28 Aug
2019
28 Aug
'19
1:15 a.m.
I'm just curious how many people have powered up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and
4) when they were powered up. In both cases, the problem was with the
main line filter capacitor mounted on one of the power supplies. The
computers continued to work which was my first clue the problem was not
serious :).
Is this a normal problem with these older computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
28 Aug
28 Aug
1:32 a.m.
I have had this problem in various PSUs, particularly in MicroVAXen. In my case replacing
them has been fairly straightforward. Not had this with my TRS-80 (Model 1) though. I
think it is a fairly common problem.
Regards
Rob
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Marvin Johnston
via cctalk
Sent: 28 August 2019 09:16
To: ClassicCmp <cctalk at classiccmp.org>
Subject: TRS-80 Fireworks
I'm just curious how many people have powered up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and
4) when they were powered up. In both cases, the problem was with the
main line filter capacitor mounted on one of the power supplies. The
computers continued to work which was my first clue the problem was not
serious :).
Is this a normal problem with these older computers? I'm used to seeing the
electrolytics give problems, but this is the first time I've seen one of the X
type line filter caps blow.
1:34 a.m.
On 28/08/2019 09:15, Marvin Johnston via cctalk wrote:
I'm just curious how many people have powered up
their TRS-80
computers, and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3
and 4) when they were powered up. In both cases, the problem was with
the main line filter capacitor mounted on one of the power supplies.
The computers continued to work which was my first clue the problem
was not serious :).
Is this a normal problem with these older computers? I'm used to
seeing the electrolytics give problems, but this is the first time
I've seen one of the X type line filter caps blow.
This is very common for these paper line filters. I've had the same
failure with an Osborne 1, DECserver 200, DELNI and PDP-11/73. There are
many more devices that have them; generally anything with an Astec brand
power supply. I replace them before even powering up these days.
Matt
2:05 a.m.
Matt wrote:
On 28/08/2019 09:15, Marvin Johnston via cctalk
wrote:
I've had several instances of it with BBC Micros, also containing Astec brand
power supplies. Typically, when switched on after a long period of idleness,
the machine works fine for minutes to hours, then there is a quiet pop followed
by a whoosing noise and smoke starts pouring of the mains filter capacitor
while the machine continues to work away quite happily.
Regards
Peter Coghlan.
I'm just curious how many people have powered
up their TRS-80
computers, and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3
and 4) when they were powered up. In both cases, the problem was with
the main line filter capacitor mounted on one of the power supplies.
The computers continued to work which was my first clue the problem
was not serious :).
Is this a normal problem with these older computers? I'm used to
seeing the electrolytics give problems, but this is the first time
I've seen one of the X type line filter caps blow.
This is very common for these paper line filters. I've had the same
failure with an Osborne 1, DECserver 200, DELNI and PDP-11/73. There are
many more devices that have them; generally anything with an Astec brand
power supply. I replace them before even powering up these days.
30 Aug
30 Aug
1:07 p.m.
On Wed, 28 Aug 2019, Peter Coghlan via cctalk wrote:
I've had several instances of it with BBC Micros,
also containing Astec brand
power supplies. Typically, when switched on after a long period of idleness,
the machine works fine for minutes to hours, then there is a quiet pop followed
by a whoosing noise and smoke starts pouring of the mains filter capacitor
while the machine continues to work away quite happily.
Sometimes not even a pop:
https://unicorn.drogon.net/bbcSmoke.jpg
Biggest bang I've had was from an Apple //e PSU..
But yes - SOP: Change the X2's...
Gordon
28 Aug
28 Aug
2:07 a.m.
At 01:15 AM 28/08/2019 -0700, you wrote:
I'm just curious how many people have powered up
their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and
4) when they were powered up. In both cases, the problem was with the
main line filter capacitor mounted on one of the power supplies. The
computers continued to work which was my first clue the problem was not
serious :).
Is this a normal problem with these older computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
An extremely common problem with all old electronics from around that era.
The mains filter caps are commonly 'RIFA' brand metalized polyester film,
encapsulated in a clear-honey-coloured resin.
The problem is that the resin embrittles and shrinks with age, resulting in
many small cracks. (And sometimes large pieces falling off.)
The cracks let in moisture, which absorbs into the insulating film.
When that inevitably fails the resulting arc eats away at the thin metalization
film, vaporizing the adjacent plastic into foul-smelling greasy smoke. Often not
enough mains current gets drawn to trip the breaker, so the arcing ruin may go
on for some seconds - producing lots of smoke and stink. Also commonly destroying
the component value markings, so you have to guess about a replacement.
