At last the power adapter for my guitar amp ready. My Radio Craft book has been announced no major difficulties for the power supply, but for various reasons, the simple power supply from the wiring diagram is not so very timely.
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| In the foreground, the half-finished board for the heater voltage of the preamp tube, followed by the indirect grounding a 1000V capacitor and 2 resistors. |
Nowadays, the circuit ground can not be connected directly to the ground to avoid ground loops between multiple devices. The capacitor also filters out high frequency voltage components.
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| to see: The Schottky diode of the rectifier. Yes, they are recycled and have been installed somewhere - but 95% of the remaining parts too ;-) |
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| Here are the indirect grounding. For wiring, I'm mostly switched to rigid NYM cable. This can not fray and is easier to process - easier to stuff, especially in terminal strips. And it must not previously tin :-) |
The preamp tube to be supplied with DC voltage - instead, as indicated in the schematic, with AC. I hope that by the hum is reduced to a minimum. To this end, I build a small circuit board with rectifiers (Schottky diodes fast :-), jder amount capacitors for smoothing the voltage and a 5V voltage regulator (7805), to be "highly placed" with two diodes to 6.2 V:
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| Not pretty, but stable: The finished Heating Voltage board. |
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| the board on their makeshift "legs". Is more stable than it looks. Really. Just think ;-) |
When connecting my test tube, turned it into a light bulb because I had a defective 7805 oO used at the output were at 23 volts instead of the expected 6.3 volts. The tube still works the way a transistor :-) I could throw away after only ^ ^
So rummaging in the junk box -. Not 7805 anymore :-( So reschedule the LM317 adjustable voltage regulator circuit this, I had to modify something. so that the board then looked like this:
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| If it :-) Just a little turn on the trimmer ... |
the value for the resistance of the trimmer with the beautiful blue insulation I had to try (230 ohms is good) but because I can not switch formulas: - [If they can indeed still make time in their data, but Noo ... naja so it went well ^. ^ The resistance determines the setting for the trim pot.
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| 6.43 volts at cold filament. MAY Resistors are experimentally ;-) Determine |
The output tube, I'll provide you with AC voltage at 350 volts plate voltage is not to continue, relieving the voltage regulator so that it can not be excessively hot. Now it can
go at last to the amplifier itself :-)
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