Risc PC PSU questions

[Samuel Kock]

Hi there

I ave a couple of question wrt to a RISC PC PSU (70W) I have here:

It does not want to work! I have replaced the fuse, but when I connect it to
a RPC mobo and HDD, the fan spins for about a quarter of a revolution and
stop. And nothing else happens. Is there anything else I can do, or is this
a problem for the big boys? Anybody else done fault diagnosis on RPC PSU's?

Secondly, where can I find a power siwtch for the RPC. That is the little
white square on/off button? The compuer seems to have lost its one.

If I can get these two things fixed I will have (yet another!) working RISC
PC... :)

Thanks all!

Samuel
--
Samuel Kock
Pretoria, South Africa
Bio: http://go.to/skock/bio.htm
Put people on hold when possible.

[Henry Falkner]

"skok" <samuelk@depsammed.com> wrote in message
news:bfok75$qvm$1@ctb-nnrp2.saix.net... Hi there I ave a couple of question wrt to a RISC PC PSU (70W) I have here: It does not want to work! I have replaced the fuse, but when I connect it
to a RPC mobo and HDD, the fan spins for about a quarter of a revolution and stop. And nothing else happens. Is there anything else I can do, or is
this a problem for the big boys? Anybody else done fault diagnosis on RPC
PSU's?

Early Risc PC PSUs were underrated, and blew components, even with no
podules in them. The first blown PSU I did not even bother to get repaired,
since an uprated version was affordable. That one also blew after a couple
of months. I bought a third one, but got the second one repaired, which is
still working.

These are switch mode power supplies - the mains is converted to a high
frequency, which needs only a small transformer for voltage conversion. The
high frequency is generated by an 'oscillator' with the peculiarity that the
spaces between the waves vary. This variation is the result of a 'feedback'
circuit that changes the 'mark space ratio' depending on how much current
the computer is using. Also, the top and the bottom of the waves are clipped
to make them 'square waves'. These are then 'rectified', because the
computer works with direct current at several voltages.

To get the 'square waves', the oscillator is driven into 'saturation', i.e.
the transistor(s) in them is turned 'hard on' for short times. If a fault in
the computer, or the PSU itself, turns on the transistor(s) on all the time,
the PSU starts self-destructing, with a severity depending on its design and
the 'overload'. Switch-mode power supplies are supposed to have shut down
device built into them to prevent 'catastrophic failure', but the Acorn ones
seem to prefer self-destructing to shutting down before damage has occurred.

All this means, repairing these supplies involves a learning curve, until
you know what usually blows. Not catching all the blown components first
time may mean, that the supposedly repaired PSU blows again.

Henry

[Steve Fryatt]

On 24 Jul, skok wrote in message
<bfok75$qvm$1@ctb-nnrp2.saix.net>:
I ave a couple of question wrt to a RISC PC PSU (70W) I have here: It does not want to work! I have replaced the fuse, but when I connect it to a RPC mobo and HDD, the fan spins for about a quarter of a revolution and stop. And nothing else happens. Is there anything else I can do, or is this a problem for the big boys? Anybody else done fault diagnosis on RPC PSU's?

Try Googling this group for "RiscPC PSU diode" or something along those
lines. There's a common failure mode due to an underrated output schottky
diode, which should be fairly easy to diagnose and fix. If it isn't that,
it could be more tricky to find.

*However* (usual disclaimer), if you're not sure about power electronics,
you may want to simply buy a replacement or get it fixed professionally.
There are voltages up to 400Vdc inside the box, which may hold up longer
than normal as the PSU isn't working properly. Give it at least several
hours to discharge after unplugging it from the mains before removing the
cover and take care.

--
Steve Fryatt - Leeds, England http://www.stevefryatt.org.uk/

* Jul 24 1817 - Novelist Jane Austin died and was buried in Winchester
Cathedral.

[Greg]

In article <bfok75$qvm$1@ctb-nnrp2.saix.net>, samuelk@depsammed.com
says... Hi there I ave a couple of question wrt to a RISC PC PSU (70W) I have here: It does not want to work! I have replaced the fuse, but when I connect it to a RPC mobo and HDD, the fan spins for about a quarter of a revolution and stop. And nothing else happens. Is there anything else I can do, or is this a problem for the big boys? Anybody else done fault diagnosis on RPC PSU's?

