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  1. alfa88

    Voltage Follower

    I'm finding it hard to believe this circuit isn't working. It's almost verbatim to what's on the datasheet. Without the transistors there is the full adjustment range (1 to~14V). With the transistors the range is 12 to ~14V. I left the capacitors out for ease of experimenting. UPDATE: My bad...
  2. alfa88

    New Power Supply

    My power supply went poof. Turns out the transformer was poorly assembled and the outer windings were able to short against the core. Anyhow I am considering more power. I came across this design. Credits go to Zamboniman60. Feedback anyone? I believe the positive is using a Darlington pair as a...
  3. alfa88

    Wall Wart Question

    I'm reverse engineering a cheap wall wart and I think I have the circuit pretty well traced, One problem I have is some of the diodes have odd numbers D5, D6 and unlabeled 'C11PH' . Another question I have is where is the regulation coming from?
  4. alfa88

    Protron/Spectroniq FSP194-3F01 Power Supply for PLTV-3250

    I'm hoping somebody has one of these sitting around so they can tell me what the value of CS29 is. I pulled it out and got distracted on another project. Doh!
  5. alfa88

    Fluorescent Lamps

    Back to basics. This is the way I thought they worked. The ballast provides a high voltage to get the mercury to ionize and then the voltage drops and the filaments on each side maintain the glow. However, my magnifying lamp wasn't working so I delved into what the problem might be. I made a...
  6. alfa88

    Weird Light Bulb

    I need help locating a weird light bulb. As far as I can gather it most resembles a festoon style bulb only it doesn't have end caps just wires. The length is 1" / 25cm excluding wires, the Voltage is 12. It's for panel lighting so Amperage is probably fairly low (for incandescent) . They have...
  7. alfa88

    Protron/Spectronics PS Schematic(fsp194 3f01)

    Please, please, I'm hoping somebody has a schematic. This seems to be the main problem with this out of business TV brand. The capacitors are apparently underrated and they start venting taking other parts with them. I can muddle through but a 'road map' would help.
  8. alfa88

    High- Voltage Adjustable Regulator

    I'm looking to build a bench power supply to do some vacuum tube(valve) experiments and was wondering if anyone knows of a solid state solution for a adjustable voltage regulator that could withstand 350Vdc input, output 300Vdc @~ 300ma. I got to about the 6th page on Google and start seeing the...
  9. alfa88

    Evolution of Electronics

    I'm wondering if anyone else had heard this story. When Edison finally developed a practical light bulb he observed that there would always be a deposit forming on the glass. That is when he added an additional element to the bulb to try and alleviate the problem. That's when he discovered the...
  10. alfa88

    Wanted: Realistic TM-1000 Manual

    I'm looking for a manual either owner's. service or both.
  11. alfa88

    Vacuumtubes.net

    Has anyone ordered from these guys? They're based in Florida. I did a web order last night and was expecting an Email notification like I get from everybody else. Nothing. Called and was told I'd get a call back.
  12. alfa88

    Braun 99 UKW

    I am looking for a schematic for a Braun 99 UKW radio. I've gone through 2 Google pages so far and will continue to search but just in case someone here has one... UPDATE. Nevermind. Braun so dutifully left a schematic stapled to the bottom of the cabinet. Ah, the good old days.
  13. alfa88

    How To Wire a Staco 1010

    I am 99.999% sure how to wire my new (used) toy but I keep thinking of Murphy's Law. What I gather from a drawing I found is that 120Volts goes to terminals 4 and 5. The output goes to terminals 4 (again) and 3 .
  14. alfa88

    Variac Current Meter

    I'm having a Senior moment. I want to add a current meter to a 10A Variac. My thought is to add a series/shunt resistor and then a rectifier/cap. to the meter. The meter draws 104.5uA @ .05Vdc full scale.The Variac puts out 1 to 140 Volts. What I initially come up with is .01 Ohm @ 1 Watt but I...
  15. alfa88

    Antique Radio Repair

    I'm about to take on an antique radio repair and have been getting some tips. One of which is to gently encase twisted wires in silicon sealer. the theory being that there may be a reason they were twisted in the 1st place (induction). My question is what brand/type should I get and is it easy...
  16. alfa88

    Common Terms

    There are some terms that get used that just seem to bother me. I get the concept it's just the labels that stick in my craw. #1: Flyback transformer. What make it any different from any other transformer? #2 Crowbar. Okay, maybe I'm not so clear on that one. #3 Bootup/ Boot strap. Where did...
  17. alfa88

    Better Late than Never

    Hello all. I thought it about time that I introduce myself after being here a while. My name is Gary and 1st. off let me thank those that have answered my various questions. I would imagine that my interest in electronics began when I was 2 years old when I got a healthy respect for electricity...
  18. alfa88

    Dremel 395 VSC

    My Dremel finally went bad after a sputtering. I can find a replacement switch/control cheap enough but I wanted to make sure it wasn't something else 1st. so I did some research. Hopefully this will help others. Btw the easiest way I found to bypass the board is to pull the control board out...
  19. alfa88

    Tenma 72-6805

    Helllp. I need a service manual or at least a schematic for my poor oscilloscope. My model comes with a built in sig gen. and that's the section that went haywire. The range and function selections are scrolling by themselves.:eek:
  20. alfa88

    Edge Detector

    Edge Detector? I just came back from a job interview and they had me evaluate an op amp circuit. I'm pretty sure I got it right but what do you guys think? On the input was a 2 Vp-p square wave @ 1kHz, the output a triangle wave, 6Vp-p @ 1khz. The negative slope of the output coincided with the...
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