For each of my expensive tubes (b7971, R|z568m) I measure and plot the I-V
characteristics. There aren't any serial numbers on b7971's so I just write
one on the backside.
If the tube fails later on, I check the I-V characteristics to see if
anything changes; so far only 1 b7971 has failed
I'm seeing long delays from the Czech Republic as wellordered 2 tubes
from Dalibor, which were quickly shipped, but there has been no update
since April 27, with status of 'sent to destination country'. Either it's
waiting for a flight (most likely), or it's landed in the US waiting to be
The voltage tripler as shown requires symmetric positive and negative
cycles. The flyback topology you are using is primarily unipolar, so it
wont produce the symmetric positive and negative cycles like a line-powered
transformer does.
If you are going to use a flyback topology with a voltage
Looks like you have a second board behind, with colon partially visible.
I hope you bought your tubes awhile back; the recent b7971 prices are crazy.
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I have an 8-tube clock with b7971's and whenever I find the time... I will
add a software routine that calculates which segments will change, and
instead of changing them all at-once, they will be split into a few groups
that change every 50-100msec. I think it would be too distractive for
Ideally, you want a totem-pole driver for the SN74568 because it will
shunt-away some of the leakage current that would otherwise get amplified.
You've got me stumped on the 3.3V vs 5V observation. The only thing I can
think of is the 3.3V driver has stronger pulldown than the 5V driver (need
[image: ScreenHunter_26 Apr. 29 11.35.jpg]
I use a simple NMOS current-limiter in my HV supply. Basically, there is a
resistor on the source lead, and the voltage-drop across that resistor
provides negative feedback. To set the current-limit, I have a 10-turn
potentiometer to set the gate
And it finally sold for 255 USD. I hope the winner is in this forum and
makes something with it.
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I suspect that leakage current is causing the Darlington driver (2-stage
high current-gain amplifier) to turn on. With a base resistor (see
datasheet), any leakage current into the base can still get amplified,
because some of it will leak into the Darlington-pair and get amplified. A
scope
The SP-151 is durable; I built a wristwatch a few years ago with the same
unit my father got as a sample back in 1974. In fact, the prototype on my
workbench is still running after 5 years on the *same* charge I put on the
Li-ion battery (yeah, the battery drives the display and the RTC).
Nick - How much business have you done on AliExpress ? I've only bought 1
item (box of 1000 green NE-2 bulbs), and the sale was fine, but I've heard
concerns some sellers aren't vetted like they are on Ebay.
There is a lot of really neat industrial product available, and I'd like to
purchase
As much as I would love to have my own curve-tracer, I have to be
practical. The transistors I select have SPICE models, so I simulate
everything in detail.
Nixie tubes, especially the rare or expensive ones like b7071 and R|Z568 ,
I generate I-V curves by hand for each segment/cathode. A
When I was in high school, I got to use a Tek 575 curve tracer. Perfect
instrument to nail-down any differences between these devices.
Every now and then, I take a look on Ebay and ask myself if I should buy
one. Yikes...I just took a peek and there are several available.
Fortunately I just
It's the leakage (Icbo) that is 1000x greater in the MJE device, not the
current gain. There are many factors affecting leakage and current gain:
- Some are environmental (temperature, reverse-voltage, operating
current)
- Some are device construction (physical dimensions of base width
Much of the additional leakage current is caused by the higher DC gain of
the MJE device; the datasheet says gain peaks around 240.
Basically, the reverse-leakage current from the collector-base junction
gets amplified by the DC gain (beta), to produce the overall leakage (Icbo)
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I'm absolutely certain the MJE die is physically larger. For one thing, it
must conduct more thermal energy to the case.
Another tip-off is the difference in DC current-gain, and that in-turn
accounts for part of the 1000x difference in leakage current.
I believe leakage current is directly
There are thermal considerations; the MJE340 is designed to be used on a
heat sink and is rated for 20W, vs 1.5W for the MPSA42.
Also, there are some differences in the safe operating area curves; the
MJE340 can tolerate a bit more current at any given voltage.
MJE device also has a lower Vce
Terry - How did bombarding go ? That is the main reason why I never took up
neon design; it's pretty dangerous.