Look at -
http://groups.google.co.uk/groups?q=Patrick+Herborn+PSU+group:comp.sys.ac
orn.*+group:comp.sys.acorn.*&start=10&hl=en&lr=&ie=UTF-
8&group=comp.sys.acorn.*&selm=482cc7183asabell%40no-spam.co.uk&rnum=12
Secondly, where can I find a power siwtch for the RPC. That is the little white square on/off button? The compuer seems to have lost its one.

Use a biro like everyone else. ;-)


--
Greg Harris (Norwich)

[Stuart Winsor]

In article <3f2030a8$1@news.iconz.co.nz>,
Henry Falkner <hfalkner@internet.co.nz> wrote: Hi there I ave a couple of question wrt to a RISC PC PSU (70W) I have here: It does not want to work! I have replaced the fuse, but when I connect it to a RPC mobo and HDD, the fan spins for about a quarter of a revolution and stop. And nothing else happens. Is there anything else I can do, or is this a problem for the big boys? Anybody else done fault diagnosis on RPC PSU's?


There have been loads of posts about repairing the 70W RPC PSU and the
Shottky diode that is the usual fault. Try google.

Stuart.

--
__ __ __ __ __ ___ _____________________________________________
|__||__)/ __/ \|\ ||_ | /
| || \\__/\__/| \||__ | /...Internet access for all Acorn RISC machines
___________________________/ stuartwinsor@argonet.co.uk

101 uses for a Pentium: No1 - A slow cooker.

[Samuel Kock]

In nuus:MPG.198a582823d865e698968a@news.demon.co.uk,
tik Greg <greg@nospam.demon.co.uk>: In article <bfok75$qvm$1@ctb-nnrp2.saix.net>, samuelk@depsammed.com says... Secondly, where can I find a power siwtch for the RPC. That is the little white square on/off button? The compuer seems to have lost its one. Use a biro like everyone else. ;-)

Uhm, total ignorance (bliss!), what is a biro?????

Samuel
--
Samuel Kock
Pretoria, South Africa
Bio: http://go.to/skock/bio.htm
Stability itself is nothing else than a more sluggish motion.

[Samuel Kock]

In nuus:4c2b34174c.steve@helvellyn.stevefryatt.org.uk,
tik Steve Fryatt <news@stevefryatt.org.uk>:
Try Googling this group for "RiscPC PSU diode" or something along those lines. There's a common failure mode due to an underrated output schottky diode, which should be fairly easy to diagnose and fix. If it isn't that, it could be more tricky to find.

Hmm, thanks! I have now gotten a few articles off google, will try and do
something about it soonish...
*However* (usual disclaimer), if you're not sure about power electronics, you may want to simply buy a replacement or get it fixed professionally. There are voltages up to 400Vdc inside the box, which may hold up longer than normal as the PSU isn't working properly. Give it at least several hours to discharge after unplugging it from the mains before removing the cover and take care.

It is OK, we know some people that are good at soldering and electronics and
such, so we will most probably take it to them. Besides, we dont have a
multimeter to test it.... :(..


Ciao!

Samuel

--
Samuel Kock
Pretoria, South Africa
Bio: http://go.to/skock/bio.htm
Stability itself is nothing else than a more sluggish motion.

[Jess]

In message <bfpins$irb$1@ctb-nnrp2.saix.net>
"skok" <samuelk@depsammed.com> wrote:
Uhm, total ignorance (bliss!), what is a biro?????

A disposable ballpoint pen (brand name like using hoover for vacuum
cleaner)

--
Jess icq: 91353267 msn: phantasm_39@hotmail.com http://www.kentwebnet.com
Hotmail is my spam trap - don't use for email
mailto:nospam@itworkshop.uklinux.net
RISC OS 4.36 kinetic 64+128+2M Castle Storm DMA + 17GB 586-133 I-3 ADSL


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----

[Samuel Kock]

In nuus:4c173d1401mfox@argonet.co.uk,
tik Martyn Fox <mfox@argonet.co.uk>: In article <bfpins$irb$1@ctb-nnrp2.saix.net>, skok <samuelk@depsammed.com> wrote: I'm not sure if that will mean the same in South Africa as it does in the UK but Hoover were one of the first manufacturers of vacuum cleaners and a vacuum cleaner is still often referred to as a "hoover" [1] and the process of cleaning as "hoovering".

HEre hoover is not that popular, we have Electrolux, "Nothing sucks like
Electrolux!" was a well used motto at some point. Especially if the said
vaccuum clearner broke :)
similarly, Biro were one of the first, if not /the/ first manufacturers of ballpoint pens with the result that some people still still refer to one as a "biro".

