Building a Dim Bulb Tester
A note before getting started: know what you’re getting into before messing with mains voltages. Do not follow this article if you do not have experience with mains voltages, and even if you do, don’t blame me if you get zapped.
As time goes on, electronic test equipment has become very advanced, cheap, and available for enthusiasts and professionals alike. This equipment, like oscilloscopes, logic analyzers, function generators, and multimeters, oh my, are all very powerful tools to use. Though, in the day in age of microprocessors, FPGAs, etc. even lower cost equipment is remarkably complex. This complexity is often lost on the user, as they’re using this equipment to design or repair something of equal or greater complexity. However, complexity is not a prerequisite for a powerful piece of test equipment, and that is where the dim bulb tester shines, or doesn’t, depending on what you’re working on.
The dim bulb tester is simple both to understand and to build. The basis of the circuit is to place an incandescent light bulb in series with a problematic piece of equipment; the incandescent bulb being a similar wattage to that of which the piece of equipment draws. Since this bulb is in series with the piece of equipment being tested, if the bulb begins to glow while the piece of equipment, say an audio amplifier, is not under load, this would be indicative of a short, as the equipment is drawing enough current to illuminate the bulb. A popular use of the dim bulb tester is when powering up old analog radios or stereos for the first time, helping ensure the magic smoke is kept in and indicating potential issues. I specifically am building this dim bulb tester to help me repair a Marantz 1060 audio amplifier I purchased broken from an antique radio show.
The parts and tools required for this project are very minimal and inexpensive. I spent approximately $10 on all the parts I needed, and only used very basic hand tools to assemble. I did not need to purchase the appliance cord because I am a packrat that insists on saving cords from broken things. I also did not need to purchase the Romex wiring as a friend is remodeling his kitchen and gave me a length of some of the old wiring (thanks Josh).
The parts list is as follows:
- 2-Gang Electrical Switch Box
- 15 Amp Toggle Light Switch
- 15 Amp Duplex Outlet
- Outlet to Socket Lamp-Holder
- 2-Gang 1-Toggle/1-Duplex Wall Plate
- Short Length Romex or 14 Gauge Solid Core Wire (< 1 ft. / ~30 cm)
- 3-Wire Solid Core Appliance/Tool Cord
The tools required are:
- Philips and Flat Head Screwdrivers
- Wire Cutters/Strippers
- Hacksaw (Optional)
To begin, I removed the nail mounting points from the switch box using a small hacksaw. If you aren’t cheap like me and bought a more expensive box, you wouldn’t have to take this step, but here we are.
Next, it is necessary that the top and bottom outlets of the duplex outlet are electrically isolated from each other. This is done by cutting the metal bus bar connecting the two screw terminals, which will disconnect the terminals from one another. This is done on both sides of the outlet and is illustrated in the photos. I used wire cutters to cut and remove the piece of metal connecting the terminals, but
using needle nose pliers to grip and move the piece back and forth may also
work to weaken and break the metal.
Now comes prepping the Romex to be used for wiring. First, approximately 6 inches (~15 cm) of Romex is cut, and the outer insulation removed. This leaves three wires, white (neutral), black (live), and bare copper (ground). Approximately ¾ inch (~2 cm) of the live and neutral wire insulation is removed on each end of the wire. Now with wires, outlet, and switch box prepped, next begins wiring.
I have created a basic “schematic” (more of a grade school level drawing) of how the dim bulb tester is wired. Note: I did not use a solid core appliance cord for my dim bulb tester, I would recommend against this as it is not as secure of a connection as solid core is. I first inserted the appliance cord into the switch box and tied a knot in the cord so it couldn’t be pulled out. I then wired the live wire from the appliance cord to the bottom terminal of the switch. Then using a piece of white wire from the Romex, wired the other terminal of the switch to the bottom outlet’s live terminal.
The bottom outlet’s neutral terminal is then connected with the black piece of wire from the Romex to the top outlet’s live terminal. The neutral wire from the appliance cord is then connected to the top outlet’s neutral terminal. Now, the bottom outlet will no longer function as a normal outlet, as it will be a pass-through for live current; any component, in this case an incandescent bulb, will be in series with whatever is plugged into the top outlet.
To finish, the ground wire from the appliance cord is connected to the ground terminal of the switch, with the copper wire from the Romex also being connected to the same terminal, and then connected to the ground terminal of the duplex outlet.
