17 May
2009
17 May
'09
4:20 a.m.
Title says it all; rescued a Color Classic from Certain Doom, but the
motherboard is beyond repair (somehow it's all rusted and nasty while
the rest of the machine is clean as a whistle...)
Anyone have a working spare to part with (or know a good place to get
one cheap?)
Thanks as always...
Josh
17 May
17 May
4:39 a.m.
Title says it all; rescued a Color Classic from
Certain Doom, but the
motherboard is beyond repair (somehow it's all rusted and nasty while
the rest of the machine is clean as a whistle...)
Anyone have a working spare to part with (or know a good place to get
one cheap?)
That is probably hard to come by (and you can't have mine :) but I am
told you can replace it with a Performa 275 or 550 (although the rear
port cover may not necessarily match up).
Alternatively, turn it into a Mystic with an LC 570-series board; see
http://www.colourclassicfaq.com/mobo/roadmap.html
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
-- Why was I born with such contemporaries? -- Oscar Wilde --------------------
4:43 a.m.
That is probably hard to come by (and you can't
have mine :) but I am
told you can replace it with a Performa 275 or 550 (although the rear
port cover may not necessarily match up).
And, just in case it wasn't clear, a Performa 250 would be an exact match
;-) but I actually have seen more CCs than I've seen P250s.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
-- This message will self-destruct in five seconds. Good luck, Jim. -- M:I ----
4:45 a.m.
As already discussed heavily on the list, it's probably due to the
battery corroding/erupting over time. The Mac Color Classic I got my
hands on was the same way. Since I really had nothing to lose, I took
the easy approach of actually just washing the board under water. Once
dried and reassembled it worked.
There were much more elegant approaches on how you might repair such
damages on the list. Might be worth a look.
Josh Dersch wrote:
Title says it all; rescued a Color Classic from
Certain Doom, but the
motherboard is beyond repair (somehow it's all rusted and nasty while
the rest of the machine is clean as a whistle...)
Anyone have a working spare to part with (or know a good place to get
one cheap?)
Thanks as always...
Josh
5:26 a.m.
Michael Lee wrote:
As already discussed heavily on the list, it's
probably due to the
battery corroding/erupting over time. The Mac Color Classic I got my
hands on was the same way. Since I really had nothing to lose, I took
the easy approach of actually just washing the board under water.
Once dried and reassembled it worked.
There were much more elegant approaches on how you might repair such
damages on the list. Might be worth a look.
It's not battery corrosion -- the board is literally rusted, all over
:). The battery's nasty too, but that's only a small part of what's
wrong with it. I suppose I can soak it in something, maybe scrub it
with a toothbrush and see if that helps at all, but it's pretty bad.
As Cameron pointed out, there are other boards that will work with some
modification, I'll keep my eyes out for those as well...
Thanks,
Josh
Josh Dersch wrote:
Title says it all; rescued a Color Classic from
Certain Doom, but the
motherboard is beyond repair (somehow it's all rusted and nasty while
the rest of the machine is clean as a whistle...)
Anyone have a working spare to part with (or know a good place to get
one cheap?)
Thanks as always...
Josh
5:51 a.m.
New subject: Apple II Plus power supply strangeness
I've had a little more time to poke at the Apple II Europlus. It's a
240V model - reason I mention that is that the power supply is doing
strange things. If I power it up with no cards, it will do nothing for a
minute or so. Looking closely, the power light glows very dimly; the +5V
PS line is sitting at about 1V or so. After a little time, the supply
will suddenly come up completely, and the machine will work perfectly
and pass all tests for maybe 30 seconds, after which the memory slowly
becomes more and more corrupt.
If, while the PS is not running correctly, I hit the Reset button, that
will kick it into life. Odd, but I guess Reset lowers the load on the
PS, allowing it to start properly.
My intention is to replace all the caps on the output side of the PS. In
the meantime, does anyone have any insights into why a power supply
might behave in this way? Seems odd to me, though my understanding of
switch-mode power supply theory doesn't stretch terribly far.