Ah, I see. Never heard of that make of pen over here. Now he said Parker,
that would have been another story... :)


Thx for the info!

Samuel
--
Samuel Kock
Pretoria, South Africa
Bio: http://go.to/skock/bio.htm
Look under the sofa cushion; you will be surprised at what you find.

[Dave Plowman]

In article <bfpitv$j15$1@ctb-nnrp2.saix.net>,
skok <samuelk@depsammed.com> wrote: Try Googling this group for "RiscPC PSU diode" or something along those lines. There's a common failure mode due to an underrated output schottky diode, which should be fairly easy to diagnose and fix. If it isn't that, it could be more tricky to find.
Hmm, thanks! I have now gotten a few articles off google, will try and do something about it soonish...

I've had the opto-isolator fail too.

--
*If they arrest the Energizer Bunny, would they charge it with battery? *

Dave Plowman dave.sound@argonet.co.uk London SW 12
RIP Acorn

[Hauke Wegner]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

In message <bfpn1l$ktb$1@ctb-nnrp2.saix.net>
"skok" <samuelk@depsammed.com> wrote:
In nuus:4c173d1401mfox@argonet.co.uk, tik Martyn Fox <mfox@argonet.co.uk>: In article <bfpins$irb$1@ctb-nnrp2.saix.net>, skok <samuelk@depsammed.com> wrote: I'm not sure if that will mean the same in South Africa as it does in the UK but Hoover were one of the first manufacturers of vacuum cleaners and a vacuum cleaner is still often referred to as a "hoover" [1] and the process of cleaning as "hoovering". HEre hoover is not that popular, we have Electrolux, "Nothing sucks like Electrolux!" was a well used motto at some point. Especially if the said vaccuum clearner broke :)

Vacuum cleaner seems to be an interesting theme in both the UK and
South Africa. However neither Hoover nor Electrolux are that popular
here.
similarly, Biro were one of the first, if not /the/ first manufacturers of ballpoint pens with the result that some people still still refer to one as a "biro". Ah, I see. Never heard of that make of pen over here. Now he said Parker, that would have been another story... :)

Do not mind about that. I am much closer to the UK but never heared
about "Biro" at all.



Sincerely Hauke
--
For eMail / Für E-Briefe : hw-privat @ 2a1p.de

Key fingerprint = B674 E173 327A E4DA CAD0 E360 1C36 367E 84F8 9BA5
http://www.2a1p.de <- RISC OS | Manga & Anime -> http://www.mang-a-nime.de
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2-sb1 (RISC OS)

iD8DBQE/IKLGHDY2foT4m6URAvSPAJ9QCuaV344AJjp1PEh1h0BSjztHnACgxjxN
CARcwaMeFbwJ0DNSap7bwlw=
=D9xO
-----END PGP SIGNATURE-----

[Dave Symes]

In article <a6fd58174c.NewsgroupUser@rpc01.2a1p.de>,
Hauke Wegner <newsgroupuser@2a1p.de> wrote:

[Snip]
Do not mind about that. I am much closer to the UK but never heared about "Biro" at all. Sincerely Hauke

Invented 1938 by Laslo Biro a Hungarian.

IIRC Went on general sale around 1946 ish.

The rest as they say is history.

Cheers
Dave S

--

[John Cartmell]

In article <a6fd58174c.NewsgroupUser@rpc01.2a1p.de>,
Hauke Wegner <newsgroupuser@2a1p.de> wrote: Do not mind about that. I am much closer to the UK but never heared about "Biro" at all.
Ladislao Jose Biro
1899-1985
Hungarian inventor. Wokring with a magazine, he realized the advantage of
quick-drying ink, and in 1940 went to Argentina with his ideas for
developing a ballpoint pen, which eventually became a great success (the
biro).
from the Cambridge Biographical Encyclopedia

...and Biros were amongst the best ordinary ballpoint pens available but I
don't remember having seen one for some time.