HP 62xx series bench power supplies have some RIFA caps and a circuit board inside
a closed metal box containing the mains pre-regulator TRIAC. When those RIFAs blow
the smoke condenses on everything inside the box. Cleaning that mess is really a pain.
RIFA caps may be the most hated components in electronics. Even worse than dipped
tantalums, popped electrolytics, and decaying urethane foam.
Replace on sight. Before trying a power up.
I was recently given a large pile of NIB (old) switchmode supplies of various sizes,
all the same manufacturer. About a third have RIFA mains filter caps. Grrr...
Guy
3:10 a.m.
On Wed, Aug 28, 2019 at 07:07:21PM +1000, Guy Dunphy via cctalk wrote:
[...]
RIFA caps may be the most hated components in
electronics. Even worse than dipped
tantalums, popped electrolytics, and decaying urethane foam.
Amiga collectors would say "batteries", since Commodore selected a brand of
rechargable cells which leaked board-eating acid. This also affected the Acorn
Archimedes, but only posh kids had those.
2:47 p.m.
Hello all,
S100 based computers have the same problem. I have had the caps in
the PS and on the individual boards go boom. Common failure mode for
electrolytics and tantalums.
GOD Bless,
rich!
On 8/28/2019 3:10 AM, Peter Corlett via cctalk wrote:
On Wed, Aug 28, 2019 at 07:07:21PM +1000, Guy Dunphy
via cctalk wrote:
[...]
RIFA caps may be the most hated components in
electronics. Even worse than dipped
tantalums, popped electrolytics, and decaying urethane foam.
Amiga collectors
would say "batteries", since Commodore selected a brand of
rechargable cells which leaked board-eating acid. This also affected the Acorn
Archimedes, but only posh kids had those.
3:46 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Guy Dunphy via
cctalk
Sent: 28 August 2019 10:07
To: Marvin Johnston <marvin at west.net>; General Discussion: On-Topic and
Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: TRS-80 Fireworks
At 01:15 AM 28/08/2019 -0700, you wrote:
In the UK it affects the BBC Model B models. Plenty of kits on E-Bay to fix.
Often cheaper than a single cap.
Dave
I'm just curious how many people have powered
up their TRS-80
computers, and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3
and
4) when they were powered up. In both cases, the problem was with the
main line filter capacitor mounted on one of the power supplies. The
computers continued to work which was my first clue the problem was not
serious :).
Is this a normal problem with these older computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
An extremely common problem with all old electronics from around that era.
The mains filter caps are commonly 'RIFA' brand metalized polyester film,
encapsulated in a clear-honey-coloured resin.
The problem is that the resin embrittles and shrinks with age, resulting
in many
small cracks. (And sometimes large pieces falling
off.) The cracks let in
moisture, which absorbs into the insulating film.
When that inevitably fails the resulting arc eats away at the thin
metalization
film, vaporizing the adjacent plastic into
foul-smelling greasy smoke.
Often not
enough mains current gets drawn to trip the breaker,
so the arcing ruin
may go
on for some seconds - producing lots of smoke and
stink. Also commonly
destroying the component value markings, so you have to guess about a
replacement.
HP 62xx series bench power supplies have some RIFA caps and a circuit
board
inside a closed metal box containing the mains
pre-regulator TRIAC. When
those RIFAs blow the smoke condenses on everything inside the box.
Cleaning
that mess is really a pain.
RIFA caps may be the most hated components in electronics. Even worse than
dipped tantalums, popped electrolytics, and decaying urethane foam.
Replace on sight. Before trying a power up.
I was recently given a large pile of NIB (old) switchmode supplies of
various
sizes, all the same manufacturer. About a third have
RIFA mains filter
caps.
Grrr...
Guy
30 Aug
30 Aug
10:27 p.m.
On Aug 28, 2019, at 2:07 AM, Guy Dunphy via cctalk
<cctalk at classiccmp.org> wrote:
An extremely common problem with all old electronics from around that era.
The mains filter caps are commonly 'RIFA' brand metalized polyester film,
encapsulated in a clear-honey-coloured resin.
The problem is that the resin embrittles and shrinks with age, resulting in
many small cracks. (And sometimes large pieces falling off.)
The cracks let in moisture, which absorbs into the insulating film.
I suspect those notorious Rifa brand capacitors would not be so problematic if they had
polyester film dielectric. But if I'm not mistaken, they don't; they have *paper*
dielectric!
