8 Oct
2011
8 Oct
'11
7:30 a.m.
On Wed, Oct 5, 2011 at 5:08 PM, Nigel Williams
<nigel.d.williams at gmail.com> wrote:
On Wed, Oct 5, 2011 at 4:46 PM, Geoffrey Reed
<geoffr at zipcon.net> wrote:
As no one jumped in regarding my query, I thought I would venture out
along and try the tapping-along-the-seam technique previously
described and see if I could break into the dead Apple //c power
brick.
The tapping technique worked very nicely, although I had to apply
leverage with a screwdriver hammered into the seam to really crack the
two halves apart.
The scene of desolation inside revealed why it is dead-dead-dead, see
pictures here:
https://picasaweb.google.com/118247290269860741639/AppleCPowerSupplyBrickFa…
The smell is interesting too, it was nicely bottled up inside the
sealed PSU until I opened it...
Some of them were able to be opened, there were
hidden screws in the bottom
of some, ?there were also some that were 2 piece plastic heat-fused? Or
glued together.
Does anyone know if the technique of tapping along the seam will work
with the Apple //c brick power supply? which to me shows no sign of
hidden screws and looks to me "almost" seamless. 
9 Oct
9 Oct
4:56 a.m.
Quoting Nigel Williams <nigel.d.williams at gmail.com>
As no one jumped in regarding my query, I thought I would venture out
along and try the tapping-along-the-seam technique previously
described and see if I could break into the dead Apple //c power
brick.
The tapping technique worked very nicely, although I had to apply
leverage with a screwdriver hammered into the seam to really crack the
two halves apart.
The scene of desolation inside revealed why it is dead-dead-dead, see
pictures here:
https://picasaweb.google.com/118247290269860741639/AppleCPowerSupplyBrickFa…
The smell is interesting too, it was nicely bottled up inside the
sealed PSU until I opened it...
looks like all 4 diodes are blown in half or burned in half from what i could see.
5:28 a.m.
On 8 Oct 2011 at 20:56, Geoff Reed wrote:
looks like all 4 diodes are blown in half or burned in
half from what
i could see.
Ah, the smoky fragrance of burned transformer varnish!
And--my main gripe with these things--the capacitor is probably
cooked by all of the heat. Why do they even bother to put
electrolytic capacitors in a sealed linear supply 'wart?
I know--because it's cheap.
Does the transformer have a thermal overload cutout? These things
look like tiny capacitors or resistors and are designed to blow
(permanently) if the temperature exceeds a certain point. They're
required by most electrical codes in portable small appliances, such
as hair blow-dryers.
--Chuck
6:14 a.m.
On Sun, Oct 9, 2011 at 3:28 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 8 Oct 2011 at 20:56, Geoff Reed wrote:
> looks like all 4 diodes are blown in half or burned in half from what
> i could see.
the fault vaporized the solder so the diode remains are wobbling
about, a sharp tap and they would be loose inside the case. I wonder
if the design relies on the transformer to seal off the mains voltage
side? as it is a very snug fit.
Does the transformer have a thermal overload cutout?
?These things
look like tiny capacitors or resistors and are designed to blow
(permanently) if the temperature exceeds a certain point. ?They're
required by most electrical codes in portable small appliances, such
as hair blow-dryers.
I uploaded a couple more pictures, one shows the track lifted on the
underside of the PCB. Another shows the X2 across the mains but I
don't see any other components which might provide the thermal cutout.
The transformer itself appears to my untrained eyes to look ok, if it
has been severely stressed (damaged) should I expect to see any
visible sign?
7:51 p.m.
On 2011 Oct 8, at 10:14 PM, Nigel Williams wrote:
On Sun, Oct 9, 2011 at 3:28 PM, Chuck Guzis <cclist
at sydex.com> wrote:
A thermal cutout may be buried under that yellow wrap (it may be that
bulge where the wire goes under the wrap) where it is held close to the
winding for heat sensing. You could test for continuity of the primary
with an ohmmeter.
I would expect the transformer is likely OK, you could remove the
diodes, clean out burned traces to make sure there are no shorts, then
plug it in and check for sensible AC voltages out of the
secondary(ies), and that the transformer doesn't heat up inordinately
with no load.
On 8 Oct 2011 at 20:56, Geoff Reed wrote:
> looks like all 4 diodes are blown in half or burned in half from what
> i could see.
the fault vaporized the solder so the diode remains are wobbling
about, a sharp tap and they would be loose inside the case. I wonder
if the design relies on the transformer to seal off the mains voltage
side? as it is a very snug fit.
Does the transformer have a thermal overload
cutout? ?These things
look like tiny capacitors or resistors and are designed to blow
(permanently) if the temperature exceeds a certain point. ?They're
required by most electrical codes in portable small appliances, such
as hair blow-dryers.
I uploaded a couple more pictures, one shows the track lifted on the
underside of the PCB. Another shows the X2 across the mains but I
don't see any other components which might provide the thermal cutout.
The transformer itself appears to my untrained eyes to look ok, if it
has been severely stressed (damaged) should I expect to see any
visible sign? 
9:01 p.m.
Quoting Nigel Williams <nigel.d.williams at gmail.com>
Now that I've maanged to view the pictures, my comments...
It's clearly a linear suppl. The 4 diodes and capacitor provide a DC
output (unregualted). Is that the only output, or are there AC outputs too?
What I do do first is desodler the transformer secondary connections from
the PCB and put the PCB aside. Check the continuity of the primary
winding (between the live and neutral pins of the mains input plug) and
the secondary (or -ies). If any are open, the transformer needs a rewind.
Actually, if the primary is open, there may be a thermal fuse inside the
trnasofmer that has failed, protectign the rest of it. You might be able
to find and replace that without rewiding the whole thing.
If you have a 'megger', do an insualtion test on the transfomer --
between each widing and the core and betwee the primaray and each
secodnary winding.
Then, with The PCB still removed, connect mains with a ligbt bulb
(low-ish wattage) in series. It must be a real filament bulb, of course.
The blub should remain dark. If it glows, you'ge got shorted turns,
probably due to burnt insulation. again rewind time...
If the transofmer is OK, then it's probably worth replacing the 4 diodes
and the capacitor (the latter may be OK, but I woudn't trust it! That
should get it going again.
-tony
As no one jumped in regarding my query, I thought I would venture out
along and try the tapping-along-the-seam technique previously
described and see if I could break into the dead Apple //c power
brick.
The tapping technique worked very nicely, although I had to apply
leverage with a screwdriver hammered into the seam to really crack the
two halves apart.
The scene of desolation inside revealed why it is dead-dead-dead, see
pictures here:
https://picasaweb.google.com/118247290269860741639/AppleCPowerSupplyBrickFa…
The smell is interesting too, it was nicely bottled up inside the
sealed PSU until I opened it...
looks like all 4 diodes are blown in half or burned in half from what
i could see.
4607
days inactive
4608
days old
5 comments
5 participants
participants (5)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
geoffr＠zipcon.net -
hilpert＠cs.ubc.ca -
nigel.d.williams＠gmail.com