When ICs are produced some flunks final QC test. They are not dead but
does not meet standard. Cheap meters have those flunked chips. Radio
shack sold many of those flunked stuffs for hobbyists. Problem with
those are hit and miss and unreliable. If you use one of this bastard
chips in a timing critical circuits. The result is very annoying.
They have been doing that for years. Much of the stuff from Radio Shack
seemed to be on the low end. I never did use very many of their components
unless I had to get something going in a hurry.
I guess they probably still do, but many of the computer chips were tested
and sold by price and the maximum speed they would work at. I think it was
Apple that had a memory board that took a chip with the same number, but a 1
or 2 or A or B on the end. Half the memory was bad on enough chips that
thwy were sorted as to left half or right half good , so to speak.
In the early 80's (? maybe flakey meatware) you could purchase "32K bit"
No one *made* 32Kb DRAMs -- they were 4K, 16K, 64K, etc. But, there was
enough "value" in a 32K device that vendors would sell 64K parts that
had defects confined to one half of the array (telling you which half
you could RELIABLY use).
Of course, there was nothing that prevented you from *trying* to use
the entire array! You might get lucky and discover that just *one*
cell was toast. Or, as many as 32K of them!
For a business, this was folly -- you can't engage in wishful
thinking ("Hopefully *all* of the components that we get will
have JUST ONE bad cell!"). But, as a hobbyist, you could get
a real bargain -- especially when you needed 8 of them to do
That;s why they make battery powered kit! :> My Simpson (VOM) came from
a guy who used it for field work. It was too "pretty" to pass up,
at the time. Now, it mainly collects dust as one of the smaller Fluke
DMMs has about the same footprint (and I don't have to interpolate on
an analog scale!)
We used to pick them up -- or whatever was the freebie du jour -- each
week (no purchase required) on the way to volunteer gig. You'd find
dozens of them lying around -- along with HF screwdriver "kits",
scissors, box cutters, flashlights, etc. All "disposable" (not
very good quality) but that's what you wanted -- you certainly didn't
want to bring in *good* tools and discovered someone had walked off
with them (or, simply LOST them!).
The plastic bits around the jacks for the test leads seemed to
break quite frequently. But, again, no one was really treating
these things like "investments".
It was there that I adopted the "disposable" mentality: picking up
a meter, chasing down a pair of test leads and *then* discovering it's
batteries were dead, or display cracked, or selector knob gummed up,
etc. was frustrating enough -- the possibility that you MIGHT repeat
this same exercise later that day, week, etc. made it much easier to
just pitch the flakey items in the "recycle" bin. And, stop by HF
next week for a replacement! :-/
Again, having many of them lying around, if you happened to probe
the power supply on a disk drive and see "11.2V", you could pick up
another meter and get a second opinion. If significantly different,
take the one that is misreporting and discard it.
I had a guy I worked with at one of these places who would hold
onto "partially working" things. Like, an AM/FM radio that
only receives AM. "No, that's not an AM radio. That's trash!
Look through that pile of AM/FM radios over there and see if you
can find one that receives AM *and* FM!"
Sounds like that FET volt meter I have. Uses some odd 8 volt battery . I
have a friend that has an old Triplett VOM and it uses about the same
battery, or it could be a 22 volt unit. He found one but it was about 20 or
30 dollars, so he passed on it. All it does is power the high value ohms
scale so it is not a total loss.
My triplett VTVM is real vintage. It has vacuum tube. To use it has to
be plugged in. FET is similar in characteristics to vacuum tube. Seldom
fix MOSFET guitar or bass amps for son's friends. I still modify quality
HiFi mono block tube amps to clone guitar amps and give them at cost.
Poor man's Marshall, Fender, Boogie amps. These mono blocks are going
pretty cheap at eBay. Always shipping costs more than price, LOL!
Yes, but *actual* capacity is all over the map! Like buying
a "bottle" of milk and discovering it really only holds a
quart -- even though it *looked* like it was gallon sized!
I think it depends on the device, the peak power drain and
the operating ("per use") lifetime.
E.g., our portable vacuum cleaner is good for a couple of
minutes of operation (batteries are old and don't hold a
strong charge). This is OK for us as we only use it when
we have "a few crumbs" to clean up -- and don't want to deal with
dragging out the REAL vacuum cleaner for such a small task.
