My tone stack is not completely working

[mpayne]

I’ve been tinkering with my fist build for a while now and for the most part it works well and sounds good, but my tone stack is not working.  The treble works fine but the mid and bass have no effect.  When I turn the mid or bass all the way in both directions the audio does not change at all.  There is no change in tone, volume, no pops, no clicks.   I’ve checked all my connections and measured the impedances and everything seems to be hooked up correctly.   I’ve attached the schematics.  Anyone have any ideas what the problem might be?  Overall the amp sounds good, but there is not much bass to the sound.

Thanks for your help,
Mike

[sluckey]

Looks like a Marshall. Almost got to be a wiring error or wrong value component(s). Keep looking. If you can post some hi rez pics, we can help you look.

[jjasilli]

Yes.  Print-out a copy of your schematic.  Physically trace each connection in the tonestack inside the amp, including the ground connections.  As you confirm each physical connection, mark over it on the schematic with a broad yellow Sharpie.

[stingray_65]

Yes.  Print-out a copy of your schematic.  Physically trace each connection in the tonestack inside the amp, including the ground connections.  As you confirm each physical connection, mark over it on the schematic with a broad yellow Sharpie.

Man I hate wiring tone pots.

I think my first build (5E3) was the only one I got right first time,

Trace it, go away and trace it again.  I've also confused myself a few times flipping a pot around in my head and wiring it as I'm facing it.

can you post a good hi res pic of that area? sometimes a second pair of eyes can spot an issue


Ray

[chocopower]

Man I hate wiring tone pots.
I think my first build (5E3) was the only one I got right first time...

I´m with you. My 99% of volumen pots works backwards the first time...

[mpayne]

Thanks for the replies.  I did a circuit board, in hopes that it would keep me from messing up the wiring.  Fat chance.  I've attached a PDF of my layout.  I'll keep digging into the problem.  Let me know if you see any problems.

Thanks,
Mike

[jjasilli]

Devil's advocate:  Lot's of people report that the Marshal tonestack "doesn't do anything".  What guitar are you playing through the amp?  Do other players agree with your assessment?

[VMS]

From layout: It looks like there's a connection missing between C15 and R25.

[Geezer]

From layout: It looks like there's a connection missing between C15 and R25.

That would do it...better double check that trace!

[mpayne]

Wow, that was fast.  I totally missed C15 not connected to R25.  Thanks, that was the problem.  The amp sounds much better .   I've had a lot of fun building this amp and I could not have done it with out the help from the great people on this forum.  Thanks a million!

[VMS]

De nada!

That is pretty impressive layout for a first build. Any gut shots?

[mpayne]

Thanks.  What do you mean by gut shots?

[Willabe]

He means pictures of the inside of the amp. Like lookin under the hood of your buddies newly finished hot rod. Show it off, we all learn from each other studying each others work.

Glad you fixed it.


             Brad        

[plexi50]

I took a look at the Layout and it wacked my eyes out. I cant see the dark text

[mpayne]

Here are some pics of my build.  I’m defiantly taking notes on things I would do different on my next build.  I think soldering the wires from the transformers, choke and pots directly to the PCB was a bad idea.  It makes it hard to work on and the shields around the wires just melt under the heat from the iron.   I would make have everything plug/unplug from the PCB next time.