1969 Fender Champ Amp repair

[Steelwitch]

you know, I was thinking more about the grounding when I realized that the 15k mid resistor isn't even in here! The bass pot looks is not mounted in like the others so my guess is someone took it out of here a long time ago.. or someone at fender was having a bad day and forgot the mids resistor. just clipped in a new one and the frequency response for both treble and bass are doing exactly what they should.

[Steelwitch]

Pretty sure it left the factory like this, it doesn't look like there was ever a ground connection for the 15k

[eschertron]

Pretty sure it left the factory like this, it doesn't look like there was ever a ground connection for the 15k

You may well be correct, but the 'tone stack lift' / '5F1' mod was pretty popular.

I'd think twice before besmirching saint Leo's reputation

[Chuck H]

This:

I tested the pot already and it looks good, wiring looks ok, the 250pf coupling cap tests ok. What else should I look for? Any tricks for tracing a problem like this? Thanks!

Could someone have lifted the tone stack? Maybe a bad solder connection on one end of the 'mid' resistor to ground?

All grounds and wiring are solid.

The EQ stack has a 15K fixed resistor which sets the midrange.

I poked around at the circuit on a scope and all connections were definitely good...

If the tone stack is actually not functioning then it it is either because the tone stack ground is bad or because the circuit has been altered to bypass it.

then:

you know, I was thinking more about the grounding when I realized that the 15k mid resistor isn't even in here!

This problem was diagnosed very early on. But I'm glad it's fixed now. I just couldn't help this poke though

[Leo_Gnardo]

This problem was diagnosed very early on. But I'm glad it's fixed now. I just couldn't help this poke though

"It's what you leave out that counts!"

Well at least we haven't gone on a 700+ post endless expedition like we have with a couple folks, who I'll purposely not mention.

Slap in a 15K, or anything close to it, or a mid pot. And let's get on with life as it should be. : put smiley thing lounging under a palm tree here:

[TimmyP1955]

I just worked on a bone stock '65. The bass and treble controls both had a lot of sweep. Cathode caps were way out of wack, otherwise it was just fine.