I've also wondered about how much vacuum equipment is really necessary;
some books suggest you need to get well below 50 microns to get a good
tube. That's way outside my budget and
Not my item / no affiliation:
https://www.ebay.com/itm/EXPERIMENTAL-NIXIE-TUBE-DEVELOPMENT-SAMPLE-PANDICON-RARE-UNIQUE-9-segment/223985955147?hash=item34269a714b:g:RKwAAOSwKk5eoG8n
9-segment displays are uncommon, and the nice thing about them is you can
make fairly decent-looking words with
The 4mA minimum load is livable; even at 300V it's only 1.2 watts. It's
probably required for safety reasons so that you dont have an open
unregulated output. In fact, a lot of switchmode supplies require a minimum
load, otherwise the output goes to zero volts.
Please be VERY careful with this
Very interesting.I assumed that typical flames didn't radiate anything
significant in that lower wavelength region..
Do these detectors have a gas that ionizes when UV is present ? That would
make the most sense since UV is higher energy than visible light.
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Are they thermally-activated, or is it something ingenious, like
visible/infrared detection ?
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Let's suppose the meter WAS connected properly..then what ?
Since this has a dc-dc converter, it's possible the output was pulsating,
rather than smooth DC. In which case the meter might be attempting to
measure peak or RMS current.
In that case, the higher-than-expected reading might
Where, exactly, did you measure the current ? Best if you can post the
exact schematic and where your meter was located.
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Level-shifters, such as the MC14504, are cheap insurance to guarantee
proper logic levels at the HV drivers. You can use a resistor-divider
at the and of the serial chain to read the data back into your controller
so that you can verify the integrity of the chain..
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Ping me when you start energizing them. I've already done some basic
experiments and there are some learnings you will want to leverage.
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What makes the axe-man go on a rampage ?
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Michail - Have you decided when you are going to start the design work ?
I will be using the displays in groups of 2, with one of them turned
upside-down.
This allows you to use the decimal points for a colon, and it reduces the
wiring clutter because the pins face eachother. I was thinking of
I'm very impressed at the price (99 USD). I bought 7 of these tubes awhile
back for a future project, and I know it's going to cost me a lot more to
build it, not to mention the amount of time to develop it.
I'm skeptical about the power consumption (5V@1 amp = 5watts). The
filaments alone
The one-and-only "antenna" version of the b7971 I had in my 8-tube clock
failed as shorted segments after 2 years of usage. Not sure if others have
seen reliability issues with a particular tube style, but that's my
experience. I only use direct-drive, and the clock is well-protected from
If someone could post good-quality pictures of the PCB (both sides), that
would satisfy my curiosity .
I definitely remember the Poly-Pak ads, and at the time I was not
electronically-adept enough to design the drive electronics so I bought a
bunch of LED displays instead.
I also had a 6-tube
I've bought similar bulbs, with leads. Several years ago I bought a box of
1000 green "NE-2" from China, and sold a few batches to neo-nixie members.
It's hard to tell what the internal gas is, but when it ionizes it also
causes the phosphor coating of the bulb's interior to glow. The nice
How functional is it ? If it's totally dead it might be worth checking the
power supply.
I would suspect some keys no longer work due to contamination after almost
50 years.
Russian VFD's are still cheap and plentiful so the scrap-value of this
calculator seems low to me.
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I use a manual suction device to get most of the solder out, flex the lead
with soldering tip to make sure it's no longer attached to the via, then
cleanup with braid after the part is removed. Lastly, clean-of flux with a
swab moistened with appropriate cleaner.
Often, it's easier to snip the
That topology wont work for getting HV for driving a nixie tube. The
original design uses an inductor and operates as a boost-converter to
produce a higher output voltage, generally around 5V, from the input.
When you replace the inductor with a transformer, you are taking energy out
of the
Opportunity is knocking on Dalibor's door for a "Rb|7971"
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There were two b7971's available last night on Ebay at 150USD each, used
and *untested*. They are already gone.
This is crazy.
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Are you OK soldering them ? As long as you have a good-quality PCB
manufacturer, the PCB will tolerate rework (install-remove-install).
I had to deal with that with my watch; soldered-down an SP-151, then found
I had to unsolder, remove, and re-install. Wasn't too bad.
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Can you measure the segment current ? For a given current, the brightness
should be similar for tubes in the same condition. If not, there is a
problem with manufacturing consistency. As VFDs age, they produce less
luminous output. Some will develop visible dark bands nearest the
filament(s),
Can you provide the manufacturer part numbers for the header-sockets and
pins you are using to mount the small PCB's to the motherboard ? I have not
been able to hunt those down on Digikey's site and I'd like to use them for
a future project.
Very nice job with the overall construction. What
Just sent directly to you; I've been very busy dealing with a knee injury
and all of the work/life changes due to COVID-19. Working from home makes
everything more difficult and less efficient. Once you have the gEDA tools
installed I can assist with using the files.
