2 Oct
2013
2 Oct
'13
7:52 a.m.
So I have recently been given half a dozen Acorns - one Model A, 4
Model B+ with 64K and one 128K B+.
I'm going to donate the Model A, at least, to TNMOC at Bletchley, but
I'd like to keep at least one for myself.
The thing is, whereas I wouldn't just turn on a 1980s business
computer with multiple moving parts, the donations chap at TNMOC has
put The Fear into me by sternly warning me Not To Turn Any Of Them On,
because They Will Blow Up.
So, how does one go about testing a mucky old Beeb that's not been on
in 25y or something & has been stored in a dusty attic?
Give it a good clean, I guess, but can one hook one to a PC PSU and
test its internal PSU in isolation?
--
Liam Proven ? Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884
2 Oct
2 Oct
9:54 a.m.
Liam Proven <lproven at gmail.com> writes:
[...] the donations chap at TNMOC has put The Fear
into me by sternly
warning me Not To Turn Any Of Them On, because They Will Blow Up.
That's a bit over-the-top. But more or less accurate. ;-)
The explosion in question is the result of the power supply's mains
filter capacitors suffering from perished plastic after 30-odd years. If
you run an old BBC for a while without replacing them, you'll eventually
get a quiet "pop" and a cloud of evil-smelling smoke. The machine will
actually continue to work just fine, but the EMC performance is
presumably somewhat degraded, and you'll want to scrape all the bits of
exploded capacitor out to get rid of the smell.
Sprow's BBC repair FAQ has a section on replacing these, which is quite
straightforward -- it's awkward enough to get into the power supply that
you may as well replace the other parts he suggests (all available from
CPC or a similar electronics supplier) at the same time:
http://www.sprow.co.uk/bbc/howto.htm#powersupply
Note that the same power supply board is used in some BBC Micro disk
drives; I've got a Watford dual drive which had exactly the same
problem.
Other than that, I've found BBCs to be extremely reliable; I've cleaned
up several for friends over the last few years and only found one that
didn't boot first time (because somebody had stolen the disk controller
chip and not adjusted the jumpers to suit).
Don't forget to check your machines to see if they've got any
interesting sideways ROMs in!
Thanks,
--
Adam Sampson <ats at offog.org> <http://offog.org/>
10:05 a.m.
On 2 October 2013 17:54, Adam Sampson <ats at offog.org> wrote:
That's a bit over-the-top. But more or less accurate. ;-)
The explosion in question is the result of the power supply's mains
filter capacitors suffering from perished plastic after 30-odd years. If
you run an old BBC for a while without replacing them, you'll eventually
get a quiet "pop" and a cloud of evil-smelling smoke. The machine will
actually continue to work just fine, but the EMC performance is
presumably somewhat degraded, and you'll want to scrape all the bits of
exploded capacitor out to get rid of the smell.
Sprow's BBC repair FAQ has a section on replacing these, which is quite
straightforward -- it's awkward enough to get into the power supply that
you may as well replace the other parts he suggests (all available from
CPC or a similar electronics supplier) at the same time:
http://www.sprow.co.uk/bbc/howto.htm#powersupply
Note that the same power supply board is used in some BBC Micro disk
drives; I've got a Watford dual drive which had exactly the same
problem.
Other than that, I've found BBCs to be extremely reliable; I've cleaned
up several for friends over the last few years and only found one that
didn't boot first time (because somebody had stolen the disk controller
chip and not adjusted the jumpers to suit).
Don't forget to check your machines to see if they've got any
interesting sideways ROMs in!
That's excellent and very helpful - thank you!
JOOI, as a separate problem...
If one had a BBC B+ (which AIUI means, amongst other things, built-in
DFS (possibly upgraded to ADFS)), and a floppy drive, but no disks at
all, how would on go about bootstrapping it to the point where it
could write floppy disks?
I am told that DFS doesn't contain a routine to format floppies. I
have blank media and I have a working PC with a 5.25" 80-track
high-density ("1.2MB") drive which has both MS-DOS and Linux running
on it.