The wiring is then bent to conform better to the interior of the switch box and both the switch and duplex outlet screwed in. With the face plate then screwed on, and the outlet to socket converter plugged into the bottom outlet, and incandescent bulb screwed in, the dim bulb tester is complete. Plugging my dodgy Marantz 1060 into the top outlet, pressing the Marantz’s power button, and then flipping on the dim bulb tester led to a dimly glowing bulb. Now to find the issue and fix it…
A big thank you to EMULSIVE, and DIY Photography for publishing this article!
Panoramas: a great format for (in my opinion) most
photography. Dramatic landscape? Make it panoramic. Artsy architectural photo?
Panoramic. Wanna make that softball game look a little more like Ben-Hur?
Panoramic of course. Weddings? Well… never mind. So as a panoramic
enthusiast, and someone who enjoys shooting film, I’ve had my eye on several
panoramic film cameras. Unfortunately, a true, full panorama camera can be very
costly, like the Hasselblad XPan (>$3,000) or the Fuji GX617 (>$2,000).
There are also swing lens cameras, which use a mechanical method of capturing a
panorama. The lens of the camera pivots or “swings” in a horizontal arc,
exposing the film to the panorama as it moves. This mechanical motion can add
distortion to photos which may be a desirable effect for some. A handful of
companies produced these cameras, like the Widelux F7 (<$1000) used notably
by Jeff Bridges behind the scenes of his films, or the more affordable Horizon
Kompkt (<$200). Regardless, what makes these cameras all true panorama
cameras is their ability to expose the entire panoramic photo onto film. For
example, a standard 35mm film camera exposes an area of 24 x 35mm, meanwhile
something like the Hasselblad XPan exposes 65 x 35mm. This uses more film, but
results in a larger, more detailed image and a true panorama. However, there
exist a type of camera which “fakes” the panorama.
The “Faux” Panoramic Camera
There are many film cameras that emulate the effect of
a true panoramic camera by reducing the area of film exposed to the dimensions
of a panoramic photo, cropping it, rather than expanding it. The Ansco Pix
Panorama (<$10) is a camera that does just that, exposing a minuscule 13 x
35mm compared to a standard 35mm camera at 24x 35mm or the Hasselblad XPan at
65 x 35mm. Along with this, it is incredibly simple, having a static shutter
speed of 1/125, a 28mm fixed focus lens, an aperture of f11 and no light meter
to speak of. The camera is completely mechanical, the film is advanced, and the
shutter is charged by winding a knurled plastic disk. So, with its tiny frame
size, nonexistent settings, this little plastic box is truly a point and shoot;
hardly a Hasselblad. A few simple modifications to the Pix Panorama would go a
long way to improve it.
Yes, this camera even
lacks a tripod mount. Something as simple as using a tripod alters how I take
photos with any camera, as I spend more time framing and adjusting shots. Now,
since the shutter speed of the Pix is 1/125, handheld daylit photos should be
just fine but having the option of using a tripod is better than not having it,
so I made a mount. The design for it is very simple, in Autodesk Inventor, I
made a trapezoid with a hole in it. This hole is a little smaller in diameter
than a ¼” brass nutsert. I 3D printed this mount on an FDM printer using PLA
filament with 100% infill. When the mount was finished printing and removed from the print bed, I
moved it to my bench and used some forceps to hold the nutsert over the hole. I
heated the nutsert using my soldering iron, applying a small amount of
pressure. As the nutsert heated it melted the PLA and buried its way in and
when it was flush, I removed the soldering iron and let it cool. With the mount
complete, I then adhered it to the bottom left side of the camera using double
sided tape. Glue or epoxy would work too but I wanted something less permanent,
as I may alter the design in the future. Although simple, this worked quite
The tripod mount,a 1/4” nutsert, and the tools used.
Heating the nutsert.
Applying a bit of pressure.
Nutsert is nearly flush.
Bottom of the mount covered in double sided tape.
Mount adhered to the bottom corner of the Pix Panorama.
CAD model of the tripod mount.