Mike.
5:58 p.m.
New subject: Apple II Plus power supply strangeness
I've had a little more time to poke at the Apple II Europlus. It's a
240V model - reason I mention that is that the power supply is doing
strange things. If I power it up with no cards, it will do nothing for a
minute or so. Looking closely, the power light glows very dimly; the +5V
PS line is sitting at about 1V or so. After a little time, the supply
I am assuming this PSU is similar to the one shown on page 93 of the
reference manual. According to said manual, the PSU is covered by US
patent 4130862. I have no idea what that patent describes, but it might
be worth a look (although I doubt it'll be as useful as some of the old
HP patents...)
This PSU seems to have a crowbar circuit (SCR Q5, zener CR20, etc), but
amazingly it seems to be connected to the 12V output. This is, IMHO,
ridiculous. When a PSU output sits at about 1V, I often suspect that a
crowbar is triggereing, which will shut the supply down, thus enabling
the crowbar to turn off, the cycle then repeats. So what you see is an
average of the 'too high' and 'shorted' output voltages.
If the output capacitors have high ESR (a likely problem due to old age),
there will be spikes on the output, sometimes around twice the normal
output votlage. These will trip the crowbar, of course.
I have no idea why pressing reset makes any difference. I guess it is a
change in load
-tony
6:28 p.m.
New subject: Apple II Plus power supply strangeness
here is the link to the us patent office website for that number
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d…
On 5/17/09, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I've had a little more time to poke at the Apple II Europlus. It's a
240V model - reason I mention that is that the power supply is doing
strange things. If I power it up with no cards, it will do nothing for a
minute or so. Looking closely, the power light glows very dimly; the +5V
PS line is sitting at about 1V or so. After a little time, the supply
I am assuming this PSU is similar to the one shown on page 93 of the
reference manual. According to said manual, the PSU is covered by US
patent 4130862. I have no idea what that patent describes, but it might
be worth a look (although I doubt it'll be as useful as some of the old
HP patents...)
This PSU seems to have a crowbar circuit (SCR Q5, zener CR20, etc), but
amazingly it seems to be connected to the 12V output. This is, IMHO,
ridiculous. When a PSU output sits at about 1V, I often suspect that a
crowbar is triggereing, which will shut the supply down, thus enabling
the crowbar to turn off, the cycle then repeats. So what you see is an
average of the 'too high' and 'shorted' output voltages.
If the output capacitors have high ESR (a likely problem due to old age),
there will be spikes on the output, sometimes around twice the normal
output votlage. These will trip the crowbar, of course.
I have no idea why pressing reset makes any difference. I guess it is a
change in load
-tony
18 May
18 May
10:35 a.m.
New subject: Apple II Plus power supply strangeness
Tony Duell wrote:
This PSU seems to have a crowbar circuit (SCR Q5,
zener CR20, etc), but
amazingly it seems to be connected to the 12V output. This is, IMHO,
ridiculous.
I have a few ideas as to why it could be considered a bad thing, but
I'd be interested to hear more details!
When a PSU output sits at about 1V, I often suspect
that a
crowbar is triggereing, which will shut the supply down, thus enabling
the crowbar to turn off, the cycle then repeats. So what you see is an
average of the 'too high' and 'shorted' output voltages.
OK - I'll check the outputs with the oscilloscope when it's in that
mode, and see if I can see a waveform that looks like that.
If the output capacitors have high ESR (a likely
problem due to old age),
there will be spikes on the output, sometimes around twice the normal
I've grabbed new replacements for all the capacitors, apart from the big
high-voltage input-side ones. One of the output capacitors has shrunk
its heat-shrink wrapping quite considerably, so I'm guessing that one
has been running quite hot. Might as well replace them all though - the
replacements only cost me NZ$10 (something like 3 pounds, maybe US$5, at
a guess) so it's hardly breaking the bank.