The Linux is currently Ubuntu 12.04, 32-bit. Other (older) versions
could be arranged.
And somewhere I have copies of 22disk and things like that, but I have
no idea if the media still work.
I came into the Acorn world with the Archimedes, which meant 3.5"
media and an OS which could [a] format its own disks unaided and [b]
could read/write PC-format media. I've never had to try
reading/writing Acorn media on PCs.
--
Liam Proven ? Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884
12:26 p.m.
Liam Proven <lproven at gmail.com> writes:
I am told that DFS doesn't contain a routine to
format floppies.
That's true for the common Acorn DFS, but you may of course be lucky and
find that you've got a better DFS (e.g. the Watford one) or a utility
ROM with a format command in one of your machines -- try *HELP.
Failing that, J. G. Harston has a neat little format program that's
short enough to type in:
http://mdfs.net/Software/BBC/FormDFS.txt
Note also that if you've got a serial cable, you can easily make the BBC
accept input from the serial port as if you'd typed it (*FX 7,6 and *FX
8,6 to receive/transmit 4800 baud, then *FX 2,2 to receive from the
serial port), so you can get large BASIC programs over to the machine.
XFer is a good candidate for this since it lets you transfer disk images
back and forth over the serial link. One version's available from here:
http://regregex.bbcmicro.net/
I have blank media and I have a working PC with a
5.25" 80-track
high-density ("1.2MB") drive which has both MS-DOS and Linux running
on it.
DFS format is FM with 10 256-byte sectors, so you should be able to
format and write a disk with ImageDisk or similar. Here's an ImageDisk
file of an 80T DFS disk:
http://offog.org/stuff/bbc-80t.imd
I'm not sure if writing with an HD drive will cause any problems for
your BBC's drive reading it, but if so then you may be able to connect
your BBC floppy drive to your PC -- I had to fiddle the jumpers on my
Mitsubishi MF503A 80T drive to make the disk change signal active low
when connecting it to a PC.
You may also enjoy the bbc-micro mailing list:
http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
Thanks,
--
Adam Sampson <ats at offog.org> <http://offog.org/>
2:23 p.m.
On 2 October 2013 20:26, Adam Sampson <ats at offog.org> wrote:
I could try that - I have some near-identical Spectrum drives, too:
80t DS/DD with Shugart interfaces. I've managed to drive a 5.25"
DS/DD from a PC before, I think.
Very few of my PCs have floppy controllers any more though. I think
there's one left.
Liam Proven <lproven at gmail.com> writes:
Ha. It figures. I have just last month given away all my old serial
cables, sent for recycling in a big clearout.
I am told that DFS doesn't contain a routine
to format floppies.
That's true for the common Acorn DFS, but you may of course be lucky and
find that you've got a better DFS (e.g. the Watford one) or a utility
ROM with a format command in one of your machines -- try *HELP.
Failing that, J. G. Harston has a neat little format program that's
short enough to type in:
http://mdfs.net/Software/BBC/FormDFS.txt
Note also that if you've got a serial cable, you can easily make the BBC
accept input from the serial port as if you'd typed it (*FX 7,6 and *FX
8,6 to receive/transmit 4800 baud, then *FX 2,2 to receive from the
serial port), so you can get large BASIC programs over to the machine.
XFer is a good candidate for this since it lets you transfer disk images
back and forth over the serial link. One version's available from here:
http://regregex.bbcmicro.net/ I have blank
media and I have a working PC with a 5.25" 80-track
high-density ("1.2MB") drive which has both MS-DOS and Linux running
on it.
DFS format is FM with 10 256-byte sectors, so you should be able to
format and write a disk with ImageDisk or similar. Here's an ImageDisk
file of an 80T DFS disk:
http://offog.org/stuff/bbc-80t.imd
I'm not sure if writing with an HD drive will cause any problems for
your BBC's drive reading it, but if so then you may be able to connect
your BBC floppy drive to your PC -- I had to fiddle the jumpers on my
Mitsubishi MF503A 80T drive to make the disk change signal active low
when connecting it to a PC. You may also enjoy the bbc-micro mailing list:
http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
Better still.
