Ronsonic wrote:The Epi Valve Jr is not a Champ copy.
JiM wrote:Ronsonic wrote:The Epi Valve Jr is not a Champ copy.
Yep, not directly. But it's more-or-less a reissue of the Gibson GA5 Skylark, which itself was very close to the Champ of that time ...
If you look at the 5E1 Champ and the Valve Jr. schematics, there are not much differences :
Modding one into the other is not very difficult ...
- Attenuation resistors added after V1a on the VJ (R6 & R7)
- Negative Feedback on the Champ : 22k from HP to V1b non-decoupled cathode
- 1.5k grid resistor (R15) added on V2 for the VJ
- the power tube is a 6V6 on the Champ, EL84 on the VJ
- Power supply uses a tube rectivier and a choke on the Champ, and its voltages are a bit lower
You're right, this version is a lot more common.Ronsonic wrote:I was thinking Champ = something more like: http://www.schematicheaven.com/fenderam ... _schem.pdf
This one is the second version (which is similar to my Harley Benton GA5, when it was stock ), the link i've posted is the third and up-to-date version (easily recognisable to its black PCB). Only 3 resistors differ.Ronsonic wrote:Wait a minute, that Epi schematic is NOT what I found inside the two I've modded. Excuse me while I google a moment.
Here ya go: http://www.diycustomamps.com/images/sch ... _schem.pdf
Hmm, no, it's not that simple.TragicTravisty wrote:so could you just replace the 6l6 in say a champ with a 12ax7? and everything would work out?
gwtekman, from sewatt.com forum, wrote:Interesting little amp. PT has 250v secondary. OT is 50K ohm primary.
Looks like a scratch build could use a reverb driver transformer (typically around 25000 / 8 ) using a 16 ohm speaker?
Few other notes :
Wall voltage = 119V
Output at Power transformer 244V
+B to Output Transformer = 313V
V2B Plate = 307V
V2A P;ate = 274V
V1B Plate = 172V
V1A Plate = 170V
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