Tube Amp Archive

On Fender amps, the brass plate is typically soldered to chassis near the power amp end (just to make sure). But your problem is not an issue of where the ground is located. Lou has been giving you good blind advice, but a few pics would probably do the trick. I have a camera readily available now....

Because in theory couldn't I just add a square wave oscillator and switch between the two, using an SPDT that's placed just before the pots? I don't understand the EA circuit well enough to know where to put the switch though. Or maybe I understand it so incompletely that this isn't possible?

This is about as simple as you can get: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/ietron/square7.gif It's one op amp extra to build this square wave circuit and it works like a champ. And then there is this circuit that generates a triangle and a square wave: http://www.circuitstoday.co...

This is a pretty easy trick to implement. You can pretty much steal the entire oscillator circuit from the tremulus (including the ramping circuit) and slap it onto the EA. In the GGG schematic, everything before the DC blocking cap (C4) is for the oscillator circuit and so this is what you want to...

I know it's not a tube amp, but you guys are smart! I built an EA Tremolo a while back (http://www.generalguitargadgets.com/pdf/ggg_eat_sc_improved.pdf) and want to add a "ramp up" mod to change the signal to a more sawtooth wave. It'll be controlled by a DPDT switch. The "ramp up" mod idea was take...

I know it's technically not tube amp related, but you guys have so much knowledge, I couldn't pass up an opportunity to ask. My 5 year old son has taken an interest in my pedal building. He doesn't play guitar, but I had a cool idea for a "pedal" to build for him. I have a few dozen 3mm LEDs laying ...

Alright! Vacation time kicks in this week. I'm ready to dedicate serious time to this thing. Here are some pictures. Let me know if you would like to see pictures of anything specific. I have a camera handy now. [IMG:1024:764]http://i347.photobucket.com/albums/p462/davidjnichols/IMG_5478-1.jpg[/img]...

I've never encountered the 'brass plate' grounding system. I assume the plate is connected to the chassis by virtue of bring sandwiched with the chassis at the pot shafts and input connector? I didn't see anything on the weber layout that suggests a ground wire to be soldered to the brass pate at o...

Possibly. If you have the ability to take pictures, I'd like to see the corrosion on the cap, as well as the RED/YEL termination to chassis and C13+ termination through to the brass plate. It seems like there may still be an issue with a GND connection - possibly a cold solder joint, or a loose scr...

Possibly. If you have the ability to take pictures, I'd like to see the corrosion on the cap, as well as the RED/YEL termination to chassis and C13+ termination through to the brass plate. It seems like there may still be an issue with a GND connection - possibly a cold solder joint, or a loose scr...

Progress! It looks like you've got a weak connection to GND, either at the RED/YEL chassis GND, or at the point where C13+ ties to GND. Do you have a clip lead? If so, clip one end to the solder lug where you've got the RED/YEL wire attached to chassis, and the other end to C13+. Then check your vo...

So we are down to four parts in the circuit: Power transformer bias tap (BLUE/RED; measures 47.4 VAC to GND) D1 R26 C13 Some questions: - Can you verify R26 is indeed 1K-Ohms? - Is the RED/YEL wire from the power transformer connected to chassis GND? - Using your ohmmeter on the lowest scale, what ...

Divide and conquer. Here's what I'd do next: At the pot, there is a wire that goes over to the two 220K resistors. Lift this wire at the pot, and recheck your voltage at the minus side of C13. Again, C13 is in the circuit, but one side of R28 is lifted, and we're looking for about -67V to GND. As f...

So something connected to point D is pulling its voltage toward GND. The only other things connected to D are the folliwing: R19 R20 C7 C8 Follow your wiring from C13/R27 to R19, R20, C7, and C8 to see if anything looks amiss. The only other thing that comes to mind is the possibility that C7 or C8...

Here is what I'd do next: Lift one end of R28 so that both R27 and R28 can be measured out of circuit. Measure each one individually, making sure that when you measure the pot, you have the wiper parked at the end that is tied to the wiper. R27 should measure at about 50K, and R28 should measure 27...