Thanks very much!
--
Liam Proven ? Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884
3:05 p.m.
> DFS format is FM with 10 256-byte sectors, so you
should be able to
> format and write a disk with ImageDisk or similar. Here's an ImageDisk
> file of an 80T DFS disk:
> http://offog.org/stuff/bbc-80t.imd
On Wed, 2 Oct 2013, Liam Proven wrote:
Very few of my PCs have floppy controllers any more
though. I think
there's one left.
If it IS 10 256 byte sectors, then it is FM/SINGLE DENSITY.
There are SOME PC disk controllers that can handle that, many more that
can not. Dave has some utilities for testing that.
If it IS 80 tracks per side, then you will need a 96tpi drive, preferrably
"720K", but "1.2M" can usually made to work, NOT A "360K"
drive.
If it is 40 cylinders with 2 sides, then that would, indeed ALSO be
referrable to as "80 track" IFF you WANT to be ambiguous.
For formatting blank disks, . . .
TRS80 [model 1] was 35 track/35 cylinder single sided with 10 x 256.
Osborne was 40 track/40 cylinder single sided with 10 x 256.
Both are 48tpi.
If you have 96tpi, then track 0 would be in the same place
That doesn't solve the formatting problem, but, if the error messages are
specific enough to differentiate between unformatted disk ("General
Failure" in PC), versus formatted, but can't find the disered sector
("Sector Not Found" in PC) then that may provide some further diagnostic
info.
3 Oct
3 Oct
10:54 a.m.
If it IS 10 256 byte sectors, then it is FM/SINGLE
DENSITY.
There are SOME PC disk controllers that can handle that, many more that
can not. Dave has some utilities for testing that.
It is single-density.
The original BBC micro came in Model A and Model B versions. Both usd the
smae PCB, the 'A' had fewer ICs fitted. Often the empty spaces in an 'A'
were fitted with DIL sockets, which cost almost as much as the missing
ICs. Go figure...
Anyway, neither had a disk controler as standard. It was an option, a
handful of ICs to plug into the main PCB. The actual disk controller chip
was an Intel 8271 (no, I do not mean 8272), which was single density
only. The same IC had been used on the earlier 'System' machines made on
multiple Eurocards.
For various reaoons, later models used a 1770 disk controller. This could
be fitted to the Model A/Model B in the form of a daughterboard that went
in the 8271 socket. The B+ and Master (and machines baded on them, like
the ABC and ACW) all have a 1770. This supports single and double density.
The firmware (known as 'DFS' -- Disk Filing System) is different for the
8271 and 1770 controllrs. IIRC there is a routine in the 1770 DFS to
accept 8271 commands and convert them to 1770 commands so that
copy-protected software that did odd things to the disk controller, would
still run. I seem to rememebr that ADFS (Advvanced Disk FIling System)
needs a 1770. I also seem to rememebr that ADFS will do MFM, -lain DFS --
even the 1770 version -- is FM (single density) only.
If it IS 80 tracks per side, then you will need a 96tpi drive, preferrably
"720K", but "1.2M" can usually made to work, NOT A "360K"
drive.
If it is 40 cylinders with 2 sides, then that would, indeed ALSO be
referrable to as "80 track" IFF you WANT to be ambiguous.
Beebs support 40 and 80- cylidner drives. DFS treats all disks as
single-sided, if you have a double-head drive, the 2 sifes are different
disks to the system, ADFS also supports 40 and 80 cylidner drives, I
can't remembr how it handles 2 sides.
-tony
10:41 a.m.
Note also that
if you've got a serial cable, you can easily make the BBC
accept input from the serial port as if you'd typed it (*FX 7,6 and *FX
8,6 to receive/transmit 4800 baud, then *FX 2,2 to receive from the
serial port), so you can get large BASIC programs over to the machine.
XFer is a good candidate for this since it lets you transfer disk images
back and forth over the serial link. One version's available from here:
http://regregex.bbcmicro.net/
Ha. It figures. I have just last month given away all my old serial
cables, sent for recycling in a big clearout. 
