Search results

  1. Y

    Need help understanding 70.7 Volt Line Audio

    After reading about Low Impedance (8 Ohm) Audio Output vs.70.7 Volt systems, I still have questions. I know with an amplifier driving an 8 ohm speaker, a transformer is used to match the speaker (8 ohm) to the output impedance (load resistance) of the output stage/ driving tube or...
  2. Y

    2A3/ VT4-C Amplifier Design help

    I want to build/rebuild and amplifier using (2) 2A3 Tubes driving (2) VT4-C Tubes. This is a rebuild of a AM Modulator, similar to an Audio Amplifier. I found this inoperative chassis , with this tube line-up, but the bias circuits are missing, and I have no schematic. The audio...
  3. Y

    Need help with design

    Experimenting with "vintage" radio circuits I find myself in need of various high voltage supplies,typically in the range of 250 to 650 VDC. I have several industrial type transformers designed to boost 120 to 220 VAC and, 220-440 VAC, at several amps. These were used for...
  4. Y

    LED TV BACKLIGHT

    I’ve been experimenting with a defunct 55” LG LED tv. For which I have no schematic. Initial failure was screen black, no picture. I’m trying to learn here. I believe the black plastic panel which connects to the Timing Control Board is a multi array of LED filters. Is this panel the name...
  5. Y

    PCB, Toner transfer method

    i’ve decided to try making some PC boards using the toner transfer process (using laser jet printer). The process calls for using multiple passes through a laminators To transfer the image from paper to the copper. An alternative is to use a clothing iron. Another thought is to use a hot...
  6. Y

    Need help choosing a substitute regulator component

    I have a Conar power supply, Model 320. It uses only a few compnents: full wave bridge, transformer, a few capacitors, and a 4 terminal IC (UA 78HG), T05. Package. Pos. Voltage regulator. I’m having a difficult time finding the UA 78HG. ( four terminal, variable, pos voltage regulator) I...
  7. Y

    Ford Flat-Pack Ignition Modules

    I would like to build a test circuit for Ford flat Pack Ignition modules. The module has (2) pin terminals for input and a standard spark plug connector on the opposite end. The module grounds to chassis when bolted to the engine. On a known "Good" Coil, I measure very low...
  8. Y

    Weston Technology Remote Display Unit

    I found this Remote Display Unit, it also has a LC/SDCM Serial Data Converter Module (for use with DayStar NOVA LCD). I have the following information: There are (4) terminal connections: Power Supply Return, 5V Power Suppply, RS-232 Return, Receive DATA. It is a receive -...
  9. Y

    Thermocouple RF Ammeter

    What is the characteristics of the thermocouple device used with a thermocouple RF ammeter? I have several meter movements labeled in RF Watts, but missing the probes. Are these typically J or K type thermocouples, or thermopiles? Or, are they shunts with a thermocouple...
  10. Y

    Inductor/power supply choke operation

    I'm familiar with the formula for Inductive Reactance, and realize Inductance, is directly proportional to frequency change . I also know as the DC current increases the Flux increases until saturation . At saturation (critical) Inductance is .at a minimum because the Flux no...
  11. Y

    Filter Choke for power supply

    How does one calculate the value of a filter choke used in a dc supply. I want to build a dc 600vdc supply , pi filter, full wave bridge rectifier, 60 Hz mains supply . I have 47Ufd 800 VDC capacitors. How do I calculate inductance for the choke.
  12. Y

    Zener Diode Design

    I’m trying to understand how the component values are chosen for a battery eliminator circuit by reverse engineering. Original Design: Vs supply +140 V (6) 22V 5 watt Zeners In series (5) 1N2007, (.7 X 5 +3.5V) forward biased in series (1) 300 ohm 3 watt resistor (Rs) in series A 70...
  13. Y

    CRT High Voltage Power Supplies

    With CRT supplies, why do some circuits ground the positive and others ground the negative. Does making the cathode several thousand volts negative make the circuit physically safer, or are there other reasons. It seems most oscilloscopes use negative HV referenced to ground...
  14. Y

    British Electronics correspondence course

    I found this little scope and schematic, and had fun restoring to operation. Does anyone know of the associated correspondence course. The scope has various outputs ( time base out, power supply, deflection plate direct connection points, etc. I would like to see the...
  15. Y

    Transmitter Pi Tuning and Loading network design

    I’m trying to get an understanding of how Pi Output tuning circuits are designed. It appears most radio transmitters are designed for a 50-75 Ohm load. Why is this? I’m thinking when coupled to an antenna, the loading control would be resonating it’s capacitor reactance with the inductance...
  16. Y

    How is transformer impedance selected here:

    I've seen a speaker (4 ohms) connected to a 4: 25,000 ohm input transformer . The 25K side is in series with a 500K pot which the center tap feeds the grid of a 6AV6 tube/valve. This is for an intercom circuit. I'm wondering how the transformer ratio and pot values were...
  17. Y

    Cathodic Protection

    I am some what familar with Cathodic protection as applied to metal buildings, ship hulls, etc. Typically the structure we are trying to protect is considered the cathode, and an external anode material is connected by wire to the structure. The anode is sacrified...
  18. Y

    Cathode follower circuit for Rf generator

    I revived from my junk box, two military frequency meters: A CRR-740 (LM-13) and a BC221AA. I built Ac powered battery eliminators for each unit ( 180 VDC and filament source.) I’d like to build a cathode follower for each unit so I can pick off signals for my frequency...
  19. Y

    Power Supply Capacitors

    I am building a variable DC power supply for experinenting with vacuum tubes. It will be 400Volts 150 mA output, full wave, semiconductor diodes, using a pi-filter with a choke, and possibly swinging choke. My plan is to use a Variac on the primary so I can vari the...
  20. Y

    Pie Network , Transmitter Tuning and Loading Questions

    Pie Network Transmitter Tuning and Loading questions: From reading texts I am aware that a pie network is needed to match the load (antenna) to the source (tube circuit). I also am aware when C2 is unmeshed( minimum capacitance) , it’s reactance is highest and maximum current from the tank...
Top