Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Bottlehead Forum ]

---

[ Alert Moderator ]

---

Re: What if you reconsider...

Posted by Jim Carlon on September 24, 2002 at 07:51:38

In Reply to: What if you reconsider... posted by csown on September 23, 2002 at 15:03:15:

Yikes! The cap and resistor mentioned in my post should be connected in SERIES across the switch contacts!

For what its worth, in 6 years of servicing Fender and other guitar amps, I have never seen a 'standby' switch failure, other than cases of actual physical damage. This was usually damage to the toggle/handle. As far as failure due to arcing, I simply have not seen it happen, and indeed, this is on equipment that has been in service for 30-40+ years.

While Fender did not use a snubber across the contacts, the switch was in a rather good spot in the B+ line, after the first cap and before the choke, in a CLCRCRC filter. I imagine that the L and Rs relieved a good deal of inrush stress to the switch. As I have mentioned previously, B+ was typically in the range of 465-485 Vdc at this point, and the switch was a common Carling SPST toggle rated at 250 Vac, 7A. A similar switch was used for AC mains.

A great deal has been written about cathode stripping and cathode poisoning over the years, but I must say that I have really never seen wany empirical data, ie: stripping reduces useful life by x hours, poisoning causes failure in y hours, etc. As far as guitar amps are concerned, I don't think that this was even considered---remember, this was called a 'Standby' switch, and its intended purpose was to provide a quiet-but-warmed-up state for times when the musician was not playing. As such, the amp may have been left in this state for a 20 minute break, or for an hour before the show.

Personally, in a new design, I very much like the idea of using a damper diode tube, ala Bluesmaster, for a simple, fool-proof slow turn-on. Nothing to remember for the casual user, no mechanical or SS devices to fail, and Svetlana still makes one.

If it is an existing piece, I still think a good quality switch is the simplest solution.

Jim

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

Parts Connexion

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

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

---