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I was thinking he would stay with gas-discharge, but allow custom tooling
from a .gif file, etc . VFD is a very different beast.
I've seen phosphor-coated novelty bulbs that give other colors, but they
have short lifetimes (500 hours typically)
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I made a "lucky: offer of 7.77 USD, and Ebay pop-up told me to make an
offer above 5832 USD..
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Not quite an "upside-down airplane" postage stamp, but.Most likely an
engineering sample.
Not my listing or anyone I know.
https://www.ebay.com/itm/Lucky-nixie-tube-unique-artefact-77-plasma-indicator/114149048472?hash=item1a93d04098:g:8WUAAOSwS3JebOxT
[image: ScreenHunter_25
I will dig them off my server this weekend and email them directly to you.
On Thursday, March 12, 2020 at 2:01:33 PM UTC-7, ZethieTail wrote:
>
> wheres the files tho? im still new to the group
>
>
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You would tie the decimal point to a positive supply (like the other
segments) thru a larger resistor. I would start with a resistor value 10x
higher than the series resistor on the segments.
To prevent wearout, use the lowest current that gives acceptable
illumination.
I didn't see anything
You would need hundreds of 22V10's to do the watch; If the HV supply was
redesigned, you could use a microcontroller, though I doubt you would have
the power-savings I have.
I'll give you the SP-151 footprint & symbol files; when you have those
working in gEDA tools I can provide the
Not sure if you meant my wristwatch, or Westdave's clock.
I have design files for gEDA PCB, etc, but I dont recommend this design to
anyone for a wristwatch. My HV power supply overheats after 15-20 seconds
of continuous usage (transformer saturation).
The original watch shown in my photo
I have an informal "museum" on my desk at work; all tubes are functionally
dead (gas leak), but they otherwise satisfy everyone's curiosity.
Original plan was to use a display case, but people like to hold them, etc.
Everything else is archived in tube boxes, and kept in a metal ammo box.
The more I think about this, the more I think I will just use a 75 USD LCD
touchscreen for the RasPi, and define my own keyboard.
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Is someone interested in bringing-up 1 or 2 calculators with the original
system, and selling-off the other 2-3 calculator terminals ?
That way, a good chunk of the original machine is preserved. I do feel bad
destroying it.
I'm mostly interested in the keyboard because it will cost me about
orbuild a clock so you can *enjoy* them. What good is a bunch of
50+ year old tubes sitting in the box ?
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I will say this much: The RasPi is such a complete, convenient, and
low-cost (10 USD) platform that gives you easy hardware control thru
C-language, that I will not consider any other platform for many years to
come.
Bringing in the keyboard signals to software is simple, and controlling
I would be willing to go in for 1/3 or 1/4 share for 1 of the desktop units
and replace the brains with a RasPi.
Hopefully there would be enough room in the desktop unit case for a PC
board, and use an external laptop power supply.
I have no interest or desire trying to resurrect the control
What is contained in the control unit vs the desktop unit ? Is this similar
to a compute-server and remote terminals ?
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Let's face it.we're all a bunch of nixe-holics, nixie-junkies,
neon-tweakers, or whatever you want to call this addiction.
I agree the price is high, but someone out there is going to buy it and
make something they will be proud of, so that's all that really matters. I
just spent more than
I would start with a few ideal scenarios to understand your total power.
For example, if you use 180V most of the time, and have a short "boost"
when bulbs need to turn on, your power will be minimized.
But with all segments on, that works out to 180*26*4*0.013 = 243 watts to
display , and
You probably just want a HV supply, about 250 VDC, and a fuse instead of a
constant-current supply.
I think IN-28's are rated at 13mA, so you could arrange them in groups of
16 with a 1/4 amp fast-blo fuse to protect each group.
If power consumption is a concern, you can get clever and step-up
Essentially, yes. But be aware of the open-circuit output voltage; the
supply will attempt to pump-out the amount of requested current, and in
order to do so, it will increase it's output voltage until the desired
current is obtained.
Just make sure that *you* are not the load. For example, if
A-101s are phenolic-base, and very reliable. Mine has been running 24/7 for
7 years now, with no signs of degradation.
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Fundamentally, it should work, but be aware you are now pulsing the
displays. Some folks in this group have reported audible noise from
multiplexing. Some panaplex displays require multiplexing by the nature of
their pinout (common cathodes, separate anodes) so that would be a moot
issue.
These use current-sensing transformers intended for line-frequency loads,
and most-likely passive (RLC) loads. So, not for DC.
I've seen DC volt and ammeters, but they will require a separate power
supply.