Aside from that one correction, I agree with everything else you wrote about the likely
failure mechanism of these evil little rectangles of compressed smoke and fire.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
28 Aug
28 Aug
4:35 a.m.
On Aug 28, 2019, at 4:15 AM, Marvin Johnston via
cctalk <cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered up their TRS-80 computers, and ended up
with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and 4) when they
were powered up. In both cases, the problem was with the main line filter capacitor
mounted on one of the power supplies. The computers continued to work which was my first
clue the problem was not serious :).
Is this a normal problem with these older computers? I'm used to seeing the
electrolytics give problems, but this is the first time I've seen one of the X type
line filter caps blow.
This is well known issue on all Models of TRS-80, except the Model I. In fact, it is
almost guaranteed that your power supply main Rifa filter capacitor will blow within a few
minutes of when you first power up one of these TRS-80s after sitting for years if you
have the original caps. So much so that I was able to record one fail in spectacular
fashion.
https://youtu.be/njbwdbcfXjc <https://youtu.be/njbwdbcfXjc>
4:57 a.m.
On Wed, 28 Aug 2019 at 10:16, Marvin Johnston via cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
"They all do that, sir."
Computers older than 20y or so, that is. :-(
--
Liam Proven - Profile: https://about.me/liamproven
Email: lproven at cix.co.uk - Google Mail/Hangouts/Plus: lproven at gmail.com
Twitter/Facebook/Flickr: lproven - Skype/LinkedIn: liamproven
UK: +44 7939-087884 - ?R (+ WhatsApp/Telegram/Signal): +420 702 829 053
5:34 a.m.
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston via cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered up
their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
I've had identical experiences with Rifa caps as others here. One
thing about them, you don't need to be powered on. The caps are
usually on the hot side of the power switch. I've had a MicroPDP-11
and a Commodore D9060 sizzle when plugged in but powered off.
Is this a normal problem with these older computers?
I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
Rifa caps are notorious for reasons already described.
Found in a lot of 1980s gear, TRS-80, Commodore, DEC... Replace on sight.
-ethan
6:12 a.m.
On Wed, Aug 28, 2019, 8:35 AM Ethan Dicks via cctalk <cctalk at classiccmp.org wrote:
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston via
cctalk
<cctalk at classiccmp.org> wrote:
Trs 80 III / 4 absolutely yes these pop. I call it banana pancakes time
because that is what it kind of smells like.
At the vcf east we have an informal recocognition award titled "first to
smoke" that usually goes to the first exhibitor who loses a RIFA cap during
set up or on public display.
Bill
I'm just curious how many people have powered
up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
6:16 a.m.
It was at the Maker Faire, 1 year ago, we had these caps blow on 2 Apple II's. One ran
for less than an hour before going and the other ran for a day and the next day it also
blew ( it was my Apple II ). It now lives without the capacitor.
Dwight
________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Ethan Dicks via cctalk
<cctalk at classiccmp.org>
Sent: Wednesday, August 28, 2019 5:34 AM
To: Marvin Johnston <marvin at west.net>; General Discussion: On-Topic and Off-Topic
Posts <cctalk at classiccmp.org>
Subject: Re: TRS-80 Fireworks
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston via cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered up
their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
I've had identical experiences with Rifa caps as others here. One
thing about them, you don't need to be powered on. The caps are
usually on the hot side of the power switch. I've had a MicroPDP-11
and a Commodore D9060 sizzle when plugged in but powered off.
Is this a normal problem with these older computers?
I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
Rifa caps are notorious for reasons already described.
Found in a lot of 1980s gear, TRS-80, Commodore, DEC... Replace on sight.
-ethan
6:34 a.m.
Thanks everyone for the feedback... I had no idea. I'll be putting in an
order today with Digi-key (P/N 399-7483-ND) for probably around 25+ caps
or so since I have at least that many TRS-80 2s, 3s, 4s.
I guess my only question is are there other similar caps that also need
to be replaced? I'm well aware of the electrolytics and have that
project on the back burner right now (about 10 Model 100s to repair.) It
is nice that they are pretty trivial to replace!
Marvin
On 8/28/2019 5:34 AM, Ethan Dicks wrote:
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston via
cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered
up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
I've had identical experiences with Rifa caps as others here. One
thing about them, you don't need to be powered on. The caps are
usually on the hot side of the power switch. I've had a MicroPDP-11
and a Commodore D9060 sizzle when plugged in but powered off.
Is this a normal problem with these older
computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
Rifa caps are notorious for reasons already described.
