Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Vintage Asylum ]

---

[ Alert Moderator ]

---

RE: a question about what exactly was the problem

Posted by Russ57 (A) on February 28, 2015 at 15:52:54

In Reply to: Help needed: 4uF PIO capacitor (Hunts) sought, or PIO replacements? posted by jusbe on February 26, 2015 at 20:00:26:

I see some mention of runaway voltages, that the 4uF hunt capacitors were bad, maybe that a couple of EL34's were found to be the problem in the end. Hard to make heads/tails of what the original problem/symptom was. Could be I didn't read closely enough.

If you look over the parts list you will see that not all the capacitors in the power supply have the same voltage rating. If we assume all tubes work then the capacitors (going from output transformers, to ecc83, to ef86) will see decreasing voltages. But if, and this is a huge if, a tube (or tubes) fail to draw the expected current then voltages on some caps would be the same and therefore well above some of their ratings. If you are going to replace any of these caps I strongly encourage having a high enough voltage rating on all of them to withstand the maximum possible voltage. That would be 1.4 times the AC voltage the power transfomer delivers to the GZ34 plates.

I am hard pressed to think of any possible way for bad power supply caps to create an over voltage situation. They would create low voltage due to being leaky.....or excessive ripple voltage due to end of life aging (which typically cause hum out of the speakers). Over voltage (in the DC power supply) is almost always related to a lack of current draw. Sometimes tubes get weak. Sometimes they make poor contact in their tube sockets.

If the coupling caps to the EL34's leaked (C7 and C8) then the EL34's would draw too much current and DC voltages would be too low....at least for as long as the EL34's continued to work at normal values (which might only be seconds if C7,8 are really leaky).

There are a million ways for you to make your amp better. To do nothing more than replace all the parts with high end ones would be a mistake IMHO. In short take your time. Try to learn enough to understand pros and cons as you seek advice from those you "think" you can trust. The internet is very much a double edged sword in that regard. When in doubt I look first to proven audio designers. Paul Joppa is one such man still posting on audio asylum. IMHO taking advice from those that stand to profit (ones that sell parts/services) is akin to trusting the used car salesman's advice on which car is best.

Also give thought to how important the "original state" of the amp is to you. I would not think it had collectors value but I don't know. Moving to a larger chassis and making some circuit/parts changes could make a world of difference.

This post is made possible by the generous support of people like you and our sponsors:

Schiit Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---