New DR build, suggestions

[sonofmickel]

Well, the last build failed on many levels, so I am gutting the amp and trying again using good parts.

The original was a Weber 6a20HP that was shipped with an undersized PT (150ma but designated for 6l6).
I hope the PT is still good, it good too hot to touch in 2012/13 when I first built the amp, that was with 6l6gc in there.

I am still using the original Weber Iron: PT, OT, Reverb Transformer and choke.
They all seem a little cheap but the amp originally did sound like the best thing I had ever had in my possession...

Changing out the eyelet board for the Hoffman AB763 Reverb Eyelet board, keeping the Weber Capacitor wax board and bias wax board.
Changed to all Belton sockets, Belton RCA jacks for Reverb and Tremolo(Vibrato) jacks and better input and speaker jacks.
New Mallory/type coupling caps and better resistors.

I would like suggestion and or tips, if I am straying off course.
I wired the heaters lay-down style.
Is the lead dress looking successful?

Original chaos!

[sonofmickel]

Heaters

[sonofmickel]

Bias test points, stby/power switch, center tap grounds.
Anything look out of spec?

[sonofmickel]

Power tube screens 470ohm vs 1k 5w?
Only 6v6s going in this amp.

[BrownIsound]

I prefer 470 for fenders, but if you will be cranking it a lot and/or with pedals, 1k might work better.

[sonofmickel]

Yes, pedals, modeller in front.
1k 5watt cement installed.

Is there a preferred way to install the belton RCA Jack's?

Reverb pot, Linear vs Audio taper?

[BrownIsound]

I think linear is stock, but audio taper may give you better control of the lower part of the reverb ( never tried it myself).

[lonote]

If you have an extra hole on the back panel, preferably towards the input end, you might like having a dwell control. It is as straight forward as replacing the 1M resistor to ground on the reverb signal lead (just after the connection that feeds the reverb driver grid) with a 1M pot. Pot resistance end-to-end goes to ground, wiper to the tube grid.

It opens up the variety of reverb settings as you can work the input of the reverb circuit against the output. I have added it to most of my projects.



A Sluckey drawing attached.

SluckeyDwell.png

[burchyk]

I'd change up the normal channel to have more tonal variety between the 2. Lately been enjoying 2uF cathode bypass cap on the first gain stage, which seems to work better with dirt boxes, especially a fuzz face.

[sonofmickel]

Amp is built...hum problem!
All tubes pulled but, power and PI, produces 60 hz hum.
Pull PI = no hum.

Volume knob does not increase or decrease hum(no tubes installed in preamp anyway).

With all tubes installed the amp works(vibrato and reverb work fine) but has the same 60hz hum, volume knob does not increase or decrease hum.

[sonofmickel]

Hum fixed:
Somehow a bad grid connection on V1B, pin 7 causes excessive hum.
I reflowed solder on all suspect joints, some in the power section, PI and a few preamp tubes.
Amp seems to sound great.
Still have the hum at whisper levels...I suspect it is a grounding issue.
I will install bus bar for the preamp section and investigate separating the filter caps of the preamps and reverb tubes.

Suggestions welcomed for separating the filters.

Amp tone is pretty good, maybe the dwell knob will make reverb "better"
I have space between the RCA jacks and Output jacks, could be a good spot.

Input jacks still need to be rewired/cleaned up.

I definitely need to change the bulb socket, it is intermittent and...I just have to replace it, so close to grounding out/scary part.

[sonofmickel]

Nearly done with it.
I installed a Mid pot on the normal channel, not sure if it will stay.
May need to do more to that channel if it stays, 2k, 2.7k, .68uf. Don't know yet.

Problem:
Symptom 1: Very light hum in the background, it goes away when the chassis is touched, nothing plugged in.
Symptom 2: Noisefloor/hum increases more on Vibrato channel when turning up the volume knob, nothing plugged in. Normal channel does not increase the Hum/noise floor.

Bad electrolytic?
Bad ground on reverb/vibrato?
Bad ground on RCA jacks?

More research needed.

[burchyk]

Symptom 1 feels a bit counter-intuitive the way you put it. My hunch is that it might rather be that something is not shielded or grounded properly, and when you're "touching chassis" it is rather that you're grounding yourself, which tends to reduce the interference on the audio circuitry.

[sonofmickel]

thanks, it "may" be my grounding method. It's my least favorite and probably most important thing to do!
I will redo my ground with twisted bus wire and make sure it has solid solder joints.