From cign–(at)–elios.phy.OhioU.Edu Sat Jun 24 21:03:12 CDT 1995
Article: 50174 of alt.guitar
Newsgroups: alt.guitar
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From: cign–(at)–elios.phy.OhioU.Edu (Dave Cigna)
Subject: Re: Fender Champ Problem
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References: <3sel7r$lv--(at)--ews.service.uci.edu> <3sesl9$it--(at)--irewall.ihs.com>
Date: Sat, 24 Jun 1995 20:26:23 GMT
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In article <3sesl9$it--(at)--irewall.ihs.com>,
Steven Milberger wrote:
>Try replacing the rectifier with an American made 5V4GA
>instead of a Sovtek 5Y3. A used American tube is most
>always better than the Sovtek equivalent. Weber’s book
>explains why the 5V4 is better than the 5Y3. […]

My opinion of Weber is that he’s too opinionated when it comes to
rectifier tubes. He almost universally recommends replacing whatever
rectifier happens to be in your vintage Fender with whatever tube he
happens to find with lower losses (higher resultant voltages.) This
will make most amps tighter and brighter, but the fact is many people
prefer the browner, more compressed tone of the correct tube that ol’ Leo
specified. Weber was probably refering to tweed Champs anyway,
since blackface Champs are running respectable voltages as it is and
silverface Champs are already TOO HIGH. This means that the silver ones
have a little less warmth and sweatness already and using a 5V4
rectifier will only make them colder. (Incidently, you can lower
the voltages of silver Champs to blackface levels by installing
a 10 (or more) watt, 1000 ohm power resistor between the rectifier
and the first filter cap. email me if you’d like more details.)

>
>BTW, does anyone out there know if the Champ need to be
>rebiased when changing the 6V6 tube? I didn’t see a bias
>pot so it must be fixed biased?

They’re cathode biased and I’ve never known it to be necessary to
rebias them, though you can tweek the tone a little that way.
One note is that the cathode resistor on blackface Champs is
usually underated at 1 watt. I sometimes replace them with 2 watt
metal oxide pieces. More importantly, the bypass caps on almost
all Champs are underrated at 25 volts. To make matters even worse,
the resistor is usually mounted right on top of the capacitor thus
overheating it. I recommend replacing the bypass cap with a fresh
25uF/50V unit and separating the resistor and cap as much as possible.

— Dave Cigna