Found in a lot of 1980s gear, TRS-80, Commodore, DEC... Replace on sight.
-ethan
6:50 a.m.
Be sure to read this article. The caps used in this capacity (pun intended) are
specialized...
https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-…
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Marvin Johnston via
cctalk <cctalk at classiccmp.org>
Sent: Wednesday, August 28, 2019 9:34 AM
To: Ethan Dicks; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: TRS-80 Fireworks
Thanks everyone for the feedback... I had no idea. I'll be putting in an
order today with Digi-key (P/N 399-7483-ND) for probably around 25+ caps
or so since I have at least that many TRS-80 2s, 3s, 4s.
I guess my only question is are there other similar caps that also need
to be replaced? I'm well aware of the electrolytics and have that
project on the back burner right now (about 10 Model 100s to repair.) It
is nice that they are pretty trivial to replace!
Marvin
On 8/28/2019 5:34 AM, Ethan Dicks wrote:
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston via
cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered
up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
I've had identical experiences with Rifa caps as others here. One
thing about them, you don't need to be powered on. The caps are
usually on the hot side of the power switch. I've had a MicroPDP-11
and a Commodore D9060 sizzle when plugged in but powered off.
Is this a normal problem with these older
computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
Rifa caps are notorious for reasons already described.
Found in a lot of 1980s gear, TRS-80, Commodore, DEC... Replace on sight.
-ethan
7:03 a.m.
The article I found online was:
http://www.akhara.com/trs-80/psrepair/index.html
But the reference you posted gave me some excellent perspective on the
what is what and why :)!
Marvin
On 8/28/2019 6:50 AM, W2HX wrote:
Be sure to read this article. The caps used in this
capacity (pun intended) are specialized...
https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-…
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Marvin Johnston via
cctalk <cctalk at classiccmp.org>
Sent: Wednesday, August 28, 2019 9:34 AM
To: Ethan Dicks; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: TRS-80 Fireworks
Thanks everyone for the feedback... I had no idea. I'll be putting in an
order today with Digi-key (P/N 399-7483-ND) for probably around 25+ caps
or so since I have at least that many TRS-80 2s, 3s, 4s.
I guess my only question is are there other similar caps that also need
to be replaced? I'm well aware of the electrolytics and have that
project on the back burner right now (about 10 Model 100s to repair.) It
is nice that they are pretty trivial to replace!
Marvin
On 8/28/2019 5:34 AM, Ethan Dicks wrote:
On Wed, Aug 28, 2019 at 4:16 AM Marvin Johnston
via cctalk
<cctalk at classiccmp.org> wrote:
I'm just curious how many people have powered
up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
I've had identical experiences with Rifa caps as others here. One
thing about them, you don't need to be powered on. The caps are
usually on the hot side of the power switch. I've had a MicroPDP-11
and a Commodore D9060 sizzle when plugged in but powered off.
Is this a normal problem with these older
computers? I'm used to seeing
the electrolytics give problems, but this is the first time I've seen
one of the X type line filter caps blow.
Rifa caps are notorious for reasons already described.
Found in a lot of 1980s gear, TRS-80, Commodore, DEC... Replace on sight.
-ethan
6:59 a.m.
On Aug 28, 2019, at 9:34 AM, Marvin Johnston via
cctalk <cctalk at classiccmp.org> wrote:
Thanks everyone for the feedback... I had no idea. I'll be putting in an order today
with Digi-key (P/N 399-7483-ND) for probably around 25+ caps or so since I have at least
that many TRS-80 2s, 3s, 4s.
I guess my only question is are there other similar caps that also need to be replaced?
I'm well aware of the electrolytics and have that project on the back burner right now
(about 10 Model 100s to repair.) It is nice that they are pretty trivial to replace!
Marvin
I?ve had very few problems with electrolytics in the many TRS-80s I?ve worked on. It
seems to be one of the places where Tandy did not cheap out. There are some tantalum
capacitors to be found in TRS-80s. These have a tendency to fail to short so I am wary of
them but still, I would probably not replace any unless they failed.
7:10 a.m.
Almost all of my Model 100s (around 8 or so) need to have all of the
electrolytics replaced. For some reason, they started leaking and
causing a problem with desoldering the bad parts. Upon close
examination, the leaking caps can be detected relatively easily. Some
information I saw somewhere indicated that the Chinese caps are the
worst offenders... they stole the formula but apparently "modified" it
slightly ending up with future problems.
Some of this information falls into the "I don't know what I don't know"
catagory. Nice having the tremendous volume of knowledge here to help out!
