Digest for sci.electronics.repair@googlegroups.com - 7 updates in 3 topics

8:40 AM Penedão
Jeff Liebermann <jeffl@cruzio.com>: Jan 18 03:22PM -0800


>No, I'm trying to get away from having to use the battery. Something
>like a crank generator. The original Bendix model from the 50's had
>such a generator built in. It is 1.5VDC, yes and a single D cell.
 
If a hand clank generator is acceptable, then a hand crank cell phone
charger should be a good starting point. Plenty to choose from:
<https://www.ebay.com/sch/i.html?_nkw=hand+crank+dynamo+charger>
These will deliver 5.0VDC at about 0.5A. To use it in place of a
battery, you need some way to reduce the voltage to 1.5VDC. This is
called a "buck inverter" (as opposed to a "boost inverter"). These
should work:
<https://www.ebay.com/itm/122361481012>
<https://www.ebay.com/itm/175088753307>
<https://www.ebay.com/itm/401752426156>
To avoid having to simultaneously crank the generator while taking a
reading, I suggest you add a large value capacitor to the 5V input to
retain some charge while the generator is idle. I'm not sure of a
good value but something like a 3300uF 16V electrolytic capacitor
should be adequate. If it doesn't run the dosimeter reader long
enough, increase the capacitance or add some additional capacitors in
parallel.
 
I have set of 4 dosimeters and a CD V-750 reader. I made the mistake
of storing them with D size alkaline cells installed. The alkaline
cells all leaked and did quite a bit of damage. Anything you can do
to eliminate alkaline cells is probably a good idea. For the matching
CD-V500 Geiger counter, I simply installed a 14500 LiIon cell (with a
1N4007 diode in series to drop the voltage slightly) in place of the
two D cells in series and a AA to D size adapter.
<https://www.ebay.com/itm/362743539090>
For charging, I installed a charging connector in the case and use an
external charger.
 
Doing something similar for the dosimeter reader is more difficult
because of the lack of LSD (low self discharge) 1.5V cells. I'll
probably need to build a LiIon 7.4v (two cells) to 1.5V buck inverter.
Currently, I'm using a single Lithium cell:
<https://www.amazon.com/Energizer-Ultimate-Lithium-AA-Batteries/dp/B008OII4TY>
and a AA to D size adapter. It's been stored in the reader for about
1.5 years so far. No leaks and no loss of open circuit cell voltage.
 
One more hint. If you're really preparing for a full blown nuclear
disaster, make sure that your equipment can operate in very high
levels of radiation. Most equipment does not do well, will overload
easily, and produce either no reading or a useless reading.
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Chris Jones <lugnut808@spam.yahoo.com>: Jan 19 10:29AM +1100

On 19/01/2022 00:54, Juan S wrote:
> cost next to nothing to try implementing.  I don't really trust that
> batteries would be all that reliable after a crisis, which was why I was
> looking for a non-powered way to allow the 1.5V chargers to still work.
 
Thanks, fair enough.
 
I think you could rely on some Eneloop cells if you swap them for a
freshly charged one every year or two. Check that the voltage is
sufficient if the device was designed for 1.5V. Alkalikes would also do
if you could find good ones, but ones made in the last few years seem to
leak.
danny burstein <dannyb@panix.com>: Jan 18 11:29PM

In <anfeugpj7a2pdsg1m2tr3kp333kb04p6gc@4ax.com> Jeff Liebermann <jeffl@cruzio.com> writes:
 
[snip]
 
>disaster, make sure that your equipment can operate in very high
>levels of radiation. Most equipment does not do well, will overload
>easily, and produce either no reading or a useless reading.
 
People, too...
 
 
 
--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]
dplatt@coop.radagast.org (Dave Platt): Jan 18 05:19PM -0800

In article <anfeugpj7a2pdsg1m2tr3kp333kb04p6gc@4ax.com>,
>disaster, make sure that your equipment can operate in very high
>levels of radiation. Most equipment does not do well, will overload
>easily, and produce either no reading or a useless reading.
 
As I understand it, that's the reason that most of the radiation
survey meters in the old Civil Defense kits were ionization-chamber
types. They cover ranges of radiation which are actually harmful or
lethal to humans in a relatively short amount of time (minutes to
weeks). They're "no, you really don't want to be here, get the hell
away" devices, just like the dosimeters.
 
They don't respond well to low levels of radiation (background, NORM,
uranium glass, Fiesta ware, etc.).
 
Their biggest disadvantage is that they operate at such high
impedances (to measure leakage in the ionization chamber) that they're
very sensitive to moisture. As I recall, they're supposed to be
"baked" periodically to make sure they're dry, and then stored sealed
in plastic with a dessicant pack.
 
The old Civil Defense kits tended to come with a bunch of these
ionization meters, some dosimeters and chargers for them, and one
Geiger counter. The Geiger was intended more as a training device
than as an actual "when the bombs drop" tool, due to the problem
you mention... in an actual fallout zone, Geiger counters and
scintillation detectors will probably saturate and read low or
zero.
Jeff Liebermann <jeffl@cruzio.com>: Jan 18 03:34PM -0800

On Sun, 16 Jan 2022 16:44:36 -0800, David Farber
>the hard drive. The screwdrivers I have do not mach the shape or size of
>the bottom panel case screws. I believe the screws are pentalobe type.
>Does anyone know the exact size screwdriver that will fit these screws?
 
As you mentioned, the SSD and memory chips are all soldered to the
motherboard. No user serviceable parts inside. However, if feel
inspired to fix it, there are numerous teardown guides on iFixit.com.
Unfortunately, I couldn't find much for your specific MacBook:
<https://www.ifixit.com/Search?query=Macbook%20Pro%20A1989>
 
You might want to invest in a pentalobe screwdriver set:
<https://www.ebay.com/sch/i.html?_nkw=pentalobe+screwdriver+set>
or something that covers most of the weird fasteners that Apple uses
to keep you out of your equipment:
<https://www.ebay.com/itm/165232777917>
 
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Clifford Heath <no.spam@please.net>: Jan 19 11:27AM +1100

On 17/1/22 4:12 pm, whit3rd wrote:
> I'd not recommend trying non-fitting drivers, those screws are stainless and
> generally soft enough that a steel driver can hurt them.
 
 
You do well to recommend that, but in fact, two of the opposing lobes
are only 18 degrees away from being opposite, and the vertical sides and
depth of the lobes form an effective slot for a right-sized screwdriver.
There is very little risk of damaging the screw, as it turns out. The
flat screwdriver is considerably more secure than it would be in a
normal screw slot. Not as strong as a pentalobe, but quite adequate.
three_jeeps <jjhudak@gmail.com>: Jan 18 09:37AM -0800


> Can anyone tell me how models PCG-71312L and PCG-71312M differ?
> Same keyboard and caddy in the two?
 
> Thx, ... P.
 
This vendor claims the keyboards are the same:
https://www.ebay.com/itm/112044239367
Googling seems to confirm this but you should double check.
look for kbd for PCG-71312L, then look for keyboard for PCG-71312M. Check if the p/n for the kbds match.
 
No info about the caddy.
Good luck
J
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