Filters may not be the first thing to come to mind
when modifying such a basic camera. However, since this camera lacks any kind
of control for exposure, the use of an ND filter would never be more
appropriate. In addition, using color filters when shooting black and white
film can enhance aspects of a photo. Whether it be a red filter to boost contrast
or a yellow filter to bring out clouds, using filters would be a beneficial
addition. Back in Autodesk Inventor, I designed the base of the filter holder
to conform to the curved face of the Pix Panorama. I then designed the part
responsible for holding 58mm filters. The filters are held in place by two
small “fingers” 180° apart from one another, the distance between them is a
little less than 58mm, meaning the filters fit snugly in place due to friction
but can be easily changed. Like the tripod mount, both filter mount models were
printed in PLA at 100% infill. I made the choice to print this using a matte
black filament, so it absorbs light, as it’s being placed around the camera’s
lens. In my mind, this will mitigate the chances of light reflecting oddly into
the lens if using white or another light-colored/colored filament. Once the
models were printed, they were removed from the printer and brought to the
bench where they were adhered together using WELD-ON 4, one of the best
solvents I’ve found for adhering PLA together. Likewise to the tripod mount,
the filter holder was adhered to the front of the camera using double sided
tape. Once installed, the inexpensive set of Neewer 58mm filters that I use
could be mounted and changed with ease.
The two parts of the lens mount and WELDON-4 solvent.
The two parts now adhered together.
Bottom of the mount now covered with double sided tape .
Filter holder installed on the front of the Pix.
A red 58mm Neewer filter installed on the Pix using the mount.
CAD model of the base of the filter holder.
CAD model of the top of the Filter holder.
Much like my life, I expected loading the Pix Panorama
to be easy, however disaster struck almost immediately. When loading the camera
with film, for reasons unknown, I didn’t believe the film was winding properly,
so I hit the rewind release and rewound the film… completely. I wasn’t planning
on doing this, I thought I could rewind it just enough to leave the film leader
exposed and then try again. Nope. Normally saying goodbye to the film leader
wouldn’t be so bad, as I would pull out another roll of film and save the
process of retrieving the leader for home. Double nope. Not only was I an hour
or so away from home, I also didn’t bring an extra roll of film. In a panic, I
began trying everything to recover the leader, using my Leatherman to cut up
bits of random plastic and cardboard found in my car to make a makeshift leader
retriever but nothing was working. About to give up, I realized that I could
turn my jacket into a makeshift darkroom bag by zipping it up, sealing both top
and bottom openings by rubber-banding them closed and sticking my arms through
the sleeves. Before doing this, I loaded the jacket darkroom bag with the roll
of film, the modified Pix Panorama, and my Leatherman. Once my arms were in, I
was able to pop one cap of the film roll off using the Leatherman’s bottle
opener tool, remove the spooled film just enough to feel the leader, and slot
it back through the opening slit in the case. I popped the cap back on best I
could and proceeded to load the camera with the roll. With a few prayers said,
the camera was removed from the jacket darkroom bag, and was ready to shoot.
Fortunately, it appears my Macgyvered methods to load
the camera worked. I shot a roll of Ilford HP-5 Plus which I developed in old ID-11
developer. The age of the developer likely contributed to the grain seen in the
photos. Regardless, I’m quite satisfied with the outcome, even if they aren’t
“true” panoramic photos, the effect is still impactful. The Pix Panorama also
has unique focus, with it being sharpest in the center and some blurring and
vignetting in the corners. The use of various colored filters achieved what I
wanted, and the tripod mount was incredibly helpful. So, in the end, is there
really any reason to use, let alone modify a camera like this? Absolutely. I
had a great time designing the parts for it, and I had an even better time
shooting and developing the film, even with the initial mishap accounted for.
Being able to change out filters was made easy by the filter holder, and many
of the photos were taken with the camera on a tripod. While it certainly isn’t
a Hasselblad or Widelux, it’s still is a distinct and fun camera.
The Final Product
Sample Photos Using Ilford HP5 Plus Developed in ID11 Developer
A big thank you to PetaPixel, EMULSIVE, and DIY Photography for publishing this article and Hackaday for covering it!
About the Camera
Released in 1971, the Polaroid Big Shot was a funky, green
plastic camera that was built for one thing: portraits. The plastic behemoth
is simply designed, using a fixed focus 200mm, single element plastic meniscus
lens. The grip has a stereoscopic rangefinder integrated in it, which makes
framing and achieving focus easy. Focal length is fixed at approximately three
feet, emphasizing the portrait centrality of this camera. The shutter speed is
a static 1/52 second, combined with an adjustable aperture of f56, f36 or f24.