Marvin
On 8/28/2019 6:59 AM, Peter Cetinski wrote:
On Aug 28, 2019, at 9:34 AM, Marvin Johnston via
cctalk <cctalk at classiccmp.org> wrote:
Thanks everyone for the feedback... I had no idea. I'll be putting in an order today
with Digi-key (P/N 399-7483-ND) for probably around 25+ caps or so since I have at least
that many TRS-80 2s, 3s, 4s.
I guess my only question is are there other similar caps that also need to be replaced?
I'm well aware of the electrolytics and have that project on the back burner right now
(about 10 Model 100s to repair.) It is nice that they are pretty trivial to replace!
Marvin
I?ve had very few problems with electrolytics in the many TRS-80s I?ve worked on. It
seems to be one of the places where Tandy did not cheap out. There are some tantalum
capacitors to be found in TRS-80s. These have a tendency to fail to short so I am wary of
them but still, I would probably not replace any unless they failed.
7:51 a.m.
On Aug 28, 2019, at 10:10 AM, Marvin Johnston via
cctalk <cctalk at classiccmp.org> wrote:
Almost all of my Model 100s (around 8 or so) need to have all of the electrolytics
replaced. For some reason, they started leaking and causing a problem with desoldering the
bad parts. Upon close examination, the leaking caps can be detected relatively easily.
Some information I saw somewhere indicated that the Chinese caps are the worst
offenders... they stole the formula but apparently "modified" it slightly ending
up with future problems.
Some of this information falls into the "I don't know what I don't
know" catagory. Nice having the tremendous volume of knowledge here to help out!
Marvin
The 100 was a rebranded Kyocera so maybe they used inferior components compared to the
Made in Fort Worth machines. :)
9:30 a.m.
indicated that the Chinese caps are the worst
offenders... they stole the
formula but apparently "modified" it slightly ending up with future problems.
That was a while ago, and post-TRS-80 era.
Some of this information falls into the "I
don't know what I don't know"
catagory. Nice having the tremendous volume of knowledge here to help out!
Digikey, mouser, avnet, newark, etc.... and buy Pansonic or Nichicon 105
degree caps. Should be good for a good while.
- Ethan
9:06 a.m.
We were at this HOPE conference in NYC. We were helping with it in those
days, so we had some equipment at the ops area. A whole bunch of commotion
went down in the OPS area, including someone grabbing a fire extingisher
and jumping.
Watching this from a-far, we chuckled and I said, "Good thing this doesn't
involve us."
A few seconds later someone tells me that my TRS-80 model 4 started to let
out a bunch of magic smoke.
I mention it to one of the VCF'ers that was there. I'm pretty sure it was
Glitch. He is like, "Oh that's the rice paper capacitor at postiion C103
or something. A noise filter."
"Do you work on these often?" I reply. I figured this was the ninja of
TRS-80s or something. "No, pretty much never" he says.
Now I'm twice as confused. But whatever. We open the thing up and it is
the exact capacitor he mentioned. We just rmeoved it. And I'm still
confused as how he knew the exact capacitor that went off the top of his
head.
--
: Ethan O'Toole
9:23 a.m.
On Wed, Aug 28, 2019 at 5:06 PM Ethan O'Toole via cctalk
<cctalk at classiccmp.org> wrote:
We were at this HOPE conference in NYC. We were helping with it in those
days, so we had some equipment at the ops area. A whole bunch of commotion
went down in the OPS area, including someone grabbing a fire extingisher
and jumping.
Watching this from a-far, we chuckled and I said, "Good thing this doesn't
involve us."
A few seconds later someone tells me that my TRS-80 model 4 started to let
out a bunch of magic smoke.
I mention it to one of the VCF'ers that was there. I'm pretty sure it was
Glitch. He is like, "Oh that's the rice paper capacitor at postiion C103
or something. A noise filter."
"Do you work on these often?" I reply. I figured this was the ninja of
TRS-80s or something. "No, pretty much never" he says.
Now I'm twice as confused. But whatever. We open the thing up and it is
the exact capacitor he mentioned. We just rmeoved it. And I'm still
confused as how he knew the exact capacitor that went off the top of his
head.
FWIW my Model 3 and Model 4 have done just that. As did my Acorn
Cambridge when I was setting it up for a demonstration about a month
ago. It's a common failure in all sorts of equipment, from all manufacurers.
Don't think that Radio Shack are using inferior components here, I've had
HP and Tektronix units do the same thing.