4 Oct
4 Oct
4:20 p.m.
On Thu, 3 Oct 2013, Tony Duell wrote:
The serial cable for the BBC Micro could be something
of a problem. The
serial port socket on the Beeb is the 'RS423' port on the back, this can
be connected to a nromal RS232 port with no electronic circuitry. The
problem is the connector itself. It's one of thsoe 5 pin quincuncial DIN
plugs (also known as a 'tpye C, 270 degree, 360 degree, or 'domino' 5 pin
DIN plug). Is it nor the much more common 180 degree Tpye A or 240 degree
type B one.
This leads to 2 problems :
1) The plug is getting very hard ot find. Maplin don't list it.
Crickelewood electronics have the sockets but not the plugs (I guess they
are selling off old stock). RS Components have discontinued it. Farnell
still list it, but I don't know if they will be stocking it in the future.
2) DIN plgus are not easy to solder. They are one mf my least favourite
ocnnectors in this respect (OK, mini-DIN are much worse...). The normal
DIN plug pins do not take solder easily. And the plastic insualtor melts
far too easily. I suspect from what you have said before that you might
have rather more problems.
The key thing I've found essential for soldering these is liquid flux.
Having a spare socket to plug the connector into helps (in case you don't
"touch and go"), but a small amount of RMA liquid flux allows the solder
to take quickly. Very small diameter solder (0.015" to 0.025") is also
important to have, especially when dealing with the mini-DIN variety.
5 Oct
5 Oct
11:50 a.m.
The key thing I've found essential for soldering
these is liquid flux.
Interesting. I've never tried that.
Having a spare socket to plug the connector into helps
(in case you don't
"touch and go"), but a small amount of RMA liquid flux allows the solder
Yes, holdign he pin assembly is not easy. I have a small vice on my
electronics bench for hold stuff I am soldering, but of course it just
holds circular objects at 2 points. So it;s not that rigid. I have been
known to mound a spare socket of the right type on a block of wood or
plastic and clamp that in the vice
to take quickly. Very small diameter solder
(0.015" to 0.025") is also
important to have, especially when dealing with the mini-DIN variety.
Sure..
Try soldering a 9 pin mini-DIN and then having to swap round 2 wires on
the centre row of pins. This acutally happened to me, the 9 pin mini-DI
Nsi used as the mouse connector on the Acorn Archimedes, I was wiring up
a spare qudrature mouse as I didn't have the Acorn one. Of course I got
at least one of the 2 axes moving backwards on the first try, meaning I
had to swap roudn that pair of signals.
Anyway, my original comment about wiring DIN plugs was realy aimed at
Liam, who started this trhread. He has said several times that he does
not enjoy sodlering. I don't wish to insult him, but I do think he would
ahve problems wiring a DIN plug.
-tony
5:14 p.m.
?
----- Original Message -----
From: "General Discussion: On-Topic Posts Only"
To:"General Discussion: On-Topic and Off-Topic Posts"
Cc:
Sent:Fri, 4 Oct 2013 18:20:00 -0500 (CDT)
Subject:Re: Reviving elderly BBC Micros
On Thu, 3 Oct 2013, Tony Duell wrote:
The serial cable for the BBC Micro could be something
of a problem
The
serial port socket on the Beeb is the 'RS423'
port on the back,
this can
be connected to a nromal RS232 port with no electronic
circuitry.
The
problem is the connector itself. It's one of thsoe
5 pin
quincuncial DIN
plugs (also known as a 'tpye C, 270 degree, 360
degree, or 'domino'
5 pin
DIN plug). Is it nor the much more common 180 degree
Tpye A or 240
degree
type B one.
This leads to 2 problems :
1) The plug is getting very hard ot find. Maplin don't list it.
Crickelewood electronics have the sockets but not the plugs (I
guess they
are selling off old stock) RS Components have
discontinued it.
Farnell
still list it, but I don't know if they will be
stocking it in the
future.