A small aperture and rather slow shutter speed meant most “normally” lit photos
would be underexposed, especially indoors, so most photos would require the use of a flash. For the flash the Big Shot uses Magicubes, which are an explosive, four
use, disposable flash cube. There is a large Fresnel diffuser for the flash
that is built into the front of the camera, which softens shadows and makes the flash much less harsh. A favorite of Warhol, he used the camera to shoot dozens of
portraits, often using the resulting Polaroids as basis for his screen-printing
The Film and The Problem
The Big Shot consumes Type 100 Pack Film: a ten shot, peel
apart instant film produced by Polaroid from the early 1960s until the
mid-2000s. Fujifilm also produced a version called Fuji 100C, which was
discontinued in 2016. This discontinuation marked the death of pack film and
consequently, the cameras that used it. Prices of the now expired Fuji 100C are
incredibly high, often fetching over $100 for a single pack. There is an effort
by SuperSense, a small Austrian company, to produce and sell Type 100 film
called One Instant. Offered in color and black and white, this peel apart film
is priced at $50 for three single shot packs: a great product but still quite
costly. As mentioned earlier, the Big Shot uses disposable Magicubes for its
flash. New old stock Magicubes can easily be found on eBay for cheap, but a
reusable option would be preferred, as it’s likely to be less expensive. So, to
conclude, you can shoot expensive, expired Fuji 100c or new, similarly priced
One Instant in your Big Shot, both averaging over $10 per shot. And when using
a flash (most of the time shooting), new old stock Magicubes found on eBay,
garage sales, your grandparent’s closet, etc. will have to suffice, potentially
adding to the cost. This is all a little discouraging for someone who wants to
experiment with the Big Shot, rather than have it collect dust on a display
shelf. All hope is not lost, well, not for this at least.
There are still many affordable and available instant films
being manufactured currently. One of these films, is Fuji Instax Wide, used in
Fuji’s popular Wide series cameras. It can be found for around $10 a pack
containing 10 shots, relatively cheap… and encouraging! Type 100 Pack Film has
a size of 108mm x 83mm, while Fuji Instax Wide is 108mm x 86mm. See what I see?
A measly three millimeters is all that’s stopping us from cramming our Instax Wide into the Big Shot! However, there are a few other things to consider before
we cram our Big Shot full of Instax. To start, film size just refers to the
dimensions of the piece of film; it includes the dimensions for the chem pack
and film border, not just the size of the exposure. Nor does this dimension include
the size of the plastic housing the film is held in. Moreover, Instax is 800
iso, much faster than typical Type 100 packfilm, which was commonly 100 iso.
Unfortunately, unlike Type 100 packfilm, Instax doesn’t produce a negative,
only a positive. There are plenty of other differences like color, chemistry,
etc. but those are inconsequential for our purposes. Regarding the
Magicubes/flash, various electronic flash conversions were sold at the same
time as Magicubes. These are just like any other basic camera flash; however,
their trigger is designed to fit a Magicube mount. One of these conversions is
called the Acme-Lite 138, which uses standard AA batteries, which are much
cheaper and easier to find than Magicubes. I purchased one on eBay for $15, but
there are many other models that accomplish the same thing, all which can be
found online for not very much money.
The Acme-Lite 138
The Acme-Lite 138 attached with gaffers tape
Potential Solutions and Design
So, we’ve found a current, inexpensive, instant film and a reusable flash, now what? Can we just stuff a pack of Instax Wide in the back of the Big Shot and call it a day? Well, although a bit brutish, it does work. A pack of Instax with its plastic housing is just slightly larger than a pack of Type 100, so it won’t sit perfectly, making closing the back cover a challenge. I did manage to take a few photos using the following method: The Big Shot and Instax is brought into a darkroom or a darkroom bag. Removing the Instax from its protective baggie, the sheet of plastic in front of the first slide of film is then removed. The Instax is then loaded into the Big Shot, with the film facing the exposure area and centering it as much as possible. The rear door is closed, but it requires a bit of force, since the Instax pack is a bit larger than Type 100. Once closed and removed from the darkroom/darkroom bag the Big Shot is ready to take a photo! After the photo is taken, the Big Shot is brought back into the darkroom/darkroom bag to remove the Instax film pack. The Instax can now be loaded into any Fuji Wide instant camera. Once the Fuji Wide is loaded it can be removed from the darkroom/darkroom bag, the lens covered, and then a photo is taken. Covering the lens makes sure the film will not be re-exposed, but it does send it through the rollers of the camera, bursting the chem pack, thus developing the shot. This sounds like a long process, but I was able to transfer film between the Big Shot and Fuji Wide in under a minute. The results I obtained using this method were good, however I noticed a black bar on the top of the photos. This is from the film not being lined up exactly with the exposure area. Although this method works, if I continued to do this, likely the rear hinge on the rear door of the Big Shot would break from the stress of the larger Instax pack pushing on it. Also, I couldn’t remedy the black bar caused by the Instax film not being perfectly lined up with the exposure area.
