Deluxe reverb PCP to PTP with idle hum

[skepasts]

I've been trying to troubleshoot a hum in my deluxe reverb build for the past week or so with no luck. I got a deluxe reverb small parts kit from mojotone and used it to convert my DRRI to a point to point amp. It had intermittent problems and was unusable to gig with, so I figured this would be a fun project to take on. I got rid of everything from my old deluxe besides the 2 amp fuse, transformers, tubes, a couple tube sockets, and the power cable. And I'm also using a stereo footpedal cable instead of 2 RCA jacks and kept the RCA reverb input/output slots at the bottom under my turret board.

The amp works fine besides the hum, tremelo and reverb are working fine as well. I think it sounds quite a bit better than my old deluxe besides the hum of course. I know the tubes arent the issue since I used them in my original deluxe reverb and even tried tubes from another amp to make sure. The hum comes on as soon as I turn on standby (if the tubes are hot), even with all the knobs at 0 and no instrument plugged in. I still have a slight hum when pulling out all of the preamp tubes except v6, then a louder one with v6 + v1. I feel like the buzz goes away with the slight hiss I get as I turn the volume knob up to max, but it's hard to tell with the extra noise from the pot on max.

I moved the bias board to the left side of the transformer so I could fit a few extra knobs on the front where the fender logo usually is. I have it wired so the volume knobs for both channels and master are by the pilot light ( volume for normal channel - volume for tremelo - master - light) with the treble knob moved to the volume slot and mid where the treble would normally be. Could the volume knobs being this close to the transformer/far away from the original spot cause the hum? I wired the pots in the new position but haven't wired the mid knobs or master as I want to get the amp working according to the original schematic before modifying it, even if I moved the parts around. I originally used regular 18 AWG cloth wire, but am now using coax (from volume pots to v1 + v2, from volume to treble pots and on the inputs) to see if it will help with the noise.

When "chopsticking" around the amp I have a pretty loud microphonic spot at V6 on the second pin that continues to the 1M resistor and 0.001 capacitor. Could this be contributing to the hum? The parts are new from mojotone so I don't think they would be the problem. I resoldered the joint, tried to move the wire dress and even went as far as replacing the entire V6 tube socket but still have the microphonics. I've tried multiple tubes here with the same result.

I found a forum entry from someone else taking on a similar project and it seems they needed a new transformer. I'd like to see if there's anything else I could try as the tranformer worked fine in my old amp.

My grounds could also be an issue, so I'll leave them below.

Grounding:
Back near power transformer -power cable, power tubes, bias board, 2 power amp filter caps ground
Near the top of power transformer - 100 ohm center tap, ground from power transformer and ground
Pots with buss bar on back going into ground for input 2 on both channels with all board grounds and 3 preamp filter caps
Reverb pedal at jack ground, black from reverb transformer at reverb output.

I kept the same wires going to the same pins for the filament wiring (ex. Same wiring goes to pins 4+5 on all preamp tubes) with the wire from 5+4 on the preamps going to 7 on the power tubes and then 9 to 2.

This is my first build, so I'm very new to all of this. I'd really love to get rid of the buzz so I could feel comfortable using this amp for gigging/recording. Any help or troubleshooting advice is very much appreciated!

[Latole]

Which PTP amp did you build ? AB763 ?

Good pictures of the amp will help.
V6 is the Phase Inverter tube, you must not hear loud microphonic. Put new good 12AT7 tube.

[sluckey]

Could the volume knobs being this close to the transformer/far away from the original spot cause the hum?

Yes. Why did you do this? I doubt you could improve on the original control panel layout.

[Latole]

Could the volume knobs being this close to the transformer/far away from the original spot cause the hum?

Yes. Why did you do this? I doubt you could improve on the original control panel layout.

I agree.

[tubenit]

I agree with Sluckey that relocating those pots could be the issue.

PLEASE post some hi-resolution photos of the inside of the amp so we can help you more effectively.

With respect, Tubenit

[pdf64]

I've been trying to troubleshoot a hum...I'd really love to get rid of the buzz...

So is it a hum (like you don't know the words) or a buzz (like a bee, with high frequency content)?
What is its fundamental frequency, eg 60, 120Hz?

