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No offense Joe, we love ya, but I'm building one and I need a drawing with no mistakes. I don't trust the 4M treble pots, or the 270K going from the bass middle wiper to ground. Anyone?
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It's weird, because it WAS working fine..... -
EDIT: forget what I wrote before.
Here's an Ampeg scan:
The original image is somewhat unreadable, the treble pot label *looks* similar to "4M" but of course it's 1M , like on all other Ampegs, (and even if it actually said 4M, I'd consider it a Factory Typo, I don't hold Religious Awe and Deference for Factory data by any means).
And it does show the infamous 270K resistors to ground.
Its net effect woud be to reduce a little the max bass boost available, nothing else.
Try with and without .... and choose by yourself .Last edited by J M Fahey; 02-05-2015, 11:16 AM.Juan Manuel Fahey -
Ampeg was about as bad as Fender with adding in factory mods... the difference is, Ampeg (at least at first) would ink the changes in on the included schematic. I kept wondering why the online GS12-R Reverberocket II schems didn't have the heater elevation that mine had on the schematic. But I had to look VERY closely to realize someone added it after the fact, and it was nearly indistinguishable from the printed ink. At least after 35 years...
Maybe someone DID put a 4Meg Treble pot in it at the factory and changed it back. Who knows? And that was how I learned about elevating the heaters in amps - I freaked out when I measured 30V on my heaters!
B15: Every time I see that schematic, I marvel that such a simple decrepit old out-of-date-even-at-the-time piece of laughable technology could make such glorious sounds and be used on countless popular and critically acclaimed records. I mean, cathode bias and a paraphase? That'll NEVER work for bass! >:O
Sorry, was inspired by Juan's post in the West thread...
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -Comment
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Thanks guys, looks like Joe's drawings are pretty faithful to this scan. Sorry to be so quick on you Joe! Can someone explain the "K" on the heater balance center leg and cathodes of the outputs? Does this connect them? And if so, why?It's weird, because it WAS working fine.....Comment
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Yes. That means that they are electrically connected. The power tube cathode voltage is thus used to DC elevate the heater supply.Originally posted by Randall View PostComment
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Got it, thanks!It's weird, because it WAS working fine.....Comment
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