Loading the film
Developing the film
Building the Film Mount
Because of these issues listed previously, I thought shooting a single piece of Instax film instead of placing the entire pack of Instax into the Big Shot would work much better. However, if a single piece of Instax film is placed in the exposure area, it’s bound to move and fall out of place, as there is nothing holding it. What’s needed is a film holder, so let’s make one.
Tools and Supplies
- Printed Film Holder
- Scissors/Exacto Knife
- Glue/Glue Stick
- (Optional) Black Permanent Marker
The film holder is rather simple, and it can be made from a variety of materials. I used black chipboard that’s approximately 1/16” (1.5mm) thick but any thin cardboard with a similar thickness will do (think cereal box). The template provided can be printed on standard 8.5 x 11 paper, pasted/attached to the cardboard, then the pieces cut out and glued accordingly. When printing out the template, make sure to print with no margins, so the dimensions are accurate. The black permanent marker can be used to color the cardboard/film holder black so it absorbs light, not necessary but it may improve results.
Using the Film Holder
So, we’ve made our film holder, now to use it! Forgive me to those who thought this would be as simple as loading, shooting and voila, a nice instant photo. The process is much more of, well, a process and unfortunately requires a few more steps than the previous method but is very similar, so apologies for the restatements. Like before, the Big Shot, Fuji Wide, Instax, and film holder is brought into a darkroom or a darkroom bag. If using a new pack of Instax, it is removed from its protective baggie, the sheet of plastic in front of the first slide of film is then removed and a slide of film is then withdrawn. Although tricky, withdrawing the film by gently pressing on it with both thumbs and sliding it up and out of the slot at the top seems to be the best method (make sure your hands are clean!). The piece of film is then placed in the film holder, making sure the exposure is facing out. The holder is then placed into the Big Shot and then closed. The pack of Instax can be loaded in the Fuji Wide for safe keeping, as to not expose the film. Once closed and removed from the darkroom/darkroom bag the Big Shot is ready to take a photo. After the photo is taken, the Big Shot is brought back into the darkroom/darkroom bag to remove the film holder. The film is then removed from the film holder and slid back into the original pack of Instax, making sure the chem pack is facing up. The Instax can now be loaded into any Fuji Wide instant camera. Once the Fuji Wide is loaded it can be removed from the darkroom/darkroom bag, the lens covered, and then a photo is taken. Phew! As I said a lot of repetition and many a step. However, the included images should hopefully illustrate this better than my word salad can.
Unloading a slide of film
Loading the film in the film holder
Unloading the film in the film holder
Reloading the film
Developing the film
Tips For Shooting
The use of a dedicated light meter or meter app is handy
when shooting with the Big Shot, although you don’t have much control. As
stated previously, Instax is 800 iso, the camera’s shutter speed is a fixed
1/52 second, and the aperture is only adjustable to f56, f36 or f24. When
shooting indoors, a flash is almost always necessary. Daylight shots with no
flash are certainly possible, and I’ve included some below. Speaking of flash,
since the Acmelite is much larger than a Magicube, I had to adhere it to the
camera using gaffers’ tape, not elegant, but very functional.
I’ve included some photos taken using both “techniques”
described. Although a little involved, once you’ve got the hang of it, the
process isn’t too bad, and the results are quite unique, especially for instant
photography. I’m sure this process can be applied to other cameras that use
Type 100, although I haven’t tried it on anything other than the Big Shot. Hopefully
this encourages some out there to experiment with these methods and get some
interesting photos on a Big Shot or other “obsolete” cameras.
Using Film Holder and Acme-Lite 138 (No Black Bars)
Nosferatu was a fantastic model
The camera loves him
No Film Holder and Magicubes (Visible Black Bars)
I look worse than Nosferatu
I still look worse than Nosferatu
Daylight Shot and No Film Holder (Semi-Visible Black Bars)
Portrait shot with no flash outside
Another portrait shot with no flash outside