A cordless soldering iron that I have is similar: uses lots of juice
but for just a few seconds at a time. Then, set it back in its
stand (which, amazingly!, is a CHARGER! :> ).
OTOH, if I'm stringing network cables on the underside of my work
benches, I will typically use something like:
sitting flat on the floor, pointing upwards to illuminate the
underside of the tables. After a while, the batteries (esp
if they are the original HF batteries) go dark. So, swap
them out (if rechargeable) with the spare set in the charger
for *next* time.
[crap! I've been meaning Harbor Freight and think I've been
saying "HD" -- instead of HF! :< Apologies to Home Despot!]
I think originally it was because the semiconductor "process"
wasn't as effective at lower voltages and power levels.
When making safety related things, change always draws attention
Atty: And why, sir, did you authorize the change from the
long standing, well proven, reliable design to this
NEW design? The design that was present in the home
of my client's LATE parents??
They are particularly handy for throwing a lot of light *up*.
Conventional flashlights don't stand on their ends, well! :>
Also has a magnetic back so you can "stick it" onto
one of the metal workbench legs if you need the light in
some other space.
And, you can store it hanging from a "teacup hook" screwed
into the underside of the workbench!
I don't think I would ever *pay* for one of them (I think
all I've ever bought from HF was utility knife blades?)
but, "for free", the price is right! :>
Our detectors battery is only back up during power failure.
Same with alarm clocks. Power failure is very rare in our
neighborhood. Longest was like 5 hours once years ago during ice
storm. This is there was one during severe thunderstorm, 20 mins.
I have one watch runs on solar and equipped with 3 radios for time
signal. Can receive and sync time in NA, EU and Asia.
That's the new trend and, AFAICT, required in new construction.
But, battery is still tested while running on AC power. For
our (dual AC/DC) units:
If any form of battery failure is detected the red LED light
will flash and the unit will “chirp” one time, followed by the
warning message “LOW BATTERY”. This cycle will occur once every
minute, and will continue for at least seven days.
Yeah, I *really* want to listen to that if it happens in the middle
of the night! (not!)
Note that the detector can be temporarily silenced for *nuisance*
alarms ("Dinner will be served at the sound of the smoke detector!")
but not for the low battery reminder (I guess they don't consider it
a NUISANCE to babble "LOW BATTERY" every minute for 10,080 consecutive
Also, the detector *claims* it will conspire with its peers to adjust
its sensitivity -- again, presumably, to minimize spurious alarms.
But, when the battery quits, it will nag you EVEN though you have
AC mains powering the unit! (OhMiGosh! What if the power fails
while the battery is low??)
We had a distribution transformer for the neighborhood catch fire
which cost us most of a day. Another time, a cable fire in a vault
(our utilities are below grade) ate up a day while new cables
I have a couple of crank-powered radios -- along withone that has a
large *mainspring* that will drive the generator mechanism for a
full 15 minutes! And, UPS's serve for short term backup power;
plug a few CFLs into a UPS and the neighbors wonder why *you*
(appear!) to have power but they *don't*! :> The batteries
in the electric wheelbarrow will keep the house "lit up"
for close to a day!
A friend is dropping off a genset for me to "rescue". This will allow
us to keep the freezer in the garage operational during outages as
well as the furnace (in the event it is a winter outage). Can't
do much for the ACbrrrr during an outage...
My generator will run the AC no problem - and a few other things at
the same time if I run it on Gasoline. On Natural Gas the AC gets
pretty close to it's limit (5500VA on natural gas or propane, 7200 on
gasolinr with 9000 peak)
On 10/3/2015 4:19 PM, email@example.com wrote:
~4.5T unit so it would be close for your genset. Note have to run the
compressor *and* the furnace blower. No idea how big the unit being
gifted to me is. And, we'd have to stagger the compressor in the
freezer with the compressor/blower in the ACbrrrr/furnace.
In any case, we can easily live without AC for short durations (days)
as many folks here don't have dual cooling. And, if it's a dry part of
the cooling season, the swamp cooler does a great job with a fair bit
The real "need" is for the freezer -- too much $$$ stored in there to
just let it thaw due to lack of power! And, trying to "cook everything
before it spoils" -- on an electric range -- would just make an
unpleasant situation that much worse! :>
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