English Channel Problem

[ildar]

Finally got my EC finished, FETs biased properly, and it sounds great...except...
The bass pot is acting as a volume, and the cut pot seemingly has no effect. I used the old version PCB layout from ROG.
I'm away from my workbench now, so I can't verify any wiring or voltages, but if anyone else has run into this, I'd appreciate their input.

[RDV]

Check your wiring around the tonestack. The bass pot should not be doing this, the treble pot would have more of this effect normally as it feeds the rest of the circuit.

The cut control as it's configured does very little, a larger cap will give you more control there, though I'm at work and can't remember what value I used.

I'm going to work on mine some more once I get some bifocals so I can see the parts again. I get a headache these days trying to read part values.

I plan on appling some of the same mods I used on my Dr. Boogie involving "Miller Capacitance".

RDV

[ildar]

I'm going to work on mine some more once I get some bifocals so I can see the parts again. I get a headache these days trying to read part values.

RDV

I feel your pain.  I was called middle-aged for the 1st time last Friday. 

I did have the wiring for the bass and treble pot flip-flopped, but should it still act as a volume control? When the pot is fully counter-clockwise, there is no signal.

[dano12]

Here's a wiring diagram I drew up for the EC for a friend. I'm not sure if it is the same ROG board that you used, but it may be of some help in diagnosing your problem. Also, remember that the Cut knob works in reverse of normal pot rotation, just like the original Vox.

[awilson40]

Mine worked fine the first time...However, the Treble Cut, while does have effect,
operates backwards from what is explained. Turning the control Clockwise ADDS treble
instead of cuts it. I dbl checked all wiring and its correct. No big deal to me.
And I feel your 'aging eyes' pain....
Dudes this is a life saver, get one now !!!

http://www.radioshack.com/product/index.jsp?productId=2104639&cp=&origkw=magnifying&kw=magnifying&parentPage=search

[ildar]

All in all, I'm more concerned about the volume oddity with the treble control than any anomaly with the cut pot. I'll work on that later, but I wonder if the volume deal is interrelated.
To dano12-thanks for the layout, but I used an older PCB and layout that had been verified, but is no longer available online. It follows the perf layout on the ROG site pretty closely, and I did compare the newer pcb with mine, and everything seems to be correct, or at least similar between the two.

[ildar]

Well, I'm calling this a successful build. I went over everything, and it all checks out. The treble still kills the volume, so I just keep it dimed (maybe that's why there's a treble cut to begin with?). I replaced the 4n7/250k pot configuration with 0.1uf/10k and it works nicely, with good parameter control. I then rebiased all the FETs, but underbiased (?) Q5 at 3.75v to clear up some slight splatiness. Tomorrow it gets boxed up and goes into the rotation.