![]() I'd look for around 100-110 volts of zener breakdown voltage. So if you need to drop 95V normally on these zener dump circuits you need to up the voltage about 10% or so. In full roar feedback sustain you'll be in the 150 to 200 ma range. You'll be operating the zeners at around 50ma for the power tubes and another couple three for the rest of the circuit. Off the top of my head I think you'll be biased at 22-26ma per pair. You are operating the zener at it's breakdown voltage.Īs the bias voltage is 12.5 I'm going to make a wag that you are using either 2 or 4 El-84. If they had one whisker on the polarity band they would be cathode polarized. In the end it's just better to order a PT with the voltage you want from Phil at Heyboer.Īs drawn the diodes are reverse anode as Mark said. If you search long enough you'll find me talking about doing this very thing with darlington transisitors sourceing regulation voltage through strings of 1 watt zeners. I think it's better to just to stick a tube in there OR put a fairly high DC resistance choke in series with the center tap. ![]() It's a band aid that we often use to utilize transformers originally designed for 5U4 rectifiers with SS full wave rectifiers. And it's going to buck which ever winding it's polarized to conduct.Ī bigger problem as I see it is who wants regulation of a guitar amplifier power supply? Sag and cap stiffness and transformer coil inductance all work together to shape the sound. So it's only going to conduct on half the cycle. Thing is, at the center tap of the transformer is AC. And, that is why marking a diode on your PC board with the plus sign (+) is not good practice.Mister Fowler is of course correct but that doesn't mean that buying a cathode stud won't work. However, with a zener diode, or TVS, it’s not necessarily true. For the common barrier diode, or rectifier, it’s a pretty safe bet. Because it’s not always true that current flows through a diode from the anode to the cathode. For example, A “+” or “-“ sign isn’t good enough. Relying on +, – or _ are not definitive in what they indicate and are not recommended. If you are producing your board without silkscreen, you can put the mark in the copper layer, or submit a clear assembly drawing with the other board files. An “A” adjacent to the Anode on the board works too, though it’s less commonly used. “K” is used because “C” could imply that the spot wants a capacitor. ![]() You may also place a “K” for Cathode adjacent to the cathode. The preferred method is to place the diode schematic symbol in the silk screen. To ensure the best accuracy, we recommend extra care in marking your diodes to remove any ambiguity. Guidelines for diode polarity mark silk-screening - the diode symbol, “K” for Cathode or “A” for Anode or. When you start looking at the CAD libraries, you not only have all the differences from that manufacturer, you may also have different markation schemes from each CAD package developer and from each library builder. ![]() It all depends on whether the diode is a rectifier, an LED, a uni-directional TVS, part of a daisy-chain and a host of other considerations. Barrier diodes can be either orientation. LEDs are usually cathode negative, while zeners and uni-directional TVS diodes can be cathode positive. If you use surface mount diodes or LEDs, you probably understand the challenges involved in correctly and consistently indicating diode polarity. A key element of that accuracy is our understanding of your board and the component markings. Have you ever had an LED or other diode placed backwards? PCB assemblers work hard to place every component, from the largest, highest pin-count logic chip, down to the smallest passive components and micro wafer scale BGAs, correctly every single time. Duane Benson, Chief Technology Champion, Screaming Circuits
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