From tremolu–(at)–ol.com Fri Jan 10 15:41:01 CST 1997
Article: 33869 of alt.guitar.amps
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From: tremolu–(at)–ol.com (Tremolux)
Newsgroups: alt.guitar.amps
Subject: Re: 5R4 vs. 5AR4/GZ34
Date: 10 Jan 1997 06:39:10 GMT
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>>>the 5R4 might not be so bad after all and can supply about 250 ma. at
600 volts dc ,

Like I said, there’s nothing WRONG with the 5R4, it’s just that it was
designed for much higher voltage applications, and lower current than a
5U4. Fender amps run in the mid 400s for Voltage, so there is no need for
the 5R4s higher voltage capability. At high current levels, the forward
conduction drop through a 5R4 would be high. Considerably higher than a
5AR4.

I never recommended trying to use a 5AR4 at the voltages you’d use a 5R4
at, it would be foolish to do so.

Regarding the 5R4’s ratings, my Sylvania Tube Manual says with a capacitor
input filter, it’s good for 150 ma. The 5U4 is rated at 275 ma.

Bottom line is that if you have a Fender, use a 5U4 or 5AR4, not a 5R4.