Although I don't replace components for fun, I normally replace all the
capacitors in the mains filter (class X across the mains, class Y from
either side of the mains to earth ground). The class Y ones don't normally
fail in this way, but....
As for knowing which capacitor it was even without familiarity with the
unit. The smell and smoke are quite distinctive. And the macbine normally
keeps on running, indicating a mains filter problem most of the time.
Now for the secret... The mains filter is the first stage of the power supply.
So it has the lowest numbered capacitors. There's normally a filter choke
unit with a capacitor across the mains on each side. And a pair of capacitors
on one side of that from each mains line to ground. So they are likely to be
C1...C4 or C101...C104 or something like that.
So guess 'C103 or thereabouts' and you won't be far off :-)
-tony
3:50 p.m.
Quite normal - the capacitors dry out after about 30 or 40 years - there's lots of
info around on replacing them with a polymer capacitor. I have over 20 TRS-80's with a
large contingent of Model 3, 4, 4Ps, 12 and 16s - all had the same issue so if I acquire
one now I do a pre-emptive strike before powering up.
Kevin Parker
0418 815 527
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Marvin Johnston via
cctalk
Sent: Wednesday, 28 August 2019 6:16 PM
To: ClassicCmp <cctalk at classiccmp.org>
Subject: TRS-80 Fireworks
I'm just curious how many people have powered up their TRS-80 computers, and ended up
with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and
4) when they were powered up. In both cases, the problem was with the main line filter
capacitor mounted on one of the power supplies. The computers continued to work which was
my first clue the problem was not serious :).
Is this a normal problem with these older computers? I'm used to seeing the
electrolytics give problems, but this is the first time I've seen one of the X type
line filter caps blow.
9:54 p.m.
On 8/28/2019 4:50 PM, Kevin Parker via cctalk wrote:
Quite normal - the capacitors dry out after about 30
or 40 years - there's lots of info around on replacing them with a polymer capacitor.
I have over 20 TRS-80's with a large contingent of Model 3, 4, 4Ps, 12 and 16s - all
had the same issue so if I acquire one now I do a pre-emptive strike before powering up.
I suspect, cost cutting is also a factor with consumer vs industial
products for part replacement. Ben.
29 Aug
29 Aug
2:25 a.m.
Kevin,
As I am sure others will say, I believe that the problem with the "X" filter
caps is that the case becomes cracked and you get moisture ingress....
Dave
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Kevin Parker via
cctalk
Sent: 28 August 2019 23:51
To: 'Marvin Johnston' <marvin at west.net>; 'General Discussion:
On-Topic and
Off-Topic Posts' <cctalk at classiccmp.org>
Subject: RE: TRS-80 Fireworks
Quite normal - the capacitors dry out after about 30 or 40 years - there's lots
of info around on replacing them with a polymer capacitor. I have over 20 TRS-
80's with a large contingent of Model 3, 4, 4Ps, 12 and 16s - all had the same
issue so if I acquire one now I do a pre-emptive strike before powering up.
Kevin Parker
0418 815 527
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Marvin Johnston
via cctalk
Sent: Wednesday, 28 August 2019 6:16 PM
To: ClassicCmp <cctalk at classiccmp.org>
Subject: TRS-80 Fireworks
I'm just curious how many people have powered up their TRS-80 computers,
and ended up with a bang and a room filled with smoke?
So far, I've gotten the fireworks in two out of two TRS-80s (model 3 and
4) when they were powered up. In both cases, the problem was with the main
line filter capacitor mounted on one of the power supplies. The computers
continued to work which was my first clue the problem was not serious :).
Is this a normal problem with these older computers? I'm used to seeing the
electrolytics give problems, but this is the first time I've seen one of the X type
line filter caps blow.
1939
days inactive
1942
days old
26 comments
20 participants
participants (20)
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abuse＠cabal.org.uk -
ard.p850ug1＠gmail.com -
bfranchuk＠jetnet.ab.ca -
billdegnan＠gmail.com -
cctalk＠beyondthepale.ie -
dave.g4ugm＠gmail.com -
dkelvey＠hotmail.com -
ethan.dicks＠gmail.com -
ethan＠757.org -
gordon+cctalk＠drogon.net -
guykd＠optusnet.com.au -
lproven＠gmail.com -
marvin＠west.net -
matt＠9track.net -
mechanic_2＠charter.net -
nf6x＠nf6x.net -
pete＠pski.net -
robert.jarratt＠ntlworld.com -
trash80＠internode.on.net -
w2hx＠w2hx.com