5E3 control problems

[Doc Stitches]

input closest to volume ... ( Channel 1 ? ) sounds good up to 5 then very distorted,

bass control causes very loud hum as soon as you turn it up past 0, treble control is OK

input farthest from volume ( Channel 2 ? ) has very loud hum on any number,

bass seems to be working as a volume control, treble only works when bass is turned up ???

Magnetic Components PT and OT

Doc

[Gtr_tech]

This is a build? Original Fender?

Anyway....check the heater setup. If its wired with one side to gnd and no center tap you need to cut out the gnd wire and gnd reference the heaters with a 100 ohm resistor from each side of the winding to gnd. That will quiet heater related hum.

Other than that....you could have a bad grounding setup...IE several different ground points on the chassis causing ground loops. Its best to use a single ground point and bring everything back there. And keep the input jack ground off the chassis....

[Wittgenstein]

A normal 5E3 only has two volumes (one for each channel) and a tone knob (one for both). Did you include a fender Bassman style tone stack? Did you add another preamp stage? More information including a schematic and pics would be helpful.

[Chuck H]

There is a miswire in there. Keep looking, it's there, you'll find it. And believe me, I do know what it's like to have looked something over again and again without finding a miswire only to troubleshoot the problem, narrow it down and eventually find a miswire. Even when you swear it's not wired wrong because you've looked it over soooo carefully. Keep looking. There is a miswire.

[Doc Stitches]

Good advice Chuck............been there/done that...............I just found one of the normal input wires was not soldered on lug
Progress is time consuming but educational.
Still having issues but will post pictures tomorrow.
Doc

[Doc Stitches]

You are right Wittgenstein.......2 volumes and one tone.........No other mods
Fender Deluxe schem/layout
Here are some photos

[Wittgenstein]

Nice work. Looks like there are some wires that you could shorten, but much cleaner than my first build. It looks like your PT only has a center tap off the B+ (red/orange wire) and not one for the heaters (usually green/yellow wire). I ran into this on a recent build of mine and adding an artificial center tap made a huge difference in reducing hum. I noticed that I was getting capacitive coupling through the transformer when trying to measure the 6.3 Volts AC off the lamp, which caused strange readings (60+ Volts).

I also noticed that this only has 2 inputs vs the normal 4 inputs, which is fine. But I am confused as to why there is still all four 68K resistors going to the input jacks. I am by no means an expert, so please take this with a grain of salt, but it looks like something fishy is going on there. Good luck and I hope this helps.

[hack]

Solder your 100 ohm resistors - one leg on each pin of the pilot light, then twist the free ends of resistors to make a V. Solder a wire to that pointy end of the V.

Solder the other end of that wire to pin 8 of either power tube (they're connected).

Putting 17 volts or so DC on that heater circuit will make the amp quieter than if it had a heater center tap.

Thanks to Steve C

[hack]

Inputs look wrong

If those are Switchcraft or neutrik jacks, center lug is the switch, ground is obvious and tip is the other one. Test continuity with a meter to be sure. Put a piece of cardboard under the switch (shunt to ground) to test with meter.

Switch (center lug) should be wired to ground lug. 1M resistor should have one end soldered to ground lug and the other end to the tip lug. solder a wire from the tip lug to one of the 68K resistors. Do each jack this way.

[Wittgenstein]

If those are Switchcraft or neutrik jacks, center lug is the switch, ground is obvious and tip is the other one. Test continuity with a meter to be sure. Put a piece of cardboard under the switch (shunt to ground) to test with meter.
Switch (center lug) should be wired to ground lug. 1M resistor should have one end soldered to ground lug and the other end to the tip lug. solder a wire from the tip lug to one of the 68K resistors. Do each jack this way.

From el34world.com (http://www.el34world.com/charts/CommonHookups.htm)



The grids (pin 2 & 7) of the 12AY7 (V1) run to turrets on the circuit board, through a 68K resistor to the tip of the input jack. Normally a 5E3 has 4 inputs for hi/lo jacks on each channel. Since your amp only has 2 inputs (one for each channel) you will not have hi/lo jacks, and more importantly you should only have a single 68K resistor coming off each grid to the tip (see attachment for Single input jack). If you choose, you can opt for different value resistors on the two channels to make one higher or lower, but that is up to you.

[Doc Stitches]

Update...........................all is good with the 5E3 build. Great sound with almost no hum.
What I had was input jack issues.
I have 2 inputs not 4......well guess what....I had 2 yellow wires from each pair of 68Ks on the board going to each jack and I had no 1 meg resistor on either jack.
I disconnected 1 yellow wire on each jack and this Deluxe sounds amazing.
Thank you all very much and HAPPY HOLIDAYS
DOC

[Wittgenstein]

Glad to hear it Doc. Congrats on your new "working" build! If you're feeling really ambitious you can add the virtual center tap mentioned earlier to reduce the hum even further and measure the voltages throughout the amp to see how she's running. I know that mine is running a bit hot. Nothing that should hurt it, but a bit hotter than the 340-370VDC shown on Fenders schematic.

[Doc Stitches]

Virtual center tap........If that's the 2 100ohm resistors, pilot light, "Y" twist, to pin 8 of power tube that hack described, I did that , too.............forgot to mention it in last post.

What about my grounding wires ( brown ) ?.... Is this the best ?
Doc