...I have it wired so the volume knobs for both channels and master are by the pilot light ( volume for normal channel - volume for tremelo - master - light)...

Such long wiring runs for such sensitive circuits really aren't a good idea. What type of master vol? It would be far better to build according to proven layouts, then try mods.

Grounding: ...Pots with buss bar on back going into ground for input 2 on both channels with all board grounds and 3 preamp filter caps...
Reverb pedal at jack ground, black from reverb transformer at reverb output.

Soldering an 0V buss wire to the back of pot cases creates multiple 0V to chassis connection points, which can confuse matters. It has no benefit over just using buss wire, and has the rather significant drawback of making pot replacement and other changes burdensome.
As things stand, you have created a possibly unique, somewhat random and complex 0V to chassis connection system.

Combining unprototyped mod layouts with the bussbar soldered to the pots may have you kinda painted into a corner.

But first things first - voltage survey, what idle plate or cathode current are the power tubes drawing?

[skepasts]

Thanks for the responses, I will post some pictures later today.

Yes its an AB763. It sounds like a 60 cycle hum.

I moved the pots as I wanted to add a mid control and master and wanted to have access to everything at the front of the amp. I haven't wired in any of the modifications yet, all I've changed so far is the placement of the volume pots to the bias supply's normal location and moved the bias supply to the left of the transformer. I have a feeling that the volume pots aren't the issue though as I still get the hum with tubes v1-v5 pulled.

I'm getting around 402-403 volts on pin 3 on the power tubes.

Would you suggest getting rid of the buss bar on the back of the pots and ground the turret board grounds to the back of the pots?

[pdf64]

An audio clip of the issue would be useful.
A 60Hz hum, together with the symptoms described, may indicate that the rectifier tube, or wiring to it, is bad, ie one plate not conducting.

[vampwizzard]

Also, for what its worth, most of the added controls ive seen on blackface amps use a cannibalized input jack with a master volume pot hole added on the rear of the amp to keep it away from the power section. Rivera mods look like this knob wise: https://www.youtube.com/watch?v=wTWq2o-nFFM

[skepasts]

Sorry for my delay, I've included some pictures and audio samples in a zip below (could not upload mp3s). I moved around a couple of the grounds to see if it would help, but I had no luck.

When I was chopsticking the volume cables, the hum would get worse when I moved the cable closer to the transformer. It looks like I may have to get a new faceplate and move the knobs back to their original spots, or at least closer to, however I thought I'd give you guys all the info first to see if there's anything I can do. I'd like to keep them where there are if possible. The master knob is in place but not wired and the mid knobs have not been installed yet.

I pulled tubes V1-V5 for the 1st clip. It starts with the standby off then switched on, repeated.

I just added V1 for the 2nd clip. It starts with standby turned on (all knobs off) - volume up to 10 then back down to around 3 (hum seems to disappear here when the volume is really high) -plug in guitar (hum increases) - treble all the way up then off - bass up all the way then set to 4 or so - playing - standby off. I play at around 25 seconds (keep this in mind as it's considerably louder than the hum) so you can hear how loud the hum is in comparison to my guitar signal. Like I said in my original post, its not incredibly loud, but enough that I know it isn't normal.

Clip 3 shows the tremelo channel. I also found some problems I thought I got rid of on this channel. The reverb is buzzing pretty bad when I turn it up and the Tremelo clicks while on (You can hear it at the beginning).  The clip goes as follows: Standby on - term Volume up then down (set at 3ish) - Volume 1 up then down (does not get rid of hum this time) - guitar cable in - treble up then down - bass up then set to 4ish - playing - turn reverb on then off - turn tremolo up /move knob - add reverb

I think I can fix the tremelo by adding a capacitor which seems like a common problem/solution, but any advice on the main hum or reverb buzz is appreciated. Let me know if you want any specific audio clips or pictures as well. Again, this is my first build so any advice is appreciated.

Because of the file type/size limitations, I uploaded the clips and pictures to Google drive here: https://drive.google.com/drive/folders/1akT8HhvfnN0tLxIlf3B44lTTsfalNy-i?usp=sharing