Modifying Preamp Circuitry

GeoK 3 years ago Reply If you really want to make something REALLY dangerous manufacture a few capacitors utilizing 55 gallon poly drums with the entire outer surface covered with heavy duty aluminum foil very similar to this arrangement then sprayed with truck bed liner for insulation. Pick up a foot roll of 12 awg copper wire and strip it with a sharp blade by tying off one end and walking down the line while holding the blade at the appropriate angle to efficiently remove the insulation at a decent pace. Wrap 5 50 foot lengths of your now bare 12 awg wire around the exterior aluminum foil covered drums in a helical ascending fashion then twist the 5 tails together tightly for a good 4 inches or so to produce a connection point with some respectable high current carrying capacity. Charge them up with a pair of old watt microwave oven transformers The good ones back when they were still called Radar Ranges and you could set up a truly maniacal active burglar alarm system! Salvage the high voltage diodes from the microwaves as well of build a full wave bridge rectifier from high voltage diodes to make use of both ends of the AC cycle, waste not want not. With one barrel charged positive and the other charged negative for a 16, volt DC combined potential difference at that capacity the perp would most likely explode violently when his now airborne corpse was determined to be the path of least resistance for 50 cents worth of electricity unleashed in a millisecond or two! Once it’s all over simply pick up the mesh mat and remove the 4 AWG connecting leads tossing it down in the basement with the barrels and the rest of the gear the call the coroner. It will appear to have been an apparent divine intervention where God himself struck down the intruder with a bolt of lightning! That is probably pretty close to what the event would look like even if the nosy neighbors actually witnessed it unfold, especially at night!

How Capacitors Work

Ask Question Step 7: The Heater Power Supply s Unfortunately, the filament secondary for my power transformer isn’t a separate winding, and doesn’t have a center tap. Maybe I could disassemble the trannie and see if the coils could be separated Placing two large diodes in parallel but opposite directions in an AC supply limits the voltage by the voltage-drop amount. That dropped the filament voltage right to 6.

Oh man, I just saw that you replied to this, Bjorn! I must have had notifications turned off. But okay, so I usually use the Laney on the gain channel, but with the Gain rolled back to around , and Volume up around 11 or noon whatever is needed.

Each tone wheel is a steel disc similar to a gear, with high and low spots, or teeth, on its edge see figure As the wheel rotates, these teeth pass near a permanent magnet, and the resulting variations in the magnetic field induce a voltage in a coil wound on the magnet. This small voltage, when suitably filtered, produces one note of the musical scale, its pitch or frequency depending on the number of teeth passing the magnet each second.

Unlike those organs which produce complex tones and then use filtering to achieve the sounds of traditional instruments subtractive synthesis , the Hammond organ produces nearly pure sine wave tones and then combines these to create instrument sounds additive synthesis. Tone Filtering For this scheme to work, those pure tones must be as close as possible to pure sine waves.

This was achieved by manufacturing the tonewheels with appropriately shaped teeth and then using electronic filtering to remove any harmonics generated by inaccuracies. Of the 91 tonewheels in a Hammond console organ, the filters for tones 49 to 91 consist of a capacitor and an inductor in the form of a transformer. The schematic excerpt to the left shows one such filter. The operation of this filter depends on a number of parameters: Together, these components form a passive bandpass filter.

Only two different capacitor values were used in the tonewheel generator:

Start and Run Capacitor Explained

Motors used in HVAC such as the condensing fan motors or blower fan motors sometimes need help to get moving and to stay running at a steady pace, with no heavy up and down spikes. Not all motors will have a start or run capacitor some can start and run by themselves. Capacitors in HVAC can be separate or can be in a single package.

The Dual Round Capacitors are simply the way engineers are trying to save on space and cost.

If you are testing out your new boost capacitor, be sure you allow several minutes between startups of your A/C. This ensures that pressures within the A/C system equalize and the compressor motor will start much easier. If it’s particulary hot out, the A/C system will have very high pressure on one side of the system after shutdown.

This is not a liability at all as the B is one of the best sounding tubes ever produced. Even if you have highest efficiency speakers, the golden tone of the B tube and extra headroom it provides, are still the safest bet for DHT amplifier success with the most kinds of speakers, especially if they are not horn types. Push- pull B amplification offers the highest output power level of any of the above configurations up to 40 watts per channel or more in some circuits!

For my initial foray into the world of DIY tube amps, I decided to hedge my bets and go with the B single-ended tube topology for higher power and great fidelity. If so, just skip to the appropriate section that you need. Getting your hands on a good schematic is the probably the second most important step in the amp building process.