2) DIN plgus are not easy to solder. They are one mf my least
favourite
ocnnectors in this respect (OK, mini-DIN are much
worse...). The
normal
DIN plug pins do not take solder easily. And the
plastic insualtor
melts
far too easily. I suspect from what you have said
before that you
might
have rather more problems.
The key thing I've found essential for soldering these is liquid
flux.
Having a spare socket to plug the connector into helps (in case you
don't
"touch and go"), but a small amount of RMA liquid flux allows the
solder
to take quickly. Very small diameter solder (0.015" to 0.025") is
also
important to have, especially when dealing with the mini-DIN variety.
2 Oct
2 Oct
12:52 p.m.
So I have recently been given half a dozen Acorns - one Model A, 4
Model B+ with 64K and one 128K B+.
I'm going to donate the Model A, at least, to TNMOC at Bletchley, but
I'd like to keep at least one for myself.
The thing is, whereas I wouldn't just turn on a 1980s business
computer with multiple moving parts, the donations chap at TNMOC has
put The Fear into me by sternly warning me Not To Turn Any Of Them On,
because They Will Blow Up.
Tht's going a bit far. It is a very bad idea to jsut power on any old
computer, but they don't _always_ blow up.
So, how does one go about testing a mucky old Beeb that's not been on
in 25y or something & has been stored in a dusty attic?
Give it a good clean, I guess, but can one hook one to a PC PSU and
test its internal PSU in isolation?
Yes.
The BBC PSU is a separate unit. It links to the mainboard with 7 wires
IIRC. The 3 black ones are all ground (0V). The 3 red ones are all +5V.
And the other one (purple?) is -5V. Actually, IIRC the Beeb will run (but
sound doesn't work) with only a +5V supply.
There are at least 2 versions of the Beeb PSU The origianl one (in a
black case IIRC) was a linear supply. A mains transformer and 3 separae
5V regulators. This oen was well-known for takign the varnish off tables,
it ran so hot. Most were replaced by the later one, so this supply is
now very rare. If you have one, hang on to it (but don't run it!). IIRC
the 3 red wires are acutally separate 5V outputs, one form each regulator.
The laster PSU in an off-silver case was an Astec switch-mode unit. With
that one., there is on 5V output, conencted to the 3 red wires.
I _think_ very early revsion mainboards have 3 separate 5V connecitons,
one for each PSU output, each feeding soem of the chips. On later boards,
all 3 5V tags are connected together. It is still a good idea to connect
to all 3 tags when testing, the current drawn is ratehr too much for just
one connection.
So what I would do :
With the machine unplugged from the mains, take off the cover and
keyboard. Then disconnect all 7 PSU wires (the -5V one is difficult to
spot, it's in the corner near the PSU). Tkae the PSU out (3 screws o nthe
bottom. Removeing the mainboard from a Beeb is not as easy as it might
be, IIRC you have to desodler the wires to the video output BNC socket.
Inpsect the PSU for burnt components, bulging or physically
leakingcapoacitors, etc. Check the fuse is good and the right rating.
Put the PSU back in place but do not connect the wires ot the mainboard.
Connect a 6V 6W bulb (or thereabouts) between one fo the red wires nad
one of the black wires (assuming this is the later SMPSU, I can explains
what to do with the linear one if you really have that one). Power up,
the bulb should light. Check you have 5V across it.
If you can't get the bulb, then a 4.7 Ohm 10W resistor would also be a
suitable load. That might be easier to find.
If so, then power down, reconnect the wires -- correcrtly -- to the
mainboard, connect up the keyboard, and try the machine out.
-tony
2:25 p.m.
On 2 October 2013 20:52, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Many thanks, Tony! I think that between Peter Corlett and I, we can do that.
--
Liam Proven ? Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884
So I have recently been given half a dozen Acorns - one Model A, 4
Model B+ with 64K and one 128K B+.
I'm going to donate the Model A, at least, to TNMOC at Bletchley, but
I'd like to keep at least one for myself.
The thing is, whereas I wouldn't just turn on a 1980s business
computer with multiple moving parts, the donations chap at TNMOC has
put The Fear into me by sternly warning me Not To Turn Any Of Them On,
because They Will Blow Up.