--
John Cartmell john@cartmell.demon.co.uk FAX +44 (0)8700-519-527
Acorn Publisher magazine & FD Games www.acornpublisher.com

[Samuel Kock]

In nuus:4c173ff47cdave.sound@argonet.co.uk,
tik Dave Plowman <dave.sound@argonet.co.uk>: In article <bfpitv$j15$1@ctb-nnrp2.saix.net>, skok <samuelk@depsammed.com> wrote: Try Googling this group for "RiscPC PSU diode" or something along those lines. There's a common failure mode due to an underrated output schottky diode, which should be fairly easy to diagnose and fix. If it isn't that, it could be more tricky to find. Hmm, thanks! I have now gotten a few articles off google, will try and do something about it soonish... I've had the opto-isolator fail too.

Hmm, where is that on the PCB?

Samuel
--
Samuel Kock
Pretoria, South Africa
Bio: http://go.to/skock/bio.htm
A journey of a thousand miles must begin with a single step.

[Tim Powys-Lybbe]

In message <4c17756fe8john@cartmell.demon.co.uk>
John Cartmell <john@cartmell.demon.co.uk> wrote:
In article <a6fd58174c.NewsgroupUser@rpc01.2a1p.de>, Hauke Wegner <newsgroupuser@2a1p.de> wrote: Do not mind about that. I am much closer to the UK but never heared about "Biro" at all. Ladislao Jose Biro 1899-1985 Hungarian inventor. Wokring with a magazine, he realized the advantage of quick-drying ink, and in 1940 went to Argentina with his ideas for developing a ballpoint pen, which eventually became a great success (the biro). from the Cambridge Biographical Encyclopedia

I remember my mother being grossly extravagant what seems like soon
after the war and buying one of these new fangled things for a whole 3
ukp with the information that it would still work five miles up in an
aeroplane.
..and Biros were amongst the best ordinary ballpoint pens available but I don't remember having seen one for some time.

I think BIC was the successor brand name.

--
Tim Powys-Lybbe tim@powys.org
For a miscellany of bygones: http://powys.org

[Hauke Wegner]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

In message <56a593174c.tim@south-frm.demon.co.uk>
Tim Powys-Lybbe <tim@powys.org> wrote:
In message <4c17756fe8john@cartmell.demon.co.uk>

[snip]
..and Biros were amongst the best ordinary ballpoint pens available but I don't remember having seen one for some time. I think BIC was the successor brand name.

I know this brand name. But not for ballpen or anything like that but
for cheap lighters.


Sincerely Hauke
--
For eMail / Für E-Briefe : hw-privat @ 2a1p.de

Key fingerprint = B674 E173 327A E4DA CAD0 E360 1C36 367E 84F8 9BA5
http://www.2a1p.de <- RISC OS | Manga & Anime -> http://www.mang-a-nime.de
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2-sb1 (RISC OS)

iD8DBQE/IUdFHDY2foT4m6URAl7QAKCUsBZLff/rE6Vp/ktoRkmnxQxE4QCfeAD3
HtSjSwijClRxqf2Fu+azBnQ=
=pXZn
-----END PGP SIGNATURE-----

[Martyn Fox]

In article <5f3f99174c.NewsgroupUser@rpc01.2a1p.de>, Hauke Wegner
<newsgroupuser@2a1p.de> wrote:
I think BIC was the successor brand name.
I know this brand name. But not for ballpen or anything like that but for cheap lighters.

It's probably the most prolific name in the UK for cheap, disposable
ball-point pens.

I posed a question to several colleagues at work and they all came up with
the same answer as I would have given:

"If you were to go away from your desk for a few minutes and you left a
wristwatch and a cheap company ball-point pen on your desk, which would be
more likely still to be there when you came back?"

All agreed that the watch would be more likely to be there.

Martyn

--
_
|\/| _ _ -+- _ |_ _ Windsor, Berks. UK
| | (_| | | (_| | ) | (_) )( mfox@argonet.co.uk
ZFC La _| Iyonix pc with 80321 and RISC OS - a Windoze-free zone!

[Simon Willcocks]

In message <4c179cac77mfox@argonet.co.uk>
Martyn Fox <mfox@argonet.co.uk> wrote:
I posed a question to several colleagues at work and they all came up with the same answer as I would have given: "If you were to go away from your desk for a few minutes and you left a wristwatch and a cheap company ball-point pen on your desk, which would be more likely still to be there when you came back?" All agreed that the watch would be more likely to be there.

I think that depends where you work! I wouldn't be surprised if a colleague
snatched a cheap biro from my desk to scribble something down and forgot to
return it; I would be very surprised if any of them would steal anything.
(I regularly left my Psion on my desk, even when it was still worth a fair
percentage of the several hundred pounds it cost.)

Simon