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Tech Forum

Oil Filled Caps August 2017

I’m trying to bring an old tube transmitter back to life. The power supply uses oil filled capacitors, which don't seem to have handy replacements. Assuming that I can change the oil to reduce the leakage current, what kind of oil is used?

Will motor oil work, for example?

William Helm
Eugene, OR

Laser Color Choice August 2017

I want to convert a 3D printer to a laser burning station to work with wood veneers and leather goods.

Any advice on the best type and color of laser to get? I’ve heard brown wood and leather reflect more red light and so I should use a blue laser.

Kyle Hoyos
Walkerton, IN

Unknown Power Supply For Monitors June 2017

I have three mini monitors but no power supplies, and would like to know what power supply to use. I have tried one of the three monitors using a 12 VDC at 500 mA supply and it came on for a nanosecond.

Since then, I have tried the same monitor several more times with the same supply, and also using my car’s battery, my lawn tractor’s battery, and even purchased and tried a 12 VDC at 1A supply all with the same results.

What is the power requirement for such mini monitors? I don’t want to burn any of them out using the trial and error method.

M Williams
St John, IN

Salt Sensor July 2017

I have a water softener that needs pellet salt added to a brine tank. I’m trying to figure out a circuit to detect when I need to add salt as the tank is opaque and salt usage varies depending on use. The simpler the circuit, the better!

Salt Sensor
Greensboro, NC

What To Do With Leaded Solder? June 2017

I have a bunch of 2 lb rolls of leaded solder that I no longer plan to use, given the availability of lead-free solder. How should I dispose of the solder? Is it considered hazardous waste due to the lead?

Derek Raya
Derek Raya

Laser Eye Protection July 2017

With high powered laser prices dropping like crazy, I decided to pick up a 3W blue laser from eBay for $50 to experiment with.

I’m concerned about eye damage and would like some advice on eye protection. What makes a pair of laser goggles good and what should I stay away from?

Gary Byrum
Milwaukee, WI

Sequential Turn Signals June 2017

The simple way to do an automobile three-light sequential turn signal is to let the blinker turn on bulb #1 and then the circuit will do #2 and then #3; not a problem.

The problem is the brake lights that use the same filament in the bulbs. Hit the brakes so left and right will sequence once then stay lit, unless you hit the brake again.

Same with turning. One side sequences and if you hit the brake, the other side will sequence once and then stay lit while the turning direction is still sequencing. However, if you hit the brake, both sides will sequence once and then stay lit.

Proper function can be accomplished because aftermarket kits are available that do it correctly. Unfortunately, they are very expensive.

No matter what I think of, I cannot come up with any logic circuit that would prevent the brake indicator from sequencing once, i.e., blinker ON-OFF 12V, brake ON 12V; brakes only, ON 12V both sides.

Any simple ideas? Hope I do not need to program an IC. Guess I can always learn at 72 years old. Started reading N&V when it first began. Love it.

Daniel Zielinski
Port Saint Lucie, FL

Do Good Kits Come From China? May 2017

I’ve seen extensive electronics kits based on the Arduino and other processors on Amazon for essentially the cost of a bare Arduino. Are these kits — presumably made in China — any good, or is it a “You get what you pay for” type situation?

Christopher Neville
Richmond, VA

Miniature Parts Needed June 2017

I’ve been tearing down Seiko solar quartz watches in search of small efficient engines to power miniature robots. Can anyone recommend a source for additional components, such as miniature axles and wheels?

Naja Heilmann
Norcross, GA

DMM vs. AVOM May 2017

I do mainly audio work and have been told by a few old timers that analog VOMs are the only way to go for testing and tuning gear. Problem is, I can get a new DMM for $20 on Amazon vs. an ancient Triplet or Simpson analog VOM on eBay for up to ten times that. My question is: Is it worth it? Would I be better off with a modern Fluke meter with true RMS reading?

Providence, RI

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