On 7/9/25 15:11, Viesturs Lācis wrote:
pirmd., 2025. g. 7. jūl., plkst. 19:17 — lietotājs gene heskett
(<ghesk...@shentel.net>) rakstīja:
The inability to absorb the higher frequency
noise may be the reason its eating the 7i48's outputs. Your scope should
be able to show those spikes, typically needing at least 100 MHZ of
bandwidth to show them with good accuracy, probe ground leads as short
as practical.
It seems that I will have to look at this. Should I expect those
spikes at somewhat stable pattern or totally random?
Electrolytic caps should always be used at 90% of rated voltage or even
higher., a 16 volt cap used in a 3.3 volt circuit has a failure time
generally under a year. The under voltage allows the cap to "deform"
losing capacity in the process.
Thank you for this little piece of information!!! When choosing caps
for rectifiers I did choose such a voltage to have extra margin. It
just felt better. Now it turns out that it was bad and unjustified
choice.
That recommendation depends on the circuit, that was referencing a dc
blocker or rail bypass isolated in a logic circuit. For psu filters,
one normally assumes the peak voltage to be in the area of 5% over
1.41*input rms voltage, a value not always accurate for digital meters ,
so what ever your multimeter says the supply voltage from the breaker
box is, it s/b multiplied by around 1.42 to get the voltage to buy for
the filters. This should come out, for a shop here in the states as
something like 126 to 128 on the meter, times 1.42, or 181.76 volts, so
use a 200 volt cap. A 150 volt will work, about long enough to get to
your ride, but it will be heating and eventually blow up like a weak
dynamite cap. Messy. Not at all pretty.
SECRET: ESR meters vary in accuracy, but there are $22 kits on fleabay
or amazon which can actually work for stuff like this but you need to
isolate one lead of the cap or both to isolate it from the other parts
around it. Top of the line is just under $200, made by a guy in Omaha,
Nebraska, USA, called a Capacitor Wizard. Has all gold plated probes and
does its checking with only a 50 millivolt signal, too low to be
confused by the conduction of a nearby transistor or even a Schotkey
diode might have, so you can measure all the caps on a board full of
digital stuff, 100% in-circuit.
I will rephrase my original question - can anyone suggest ANY place
where I can get a 8i20 drive? Today I discovered that
store.mesanet.com is also out of stock on this item. Even if I fix
that Yaskawa for now, I would like to have one spare 8i20 under my
pillow.
Peter I expect can repair failed 8i20's, have you asked him? I haven't a
clue how much of a headache customs might be where you are though.
Viesturs
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Cheers, Gene Heskett, CET.
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soap, ballot, jury, and ammo. Please use in that order."
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