Once I have the power supply behaving more sanely, I'll feel more
confident in trying to track down any further logic board problems.
Thanks for the suggestions, and also to Chris H for the patent info. I
haven't had a chance to read it in depth yet, but I will.
Mike
12:05 p.m.
New subject: Apple II Plus power supply strangeness
I've grabbed new replacements for all the
capacitors, apart from the
big high-voltage input-side ones. One of the output capacitors has
shrunk its heat-shrink wrapping quite considerably, so I'm guessing
that one has been running quite hot. Might as well replace them all
though - the replacements only cost me NZ$10 (something like 3 pounds,
maybe US$5, at a guess) so it's hardly breaking the bank.
Be careful with the high voltage ones in the input filter before the
diode rectifier. (A couple of uF, 400 or so volts AC rated - encased in
a clear plastic case) I had an apple 2 recently that had one of these
fail spectacularly - tons of brown goo that smelt of cigarette smoke
(tar?) spewed forth. It was hard to remove. But It is happier now.
Also - regarding the drop the 12V rail - isn't that the one that is
monitored to regulate the switcher?
Does anybody have the schematic for these PSUs?
Doug
5:59 p.m.
New subject: Apple II Plus power supply strangeness
Be careful with the high voltage ones in the input
filter before the
diode rectifier. (A couple of uF, 400 or so volts AC rated - encased in
a clear plastic case) I had an apple 2 recently that had one of these
Mains filter capacitors (these are the non-polarised ones, AC rated,
connected across the power lien, or from one side of the power line to
earth) often fail spectacularly, but do no further damage. They are
certainly not the cause of any output-side problems.
fail spectacularly - tons of brown goo that smelt of
cigarette smoke
(tar?) spewed forth. It was hard to remove. But It is happier now.
Also - regarding the drop the 12V rail - isn't that the one that is
monitored to regulate the switcher?
The 12V line powers part of the regualtor circuit (on the schematic I
have, it's based round Q4 and AR1 -- AR1 is an optoisolator, and the LED
secion appears to be drawn backwards!). But the actual regulation
compares the votlage on a zener doide/normal diode circuit (applied to
the base of Q4) and the 5V line (applied to the emitter). So in fact the
5V line is the one that's actually monitored.
Does anybody have the schematic for these PSUs?
There is a schematic on page 93 of the 'Apple ][ Reference Manual' that I
have in front of me. I can't find any edition number in said manual. This
is a schematic for a 110V-input only version, the 240V version is
presumably different, but may not be very different (different
transformer turns ration, but it might be the same circuitry).
I have never had to repair an Apple ][ PSU, so I have no idea if this
schematic is even close the real thing. I have found some PSU schematics
is technical manuals to be total works of fiction, though (the one in the
TRS-80 Model 3 techncial manual is hilarious!). So you might want to
check it carefully agianst the actual PCB.
-tony
5:51 p.m.
New subject: Apple II Plus power supply strangeness
Tony Duell wrote:
There's nothing inherently bad about putting a crowbar circuit on a 12V
supply, but in a microcomputer, the 5V rail is the 'important one' in
that if it goes high it wipes out just about every chip in the machine
whereas the 12V rail is used by the RAM and not a lot else. So it makes a
lot of sense to sense the 5V rail for any protection circuits (like the
crowbar).
Having the crowbar short out the 12V rail (rather than the 5V one) is
quite common in that the former can supply a lower current so it's easier
to short out, and shorting any output will shut down a SMPSU.
This PSU seems to have a crowbar circuit (SCR
Q5, zener CR20, etc), but
amazingly it seems to be connected to the 12V output. This is, IMHO,
ridiculous.
I have a few ideas as to why it could be considered a bad thing, but
I'd be interested to hear more details! When a PSU output sits at about 1V, I often
suspect that a
crowbar is triggereing, which will shut the supply down, thus enabling
the crowbar to turn off, the cycle then repeats. So what you see is an
average of the 'too high' and 'shorted' output voltages.