The nice thing about the AC-line monitors is they are self-powered, and
seem to run down
I've started putting these in all of the line-powered equipment I make. So
cheap and easy to use. They even have versions that fit into a knockout for
1/2" conduit fittings.
As LCDs continue to get cheaper, someone is bound to make a nixie (or
perhaps NIMO) font.
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There's some hinting of multiple reflections when you look at the '2' very
carefully, which happens with edge-lit, but it looks so incredibly-nixie
because they did an outstanding job.
The creator said he used acrylic for the edge-lit numerals; I was expecting
high-quality optical glass.
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I'll take a dozen NL7037..
I do remember getting one of these catalogs from Radio Shack back in the
70's; pages and pages really neat stuff.
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Yuriy - Someday you need to write a book about your adventures as a
tube-hunter.
Finding 3600 tubes is amazing; congratulations !
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Definitely a must-have if you want to measure your time-dilation on a long
airplane flight, or perhaps when climbing a very tall mountain ?
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It's really a matter of what you want for a reference. A
Rubidium/Cesium/whatever reference will give you a very stable 10Mhz timing
reference, but it *wont* give you the official time-of-day. Every so often,
there are corrections to official world time and if you're using a stable
timing
Neglecting switching characteristics for a moment, the only 2 parameters
for a free-wheeling diode are (1) it must safely handle the peak inductor
current, and (2) the reverse-breakdown voltage must be greater than the
supply voltage. In operation, it acts as a regular diode to provide a path
Oy vey, Rube Goldberg would be proud.
The zener diode should be around 12V; it needs to less than the
maximum-allowed Vgs for the MOSFET so that the MOSFET is protected. If the
zener diode is less than 12V, it will consume a few mA when the solenoid is
energized, but that's harmless.
Now,
OK, if the input is mechanical, and basically shorts-to-GND for turnin,
then you're OK because the resistors you have will act as a pullup, and
shut off the MOSFET.
Next, we need to look very carefully at the circuit layout, because there
are ways the free-wheeling diode could en-up not
If there was any kind of electrical surge/transient, it's possible the
gate-source was damaged, though we'll never know for sure. MOSFETs can fail
in the shorted (on) state, and that would also fry the coil. Automotive
electrical environments are not well-behaved, and prone to transients when
About 3 years ago I gave away my extra boards (only charged for shipping)
to 3 members of this forum; I just sent out a ping to see if anyone has
built theirs yet. The gerbers and docs are posted to the private group (
https://groups.google.com/forum/?hl=en#!forum/b7971-driver-board-user-group
Our bedroom clock has 8 tubes (b7971), and is PIR activated. Needless to
say, it's very bright when on. I set the timeout to 100 seconds, and I dont
ever recall being awakened by the display turning-on. A future project is
to modify the code so it reports how many times the PIR sensor was
Speaking of b7971's , I see a pair of untested 7971's on Ebay with a
starting bid of 150 USD eachyikes.
I'm glad I finished mine a few years ago.big tube, and quite versatile,
and a bit ugly.
Whoever is determined enough to acquire a batch of these, rest assured
you'll get used to the
On Monday, January 6, 2020 at 11:22:41 AM UTC-8, Pramanicin wrote:
>
> An Objet d'Art?
>
>>
>>
Absolutely, though a 6x6 could also display crude alphanumerics. The basic
idea is an FPGA to sequence each dekatron, and process commands from a main
control device, such as a RasPi. Patterns would
I'm glad to see someone actually built one; I've had a 6x6 (yep, 36
dekatrons) on my back burner for a few years now.
My base is 3D-printed; each "tile" is a 3x3 array of tubes, and I have 4
tiles.
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Odd they are priced so high; maybe a rare tube?
IN-18's are 10mm taller (40mm) and list for around 50 USD each.
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I've wondered about using small CRTs, such as the 3L01I, to emulate a NIMO
. Back-burner project for me.
LCD/OLED allows you to mimic any kind of display/font/color/language and
no worries about un-obtaianble display devices.
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Yeah, right call to scrap it.
How long are your VFD tubes lasting ?
Do you keep the filaments always-on ?
Are the phosphors always-active, or do you shut-down during certain hours,
or use a PIR sensor ?
I'm planning to make a night-clock which slowly turns-on the filament
supply after the PIR
I still have my $10 APF scientific calculator from 1976 which got me thru
high school, college, and did my taxes on it for a few years thereafter.
The VFD display is still working nicely. Not programmable.
