From FB group Building Transistor Radios 2018-08-24 – The discussion was about the OTL complementary symmetry audio amplifier that Mr. Barnett has posted several times to the group, which uses a 2N3904 and 2N3906. Willie Barnett Let’s talk about current. Suppose your amp has a 9V supply. When the output transistor is turned fully on,
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Also photo posted to FB group Building Transistor Radios. I got several of these Wien Bridge Oscillator kits from an eBay seller in China. They are built using the circuit from http://redcircuits.com/Page13.htm More information can be found on the wiki for this oscillator. The kits come with no instructions, so to assemble it, use this red circuits
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From a reply on FB I built a speaker for a swimming pool. It was a large can of steel with an audio transformer mounted inside. The ‘I’ laminations were removed so the ‘E’ laminations could be very close to the end. I drove it with a 2N3055 on a heatsink. The secondary winding must
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I bought several of these miniature audio transformers from Electronic Goldmine. They are encapsulated so I can’t see anything, windings, core or materials. There are 5 pins, 2 on one side and 3 on the other, but the center pin measured open, so it’s apparently there to make sure the transformer is inserted the right way. The
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A few weeks ago I ordered an ultrasonic dog repeller from an Asian dealer and it finally arrived this week. It wasn’t very expensive. I think one reason why is because this product has never been scientifically tested to prove that it works. The reason I say this is that this product apparently is not
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When you get a 70.7 Volt Public Address Transformer, you see that it has connections for different speakers, such as 4, 8, and 16 ohms. On the other winding are various taps for different power outputs such as .625, 1.25, 2.5, 5 and 10 Watts. But there is nothing to tell what the impedance is
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This was in a schematic from the 1960s, the days of silicon transistors, before low noise op amps. The 2SC369 is old and very likely to be no longer available. The replacement transistors could be any low noise small signal, such as the BC550C or 2N5088. The supply voltage shown is 34 VDC, but this
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First off, I must state that the PSO is not the best solution for an audio oscillator. It uses only a single transistor, but it has a limitation that makes it put out a poor quality sine wave. As typical of the PSO, the sine wave becomes distorted because the loop gain is greater
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I blogged a schematic on May 15, but it took me until now to build the schematic. I tack soldered the PSO together with the components shown, except I did not use the two diodes and two 10k resistors. First off, according to this article, to get it to oscillate, the overall voltage gain of
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I’ve offered the hybrid transformers for quite awhile, and Chris, KD4PBJ, was the first to get some from me. He constructed a 1 kHz audio oscillator (see the photo), with a .068 uF and .0068 uF capacitor in parallel to tune the transformer to 1.004 kHz. I like the way he laid out the oscillator
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