Tube Amp Archive

The Zener diodes used most commonly for B+ reduction are the "AK" versions which have the cathode on the case. Just bolt 'em on and the chassis acts as a heat sink. The regular polarity ones ("A") can be used, but you can't bolt them to the chassis, so you need an ungrounded heat sink or a higher w...

So Za= (415-110)/0.215= about 1420 ohms. X 4 for a pair = 5,680 ohms Zaa. Depending on your bias point you might be running very hot. Putting 8k ohms in instead of 5k7 reduces power output dramaticallyand no doubt gross distortion too, so it also makes sense to me that Fender might well have picked...

I just checked the schematic for that amp. No reason the diode trick shouldn't work. You sure about the polarity of the diodes themselves? They make 'em both ways: cathode case and anode case. Either way you just have to make sure the "pointy" end goes to ground. Probably ought to keep the case ins...

I'm stumped too. That should work, There are no other connections from the negative side of the bridge? And you did connect the zeners cathode to ground? Right next to the star ground point, I drilled a hole and brought out a pair of wires for the zener string. This was at a point directly between ...

You can put zeners between the transformer center tap and chassis ground (or the bridge rectifier ground). Get 30V worth of zeneers perhaps 2x15volt 10watt zeners. Piece of cake. I had tried a string of zeners and they did not work on this amp. The string measured 30V on a bench supply, but did not...

This is the simplest way I know to get B+ exactly where you want. I've done it on 2 amps now and it works great. Do you know if it would work on a power supply that has no tranny CT? For example, connect it between ground and the (-) on the full wave (4 diode) bridge? My Trace Velocette has only a ...

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