BTW, that price ($10) is what I paid for it in 1976 at a drugstore. It
outlasted the 2
Listing mentions it was built by his grandfather. It definitely looks
"rough around the edges", but he certainly put his heart into it.
If I ever end up having grandkids, I hope they will keep my clocks alive
with the spare tubes I have rather than sell them on Ebay.
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I guess this is one of the uglier devices from the 1970's that's not worth
keeping/fixing as a clock-radio ?
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I made a wristwatch with a similar device (SP-151). Segment current is
335uA, which is right around what you mentioned.
If you are multiplexing, you may need to tweak the segment current and
timing; mine is direct-drive.
Making the PCB footprint was a challenge; I used a digital caliper and
I'm certain that dim phosphor near the filament is an unfixable wearout
mechanism caused by electrons (from the filament) bombarding the surface.
The electric field-strength is at it's highest closest to the filament.
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I just bought 3 NOS VFD tubes, still in their original Radio Shack
packaging.
I'm testing one of them, and noticed that some anodes are not glowing
fully, and in fact require a much higher voltage to get decent brightness.
I'm wondering if they have been sitting around for such a long time that
Very cool! How much current does the argon tube require ? My recollection
is that Argon radiates significantly less energy in the visible region
compared to neon.
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Reduce the resistors to increase the LED segment current. I assume you are
doing 8:1 multiplexing, so each digit is only on for 1/8 of the time
therefore you need more current.
Many years ago when I built my first computer, the HEX display that I
wire-wrapped used 10:1 multiplexing and the
L3 is before the mixer, so it's still 88-108Mhz raw VHF (FM). My best guess
is that L3 and the resistor make up a crude high-pass filter, especially if
this is an AM/FM radio, to prevent AM (and other signals) from interfering
with the mixer. I dont understand why the other side of the coil has
A close-relative of the Y2K problem that was a hot issue 20 years ago.
Now, for those of you who use software-based solutions such as the RasPi,
there is a ticking time-bomb waiting for us on January 19, 2038. On that
date, all software using 32-bit signed integers for the time will overflow.
Looks like 64x64 matrix, probably 64 anode-connections on 1 side and 64
cathode connections on the other. I would expect a lot of flicker with 64:1
multiplexing at 1Khz; that's basically 16Hz flicker-rate.
Even the 128x32 dot-matrix displays used on pinball machines have annoying
flicker in my
If you have a digital scope, here are a few things to try:
1. In your controller, add a few lines of code to wiggle a spare I/O pin
when the controller gets reset. Then use this to trigger your scope; if
noise is causing your controller to restart, your scope will catch it. I've
done this, and
There are drop-in replacements for the 'old-school' linear voltage
regulators, and they use high-frequency switching to minimize the component
sizes.
Recom Power makes several of these, and I've used them on several projects
with no problems.
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Is anything besides the transformer getting warm ? This is where a laser
thermometer is very handy.
How dirty/dusty were the PC boards ? In my garage it's possible for metal
fragments to get everywhere.
Try brushing/vacuuming/blowing w/ compressed air. I know it sounds gross,
but sniff around
As long as you have direct software control of the 3 GPIO pins (shift,
load, serial_data), it's fairly simple to write a routine to send serial
data. Just make sure that you *never* change more than 1 GPIO pin in the
same instruction, otherwise you run the risk of a logic race condition and
The Maxim part you mentioned is for VFD's, and it looks like it can run as
low as 8V. If you use it to drive the anode of your LEDs, you run the risk
of exposing the logic driving the cathodes (segments) to roughly 6 volts
(the LED has about 2V of forward bias).
If the Arduino has 5V-tolerant
Copy that. Off-the-shelf metal could easily be recycled and contain a lot
of impurities.
Once he's sold enough to invest in helium leak-detection, and moved the
tubulation away from the crimp, I will consider buying one tube to
experiment with.
Getting a uniform glow across the digits was a
I see similarities with Dalibor's manufacturing process, notably the flat
crimp for bringing-out the leads. The tubulation at the base is different,
and typical of many nixies. It appears the numerals are hand-made by
bending wire. The connecting wires glow along with the numeral. Still, very
Given my age (I'm approaching 60), I'm not taking any chances getting
shocked; one wrong zap and my heart is toasted. I usually take more
precautions than reasonable, and that's probably why I dont recall ever
being shocked working on a project. It's the everyday things (lawnmower,
fish tank)
I dont think that cap is directly exposed to the push-pull activity from
the vibrator/transformer, but there could be some second-order effects.
Note the series inductor; that raises the possibility the cap could get
exposed to reverse voltage.
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