Unless you are an experienced experimenter and design your own amps, the safest route is to select a proven schematic from many that are offered for free at sites on the Internet. For instance sites like: A great way to start to learn tube audio is to get hold of as many schematics as you can find and study them closely. If you study them long enough, you will begin to see similarities in circuits and their sections from one schematic to another. Try to view an amp as a combination of different stages driver stage, output stage, power supply, etc.

Try to see the forest as groups of trees… Another good way to learn is to get hold of a vintage tube amp and its schematic and spend some time studying the wiring underneath while trying to visualize the circuit flow from input to output. Usually commercial push pull designs are much more complicated than what we would normally build, so if you can figure one of them out, our typical DIY amps will be a breeze to understand and build by comparison.

Guitar Tube Amp

The input stage is biased so that the supply voltage is divided equally across the two complimentary output transistors which are slightly biased in conduction by the diodes between the bases. As the bias current increases, the voltage between the emitter and base decreases, thus reducing the conduction. Input impedance is about ohms and voltage gain is about 5 with an 8 ohm speaker attached.

The term VD is V if you are using a series protection diode. Otherwise it is 0V. The term IL is the nominal operating current in amps. If 20mA, then use If mA, then use The term VL is the nominal operating voltage of the bulb or LED. The nominal operating voltage for an LED is typically V.

Motors used in HVAC such as the condensing fan motors or blower fan motors sometimes need help to get moving and to stay running at a steady pace, with no heavy up and down spikes. Not all motors will have a start or run capacitor some can start and run by themselves. Capacitors in HVAC can be separate or can be in a single package.

The Dual Round Capacitors are simply the way engineers are trying to save on space and cost. They could have put two capacitors in a unit but combined them in a single package. A dual capacitor will most often have one side to start the compressor Herm and the other side to start the condensing fan motor.

The third single leg on a dual capacitor is a shared common leg. A Start or Run Capacitor can be combined into one capacitor called a Dual Capacitor with three leads, but can be split between two separate capacitors. The Start Capacitor gives a fan motor the torque it needs to start spinning then stops; while the Run capacitor stays on giving the motor extra torque when needed. If the Start Capacitor fails the motor will most likely not turn on. If a Run capacitor goes bad then a motor can turn on but the running amperage will be higher than normal causing the motor to run hot and have a short life expectancy.

If the unit has two capacitors then one is the Run Capacitor and the other is the Start Capacitor. Keep in mind the compressor also often needs a capacitor which will be HERM compressor. A capacitor can be bought at a HVAC supply company there a usually at least a few even in a small town, also online Amazon is a good place to look.

Mini BoostPack 12V Capacitor Car Battery

You’ll often hear people say on the radio that their Cobra 29 LTD has had a “swing mod” or “Super mod” done to it. On ebay people often will tell you that the radio they are selling has had a swing modification done to it to make it a “screamer”. So what exactly IS the famous “super modulation” modification? Now this modification is not for everyone, and it does require a little soldering, But if you have an old Cobra 29 LTD or Cobra 25 LTD laying around it’s a fun modification to learn.

It’s one of the most popular modifications to have done to your CB radio. You’ll often hear people say on the radio that their Cobra 29 LTD has had a “swing mod” or “Super mod” done to it.

The flicker adds drama to these living machines. Now that our models can have this dynamic element too, we have another reason why modelling steam is better than diesel! They are just being prototypical! I don’t mean to be a killjoy, but it has been pointed out to me that only oil-fired locomotives have a flickering firebox. Coal and wood-fired locomotives have a nearly constant glow. But flickering fireboxes sure look good!

Parts Connexion

Reply oscar on July 3, at 8: Reply lasersaber on July 3, at It might extend the life of your car battery. It would remove a large part of the cranking amps from the battery when starting the car. Looking through the Internet you can mostly observe watered down information, something like bla bla bla, but not here to my deep surprise.

The Patterson PR was a “Los Angeles-built,” superheterodyne communication receiver that was produced early enough to have many unique or, at least, unusual design features.

Narrative Description of Amplifier Circuit Function This amplifier provides watts power output for the Six-meter band. It uses the low cost GS35B Russian power triode in a grounded grid or cathode driven configuration and requires about Watts of drive power. The Russian tube is currently available from USA and international sources1 at attractive prices, especially when compared to the cost of traditional American tubes of this power rating. The center tap of the filament secondary provides the connection to the tubes bias circuitry.

