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I'd like to experiment with a solid state rectifier and I've bought a 3amp, 1000 volt bridge rectifier. Is this the correct rectifier for my 18W plexi?. I've seen applications using 4 diodes and others with just 2 and also heard this depends on if the transformer is center tapped. Any advice

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zep junkie

If you just put in a solid state rectifier like that, your B+ will go up to around 400V. Are you sure your EL84s are tough enough to handle that? Sovtek EL84Ms are suitable, as well as 7189s or 7189As. You will then need to change the bias resistor on your EL84s, so that they don't melt down. Also you will need to increase the value of the dropping resistor (ballast resistor) which feeds power to the PI and preamp, so that the PI and preamp voltages stay the same. Alternatively, you could hook up some zener diodes (or a VVR) to bring the whole amp's B+ voltage back down to around the 340V, where it should be.

As the 18W PT is centre-tapped, you need to use a pair of silicon rectifiers. Since you've bought a bridge, you can use half of that to give you the pair. The two ~ connections on the bridge would go to each end of the PT secondary, and the bridge's + connection goes to the first filter cap and standby switch.

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Great tones come in small glass jars!

Be careful when doing this. I agree with Phil, drop that B+ with a zener when using a SS rectifier, an use only half the bridge, not all four.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

thanks. I do have 5 9volt 5watt zeners as well that I'm planning on using as needed. Although I have to say that the negative feedback mod(posted a few weeks back) has really tightened things up considerably. This in conjunction with a few preamp tweaks has brought the amp closer to a mini version of my72' 50 watter....this is good news for neighbors and ears. Just like to say thanks again, this kit was a blast to build and great fun tweaking to my tastes, best value hands down.

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zep junkie