OK - I'll check the outputs with the oscilloscope when it's in that
mode, and see if I can see a waveform that looks like that. If the output capacitors have high ESR (a likely
problem due to old age),
there will be spikes on the output, sometimes around twice the normal
I've grabbed new replacements for all the capacitors, apart from the big
high-voltage input-side ones. One of the output capacitors has shrunk
its heat-shrink wrapping quite considerably, so I'm guessing that one
has been running quite hot. Might as well replace them all though - the
replacements only cost me NZ$10 (something like 3 pounds, maybe US$5, at
a guess) so it's hardly breaking the bank. 
17 May
17 May
6:16 a.m.
On 16 May 2009 at 22:26, Josh Dersch wrote:
It's not battery corrosion -- the board is
literally rusted, all over
:). The battery's nasty too, but that's only a small part of what's
wrong with it. I suppose I can soak it in something, maybe scrub it
with a toothbrush and see if that helps at all, but it's pretty bad.
If the board is indeed toast, you've got nothing to lose by sticking
it in the dishwasher to see how much of the crud comes off...
--Chuck
9:55 p.m.
Chuck Guzis wrote:
On 16 May 2009 at 22:26, Josh Dersch wrote:
I don't have a dishwasher :), but I carefully scrubbed it w/soap & water
& a toothbrush (and a bit of WD-40 to help loosen the corrosion). It
doesn't look as terrible now.
I put a good PRAM battery in, and cleaned off the edge connectors.
Unfortunately I get nothing when I power the system on. (It's a
two-step process -- there's a main switch on the back, but the power key
on the keyboard is what tells the system to power on.) Without the
motherboard installed, the fan kicks in and the hard drive powers up, so
I know the power supply is working (voltages seem to be fine.)
The only diagnostic ref I can find is a really really basic
board-swapping checklist. Any suggestions on what to check that is
preventing the machine from powering on?
Josh
It's not battery corrosion -- the board is
literally rusted, all over
:). The battery's nasty too, but that's only a small part of what's
wrong with it. I suppose I can soak it in something, maybe scrub it
with a toothbrush and see if that helps at all, but it's pretty bad.
If the board is indeed toast, you've got nothing to lose by sticking
it in the dishwasher to see how much of the crud comes off...
--Chuck
25 May
25 May
8:26 p.m.
2009/5/17 Josh Dersch <derschjo at mail.msu.edu>:
I don't have a dishwasher :), but I carefully scrubbed it w/soap & water & a
toothbrush (and a bit of WD-40 to help loosen the corrosion). ?It doesn't
look as terrible now.
I put a good PRAM battery in, and cleaned off the edge connectors.
?Unfortunately I get nothing when I power the system on. ?(It's a two-step
process -- there's a main switch on the back, but the power key on the
keyboard is what tells the system to power on.) ?Without the motherboard
installed, the fan kicks in and the hard drive powers up, so I know the
power supply is working (voltages seem to be fine.)
The only diagnostic ref I can find is a really really basic board-swapping
checklist. ?Any suggestions on what to check that is preventing the machine
from powering on?
If you decide to go that route, I think I have a Performa 6200 in the
garage somewhere... You could have the motherboard out of that, if you
wish. Free for the postage from the UK.
--
Liam Proven ? Profile: http://www.linkedin.com/in/liamproven
Email: lproven at cix.co.uk ? GMail/GoogleTalk/Orkut: lproven at gmail.com
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884 ? Fax: + 44 870-9151419
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MSN: lproven at hotmail.com ? ICQ: 73187508
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14 comments
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participants (9)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
derschjo＠mail.msu.edu -
doug＠stillhq.com -
halarewich＠gmail.com -
lproven＠gmail.com -
mike＠fenz.net -
mikelee＠tdh.com -
spectre＠floodgap.com