RF driving power from the transceiver is applied to the tube’s cathode using an input matching circuit. A 5 to pF vacuum tuning capacitor is shown on the schematic. At plate voltages approaching 4kV, this capacitor may be eliminated. The tube circuit can be resonated using the vacuum tube output capacitance in conjunction with the output Pi-network coil. A safe, easy way to adjust the output coil is described in the section “Adjusting the Pi-Network”.

This is also a “set and forget” adjustment. Considerable expense is saved by elimination of the vacuum variable.

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See the FAQ for more information on this very cool feature! You should see your gravatar displayed in all it’s glory over in the sidebar. Don’t have a gravatar?

Back to the GEO Home Page Musical Instrument Tube Amp Building, Maintaining and Modifying FAQ. Much of this material applies to building or re-building hi-fi equipment, as well but it was originally intended for musical instrument crazies.

Some of these features became “standards” for communications receivers while others are only found on the PR and its matching Pre-Selector. Besides its unusual design, the PR has an important place in history relating to radio manufacturing on the West Coast in the s. The PR has always been a favorite of mine, probably because it was the first communication receiver I owned at age fifteen.

This write-up includes circuit details, restoration suggestions and a performance report. Before , radio building on the West Coast was uninhibited and pretty much any type of radio could be built and sold without very much interference from the license-holding and patent-owning radio manufacturers located on the East Coast. California was just too far away and their share of the booming radio market didn’t seem to impact the radio-selling profits enough to enlist infringement-busting lawyers to pursue those who were violating patents.

By , RCA was beginning to assert some control over some of their newly acquired patents. Mainly the “Tuned Radio Frequency” circuit was important at the time although anything resembling a superheterodyne was almost certain to be a target for the radio lawyers, too. RCA was beginning to pressure the Gilfillan Bros.

Sennett and Jay Gilfillan, the only large-scale radio builder in Los Angeles actually in the entire West who also had other assembly plants around the country. The pressure became intense enough that eventually Sennett Gilfillan got on a train heading East with the intention of a “face to face” meeting with RCA officials. Sarnoff easily avoided meeting with Gilfillan for several hours but that just seemed to incense Gilfillan more.

Hammond Organ Tonewheel Generator Capacitor Replacement and Calibration

Fixing and Modifying the Sansui x Receiver Introduction The Sansui x is a good sounding and popular vintage receiver. The A is almost identical and most of what’s here applies to that unit as well. The is also similar, but lacks the handy plug-in power amp board. Unfortunately, one of the small signal transistors used in various places has a history of becoming noisy.

It’s the notorious 2SC LG.

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If the motor on your washer makes a humming noise, but it won’t start, check the start capacitor. You can perform a simple test to tell you if your capacitor is completely dead or if it still has some life left in it. See Step 1 for more information. Steps 1 Remove the start capacitor. The easiest and most convenient way to discharge the capacitor is to attach the terminals of a low wattage v light bulb about 20 watts to the capacitor terminals.

This will safely discharge the electricity which may still be stored into it. Be very careful that you do not short the terminals by connecting one to the other, until after the capacitor has been discharged. Doing so could injure or kill you. Use extreme caution when discharging the capacitor before proceeding. Signs that the top of the capacitor are bulging out slightly, as if expanding, is a sign that the capacitor might be dead. Likewise, check and look for any dark fluid that appear on the top of the capacitor.

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Tube Stuff Suppliers Appendix B. Tube amps have always been the amplifier of choice for the working musician. Musical myth has ascribed almost magical tone to them.

NOTICE:This is Dan’s Internet Catalog No. 11 and all previous on-line Catalogs are no longer valid. This online Catalog No is the only one to other past down loads are not valid and Dan’s will not accept orders from any of them, only Catalog NO

Just what is tone? What is a good tone and how do you achieve it? Which amps you should choose for your setup and how to get the tones you want. Check out part 1 and part 2. Amps People tend to prioritize guitars and a bunch of pedals and forget the importance of a good sounding amp. Choosing the right amp for your setup is crucial for getting the tones you want from your guitar and pedals. I strongly suggest that you buy a guitar and amp before you spend all your savings on pedals.

This will ensure the best fundament for your tones and playing. A tube amp consist of a pre-amp section that takes the small signal from your guitar and amplifies it enough to drive the power amp section. Most amps allow you to manipulate the pre-amp signal with a number of gain and EQ controls. The signal is then fed into the power amp, which gives the power to drive the speakers. The amp could either be a head with one or more speaker cabinets or a combo, with the amp section and speaker cab combined.

How to install a car audio capacitor


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