5E3 Deluxe Zap/Hum Noise on Standby & Low Output

[jonyoungyi]

Hi, just finished a very ambitious 5E3 build, but noticed these two issues:

1. When the standby switch is on (No B+), I'm getting a zapping/hum type of sound. It kind of also sounds like farting out, but with a hum-like pitch. When I turn standby off (B+ Provided to 1st filter cap, etc), the weird sound goes away. I should mention:

-----a. My PT isn't flush mounted to the chassis (didn't want to cut a square, so mounted it on standoffs).
-----b. I didn't install the artificial 100R CT, as my PT already had a CT for the 6.3v heaters (That should be fine right? I already have a "real" CT).


2. I'm getting very very low output. Master volume (replaced 1M PI grid leak with 1MA pot), normal volume, and tone are all maxed out, but I am getting little tiny guitar signal, almost inaudible, unless I put my ear to the speaker (12" speaker).

-----a. Do you think my input signal has a cold joint or is somehow bleeding into ground?

Anyone ever experience that first one? That first one is the first time I've had the issue from the 5 amps I've built thus far.

Any and all help is much appreciated, thank you!

[sluckey]

When the standby switch is on (No B+), I'm getting a zapping/hum type of sound.

Is the sound coming from the speaker or chassis? How do you have the standby switch connected?

I'm getting very very low output.

Could be almost anything.

We need tube voltages and filter cap voltages. Your schematic and layout will be very helpful. Hi-rez pics of the inside of the amp are also helpful.

[jonyoungyi]

Hey Sluckey!

When I get home I was going to disconnect the speaker when in standby to see if it goes away. But, I can't imagine the PT, itself, making that kind of noise. I have the standby switch connecting the rectifier to the 1st Filter cap. I used to have a switch pop resistor between the switch terminals to let a small amount of current through, but removed it to take that out of the "equation". Noise still persisted after removing.

I'll get voltage readings and post them up tonight. From what I remember my filter cap voltages were a bit higher than the recommended voltages (https://robrobinette.com/5e3_Modifications.htm#Standard_5E3_DC_Voltages). I'd say maybe 10 to 15v's higher.

I'm using a layout/schematic from Hoffman's 5E3, but modified it with a bunch of mods from Robinette's page.

I've attached a Hoffman 5E3 layout that I edited with the mods. Kind of confusing I know, but I've triple checked all my connections for the mods, especially the split TONE/VOLUME controls, the master volume, and the Fixed/Cathode bias switch+50v bias

Thanks for the reply Sluckey!

[jonyoungyi]

Turns out the loud hum was coming from the speakers. Here's why:

I wired the OT Transformers RED wire directly to pin 8 of the rectifier tube, as opposed to wiring it on the B+ or B+ side of the standby... My mistake, my mistake.

Also, I noticed cold joints on my FX loop which were causing the low output volume...


5 Amps in and still a rookie!

Now I have an issue with crackling, unpleasant distortion when hitting chords. Also noticed that the 5e3 is not very loud. Cranked GAIN and MASTER volume, but still reasonable volume. Like, not enough volume to disturb my apt neighbor.

I've already lowered the .1uf caps to .022uf and modified one of the channels to have a .68uf electrolytic & .0047uf cap. Weird that it's still distorting, but I guess it's not the kind of distortion you would get when there's too much bass, so could be different.

[jonyoungyi]

In case anyone has the same issue, here's what I did to fix my 5e3's low output and blocking distortion:

Turns out my FX loop and TC pedal's (I mounted a TC Hall of Fame & TC Ditto inside the enclosure) connections weren't good. More specifically the lead going from FX Loop RETURN to the TC Ditto (I wired FX Send -> FX Return -> TC Hall of Fame -> TC Ditto). After applying a bit more solder and pushing the wire in the through hole it wasn't causing blocking distortion.

Now for the low output. I used the Pre PI master volume mod from robinette's website. Used a 1MA pot and shielded wire for all 3 lugs. Here's where I messed up. I soldered the 3 shielded wires' grounds to the back of the pot. First issue, it's best to solder the shielded wire ground from the signal's "Sending End", and not where it's "Ending" or terminated (if that makes sense). Second issue, I applied way too much heat to the back of the pot so it went bad!

After replacing the pot with a new one and only shielding Lug 2's shielded wire to the back of the pot, there's so much volume now!

If anything, the 5e3 is super clean... Like, it's almost an issue now haha I haven't had a chance to play it on max settings, but when I max the volume and turn down the master and hit a chord, it doesn't breakup all that much haha Strange, but it's kind of what I was going for. Headroom.

Anyway, I hope this helps someone, as so many of you have helped me with all 6 of my amps.

Until the next one, keep at it!

[hokenpoke]

I wired the OT Transformers RED wire directly to pin 8 of the rectifier tube, as opposed to wiring it on the B+ or B+ side of the standby...

If anything, the 5e3 is super clean... Like, it's almost an issue now haha I haven't had a chance to play it on max settings, but when I max the volume and turn down the master and hit a chord, it doesn't breakup all that much haha Strange, but it's kind of what I was going for. Headroom.

Anyway, I hope this helps someone, as so many of you have helped me with all 6 of my amps.

So this was very helpful to me - I had the same buzzing on standby from my new 5e3 build and (duh) it turns out I had the OT center tap on the wrong side of the switch.


I have also implemented the Rob R pre-PI master and I, too, have noticed that this thing is running on the clean side even with all the knobs Nigeled.  This is a very tame beast compared to the other 5e3s I have had experience with.  Also, the Master seems to need a linear taper pot rather than audio taper - Almost all of the effect is at the very bottom of the range though it does change the character of the crunch as you continue to turn it up.  I think I will experiment with a 12AX7 in V1 and see if I get some earlier breakup.


Have you experimented further with anything on your amp?

[jonyoungyi]

Hey hokenpoke,

Yeah, I added a lot of mods from Rob's site. Here's some that I can remember:

Edge Mod
Voicing Mod
Balance PI Mod
3-way Feedback
Master Volume
Switched Bias
Adjustable Fixed Bias
Standby Pop Reduction
Dual Channel Mod (Both Channels at once)

I think that's all of them, but I'm sure I forgot a few!