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Post by natemeanie on Jul 18, 2021 14:08:19 GMT -7
Just wondering if I’d be ok swapping the 5y3 for a 5v4 in my RX Jr? Love how it tightens up the low end, but want to be sure I won’t do any damage before I gig with it. Thanks!
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Post by dcarver on Jul 18, 2021 14:40:16 GMT -7
I'm pretty sure you can. However, I'm no expert and I don't own an Rx Jr. Check out this video Doc did on rectifiers. He specifically addresses your question at the 10:50 mark.
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Post by Mark (Basement Enthusiast) on Jul 18, 2021 18:13:24 GMT -7
5V4 ought to be okay in a Doc-built 5AR4-designed circuit; it's pretty close to the 5AR4. (Though I wouldn't recommend going down to a 5U4 because they draw more current and could stress-out the power transformer... unless Doc says it's OK specifically on that one.)
EDIT: I have to point out that I was mistaken, thinking that the RxJr came with a 5AR4. If that were the case (like most of Doc's amps) it'd likely be fine to drop down to a 5V4. But the RxJr's stock rectifier is the 5Y3--which I would not initially recommend increasing upwardly towards a 5U4 or 5V4 without clearance from Doc.
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Post by jhen86 (jordan) on Jul 28, 2021 6:42:09 GMT -7
Been where you are. I’ve tested multiple rectifiers in my M12 and RXJR. My recollection is that the way Doc designed the RXJR, you are already at 300v on the plates with the 5y3, and the bias is set right at 12w of plate dissipation, which is there max rating, or 100% of that as some say (100% idle bias current is the traditionally quoted “safe” limit for cathode biased amps).
If I recall, I believe a 5V4 puts about 345v on the plates of the el84’s and biases them about 16w per tube of plate dissipation. Your amp will be fine. Shouldn’t hurt anything but your tubes. Expect a much shorter life cycle at those settings.
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Post by jhen86 (jordan) on Jul 28, 2021 6:46:38 GMT -7
If you REALLY want to try it and live with a bigger rectifier. I’d recommend the 5V4, 5Z4, or 5AR4. You definitely would want to replace the 125 ohm bias resistor with something in the 150-180 ohm range to cool the amp down and not cook your tubes so quick. Grab a 10 watt ohmite like the one in there.
At the end of the day, you’ll have more power and drive, which to me, neither of those are lacking in the stock RX...so I’d just leave it alone probably. But I get your curiousity and need to experiment. Support you in that.
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Post by Mark (Basement Enthusiast) on Jul 28, 2021 8:53:24 GMT -7
OH.. Jordan's right, and I forgot earlier that the RxJr is spec'ed for a 5Y3. (It'd likely be OK to go down from a 5AR4 to a 5V4 in an amp designed for a 5AR4. But going up from the 5Y3 to a 5V4 in an amp designed for a 5Y3? Maybe not, definitely ask Doc.)
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