Tht's going a bit far. It is a very bad idea to jsut power on any old
computer, but they don't _always_ blow up.
So, how does one go about testing a mucky old Beeb that's not been on
in 25y or something & has been stored in a dusty attic?
Give it a good clean, I guess, but can one hook one to a PC PSU and
test its internal PSU in isolation?
Yes.
The BBC PSU is a separate unit. It links to the mainboard with 7 wires
IIRC. The 3 black ones are all ground (0V). The 3 red ones are all +5V.
And the other one (purple?) is -5V. Actually, IIRC the Beeb will run (but
sound doesn't work) with only a +5V supply.
There are at least 2 versions of the Beeb PSU The origianl one (in a
black case IIRC) was a linear supply. A mains transformer and 3 separae
5V regulators. This oen was well-known for takign the varnish off tables,
it ran so hot. Most were replaced by the later one, so this supply is
now very rare. If you have one, hang on to it (but don't run it!). IIRC
the 3 red wires are acutally separate 5V outputs, one form each regulator.
The laster PSU in an off-silver case was an Astec switch-mode unit. With
that one., there is on 5V output, conencted to the 3 red wires.
I _think_ very early revsion mainboards have 3 separate 5V connecitons,
one for each PSU output, each feeding soem of the chips. On later boards,
all 3 5V tags are connected together. It is still a good idea to connect
to all 3 tags when testing, the current drawn is ratehr too much for just
one connection.
So what I would do :
With the machine unplugged from the mains, take off the cover and
keyboard. Then disconnect all 7 PSU wires (the -5V one is difficult to
spot, it's in the corner near the PSU). Tkae the PSU out (3 screws o nthe
bottom. Removeing the mainboard from a Beeb is not as easy as it might
be, IIRC you have to desodler the wires to the video output BNC socket.
Inpsect the PSU for burnt components, bulging or physically
leakingcapoacitors, etc. Check the fuse is good and the right rating.
Put the PSU back in place but do not connect the wires ot the mainboard.
Connect a 6V 6W bulb (or thereabouts) between one fo the red wires nad
one of the black wires (assuming this is the later SMPSU, I can explains
what to do with the linear one if you really have that one). Power up,
the bulb should light. Check you have 5V across it.
If you can't get the bulb, then a 4.7 Ohm 10W resistor would also be a
suitable load. That might be easier to find.
If so, then power down, reconnect the wires -- correcrtly -- to the
mainboard, connect up the keyboard, and try the machine out. 
2:50 p.m.
The thing is, whereas I wouldn't just turn on a
1980s business
computer with multiple moving parts, the donations chap at TNMOC has
put The Fear into me by sternly warning me Not To Turn Any Of Them On,
because They Will Blow Up.
Well, In my years of doing this hobby I've literally powered up about 30+ old
computers of about the same age as the BBC or older, and in that time I've only ever
had a single blown cap in a single power supply. The worst part of it was the smell. The
bang was a little shocking, but nothing to freak out about. I would just recommend you
stay close to the on/off switch at the mains.
Phil
3 Oct
3 Oct
10:44 a.m.
The thing is, whereas I wouldn't just turn on
a 1980s business
computer with multiple moving parts, the donations chap at TNMOC has
put The Fear into me by sternly warning me Not To Turn Any Of Them On,
because They Will Blow Up.
Well, In my years of doing this hobby I've literally powered up about 30+ o=
ld computers of about the same age as the BBC or older, and in that time I'=
ve only ever had a single blown cap in a single power supply. The worst par=
t of it was the smell. The bang was a little shocking, but nothing to freak=
out about. I would just recommend you stay close to the on/off switch at t=
he mains.
4047
days inactive
4051
days old
14 comments
7 participants
participants (7)
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ard＠p850ug1.demon.co.uk -
ats＠offog.org -
cisin＠xenosoft.com -
dgreen＠iinet.net.au -
lproven＠gmail.com -
philip＠neoncluster.com -
tothwolf＠concentric.net