Hoping for input....

[Willabe]

If you are using switchcraft jacks then you don't need to run a separate ground wire as their already grounded to the chassis by their sleeve. Adding a separate ground wire by definition is a ground loop. You should try disconnecting any separate/extra ground wires from the jacks.


             Brad     

[tylerrussell]

It's probably the tube then, unless you have a poor ground connection in the V1 circuit.

Tyler, you tried a 12BH7 and a 12AX7, do you have other  tubes to try?

I suspect ground problem.  especially since both triodes share the same cathode resistor and bypass cap...

find the ground turret for the 820ohm R and the 25uf cap.  call it turret "A".  disconnect the ground wire to "A".,  take a jumper wire (hookup wire with two alligator clips if you have) connect to "A"  and connect the other side to the (-) negative ground side of the 16uf filter caps.  (you mentioned 3ohm to ground for some ground connections, it wasn't clear to me if that was 0ohm or 3ohm)...

I believe the board will have to be pulled. I checked with a beeper on the meter from chassis to the interconnected turrets on the neg side and do not have continuity at the 1.5k/25uf; but have continuity at the 16uf's, 820/25uf, and 220k's. I believe there should be continuity at the 1.5k/25uf. It'll be a while!

If you can easily disconnect the ground wire to "A" (under the board?), its still can be a valid test to do the above jumper wire test from "A" the (-) turret of the filter caps. 

this could be a cold solder joint somewhere.   If not on the ground circuit, then on the B+ side, (grid is ruled out, what else is left?  tube, ground, B+).

[tylerrussell]

If you are using switchcraft jacks then you don't need to run a separate ground wire as their already grounded to the chassis by their sleeve. Adding a separate ground wire by definition is a ground loop. You should try disconnecting any separate/extra ground wires from the jacks.


             Brad     

This will be easier to try before removing the board.

[Ed_Chambley]

Check your 100ohm Artificial CT resistors.  They have given me much problems recently.

[sluckey]

If you are using switchcraft jacks then you don't need to run a separate ground wire as their already grounded to the chassis by their sleeve. Adding a separate ground wire by definition is a ground loop. You should try disconnecting any separate/extra ground wires from the jacks.


             Brad     

This will be easier to try before removing the board.

You don't need to do this. You've already eliminated the jacks and tube grids as the source of hum when you grounded pins 2 and 7.

I believe the board will have to be pulled. I checked with a beeper on the meter from chassis to the interconnected turrets on the neg side and do not have continuity at the 1.5k/25uf; but have continuity at the 16uf's, 820/25uf, and 220k's. I believe there should be continuity at the 1.5k/25uf. It'll be a while!

You may be missing the underboard jumper. You don't need to pull the board to check this. Just put a gator clip jumper between chassis and the negative side of the 1.5k/25µF. If this cures the hum you can put a jumper on top of the board. See pic...

[tylerrussell]

I lifted the board and re-soldered the bottom of the turret that connected the negative side of the 1.5k/25uf. Have that ground connection now. Also pulled the red/yellow PT wire off the bolt and soldered it to the chassis. Unfortunately..............Hummmm. I know I'm a true newbie, and I cannot thank you guys enough for all the thought, expertise, and input. Something is misconstruyoulated (new word) somewhere.... surely related to my ineptitude. Looked for loose wire hairs, cleaned tube pins, sockets, tried several 12AX7's from another working amp, cables; even tried a 12AT7....no difference. I'll keep looking.... have all avenues that were suggested been satisfied? Jeeeezus......at 62 years old-----this is very trying!

[Ed_Chambley]

Check the 100ohm artificial center tap resistors.  It is easy to do and I have had noise issues from them quite a few times.  Psyco mentioned it to me once while I was chasing noise on a Princeton Reverb and I doubted it, but that was the problem.  The very next week I had another Princeton with the same problem.

I do not know how it happens, but I think it could happen if you touch your probe to the plate of the power tubes and archs to the heater wire.  Not sure about this so someone correct me if I am wrong.

Either way, checking them is easier than making a peanut butter sandwich.

[tylerrussell]

Check the 100ohm artificial center tap resistors.  It is easy to do and I have had noise issues from them quite a few times.  Psyco mentioned it to me once while I was chasing noise on a Princeton Reverb and I doubted it, but that was the problem.  The very next week I had another Princeton with the same problem.

I do not know how it happens, but I think it could happen if you touch your probe to the plate of the power tubes and archs to the heater wire.  Not sure about this so someone correct me if I am wrong.

Either way, checking them is easier than making a peanut butter sandwich.

If we are speaking of the two 100 ohm resistors from the pilot light terminals to ground, they check out OK.

[sluckey]

Let me ask this... Can you even get a guitar signal thru the amp or is the hum so overpowering that it makes it impossible to play guitar thru the amp?

[tylerrussell]

I'm getting all kinds of signal through this thing. It's much louder than expected. Sounds very good. Tone control has a lot of range. Going through a8 ohm  60 watt 12". Something a little less efficient might be nicer, though. If I didn't know, I'd say if was 30 watts. But it's apparently not. Couldn't mic this amp due to the hum, though.

[Willabe]

at 62 years old-----this is very trying!

Hang in there Tyler, you will figure it out!


            Brad    

[tylerrussell]

Ya' know I think it would be easier to build another one and get lucky than it is trying to figure this out! I'll keep reading and searching.

[Willabe]

Ya' know I think it would be easier to build another one and get lucky than it is trying to figure this out! I'll keep reading and searching.

                Yeah it might feel like that now but you'll find it.

Sometimes it's best to step away from it for a little while, clear your head and go back in.


            Brad     

[tylerrussell]

Please accept a big "Thank you". You all got thing going. I found a second Triode layout that had a different grounding scheme. Followed that and the Huuuummmm id GONE. I'll attach the two different layouts. There's a slight buzz when it's dimed~a non issue. Thank you all again!

[Willabe]

Great!

Do you understand the difference between the 2 grounding schemes?

(Our host Doug basically does the same thing.)


                 Brad     

[tylerrussell]

Great!

Do you understand the difference between the 2 grounding schemes?

(Our host Doug basically does the same thing.)


                 Brad     

No, I don't. But I will work on it!