X2' marking means they are designed to be connected across the
mains (from live to neutral). A 'Y' or 'Y2' (which is designed so it
cannot fail
short-circuit) is used between one side of the mains and safety earth (ground).
The latter generally have a smaller capacitance than the former.
I suspect any known brand would be OK. I must admit I never buy components
on E-bay, I go to somewhere like RS components or Farnell. They may be more
expensive, but it is less of a gamble.
-tony
3:29 p.m.
On 12/06/2016 19:49, "tony duell" <ard at p850ug1.demon.co.uk> wrote:
Yep. Famous here in the UK for being used in every single Acorn BBC Micro
PSU (also ASTEC) plus a lot of monitors and TVs of that era. Classrooms all
over the land with that oh-so-familiar smell. Also my kitchen on Monday
night.
According to my reading whilst not cleaning filthy Apple ][s that's correct.
Explode? Those are ceramics caps, right? Are
these the line inlet
The ones I have seen are metalised paper and do have a deserved
reputation for being antisocial. They split open and emit clouds of
evil-smelling magic smoke. filter caps,
or later on? For line inlet, you need line rated caps, which
have quite high voltage ratings for good margin. Apart from that, I
IIRC, the 'X2' marking means they are designed to be connected across the
mains (from live to neutral). A 'Y' or 'Y2' (which is designed so it
cannot
fail short-circuit) is used between one side of the mains and safety earth
(ground). I suspect any known brand would be OK. I must admit I
never buy components
on E-bay, I go to somewhere like RS components or Farnell. They may be more
expensive, but it is less of a gamble.
Exact modern replacements are roughly ukp2 each from Farnell which is half
the price of some ebay chancers, some other reading I was doing suggested
EVOX/KEMET or WIMA so that'll do me.
Cheers!
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
3:31 p.m.
The ones I have seen are metalised paper and do have a deserved
reputation for being antisocial. They split open and emit clouds of
evil-smelling magic smoke.
Yep. Famous here in the UK for being used in every single Acorn BBC Micro
PSU (also ASTEC) plus a lot of monitors and TVs of that era. Classrooms all
over the land with that oh-so-familiar smell. Also my kitchen on Monday
night. Exact modern replacements are roughly ukp2 each from
Farnell which is half
the price of some ebay chancers, some other reading I was doing suggested
EVOX/KEMET or WIMA so that'll do me.
I think I would go for those.
Actually, while we all moan about the original RIFA ones, they have lasted
over 30 years in most cases. I don't think that's too bad. If the replacements
last as long then I won't complain.
-tony
3:40 p.m.
Those Rifa paper-dielectric caps are very common in the Astec power supplies that I have
found in most of my TRS-80 gear. After having one cook off on me in my Model 12, I replace
them all on sight with Panasonic safety-rated poly film caps. My hypothesis is that
moisture gets into the paper dielectric through the visible cracks that I have seen in the
outer case of every single 80s-era Rifa cap I've looked at. Since poly film caps are
supposed to be much less prone to absorbing moisture than paper dielectric caps, even when
their outer seal fails, I expect the poly film caps to last much longer.
I can look up the part numbers from Digi-Key that I used if necessary. I think that any
safety-rated poly film caps with suitable lead spacings, same or higher voltage ratings,
and similar capacitance should be fine.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
3:46 p.m.
On 12/06/2016 20:31, "tony duell" <ard at p850ug1.demon.co.uk> wrote:
They turn up everywhere. A couple of months back I was
upgrading a TRS-80
Model 4 for a friend. It had a couple of said capacitors which filled my
Large Machine Room with magic smoke... Also found them in HP machines.
Fortunately, they don't do much other damage when they go. They do
not catch fire in my experience. They may blow a fuse or trip the RCD in
the consumer unit if you are unlucky, but nothing worse.
Or make a co-worker absolutely lose his shit because a cooling fan blows the
smoke forcibly outwards :)
Actually, while we all moan about the original RIFA
ones, they have lasted
over 30 years in most cases. I don't think that's too bad. If the replacements
last as long then I won't complain.
True, and most of the time I know to check first to see if there are any
present and what state they're in - this Apple one is about to go. Monday's
was in the monitor of an ICL One-per-desk (aka a Sinclair QL with beefed up
innards and redesigned microdrives) and I just forgot to look.
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
2:57 p.m.
On 06/12/2016 10:38 AM, Adrian Graham wrote:
Got a couple of Apple ][s that were rescued from a
steelworks
outbuilding and as usual they have ASTEC power supplies with .1uF and
.01uf RIFA look-at-me-and-I'll-explode caps in and I'm running out of
spares.
What's the current considered replacement for these? There seems to
be a wide range available with even wider ranging prices from EVOX,
VISHAY, MATSUSHITA, PANASONIC (ok, matsushita again), Iskra, KEMET
etc.
Drowning in options, not just heavy rain :)
The vendor doesn't matter much, but I use polypropylene safety caps
mostly because they tend to be closer in size to the nasty Rifas. Just
make sure that the device has the proper safety rating. PP caps are
quite stable.
--Chuck
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