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Old 23rd June 2012, 11:42 AM   #911
cjkpkg is offline cjkpkg  United States
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This is the best I can do now...the wiring and placement is just temporary until I get everything sorted out...
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Old 23rd June 2012, 12:11 PM   #912
tinitus is offline tinitus  Europe
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keep power supply wires away from signal wire

amp board and supply board should shift/change place
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Old 23rd June 2012, 02:07 PM   #913
cjkpkg is offline cjkpkg  United States
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yup...rearranged to this and did two more things...
1. tried a toroid just to rule out xformer noise
2. yanked out the rca outputs from the chassis

with the toroid the hum comes on immediately and is even louder.

After I rearranged it with the EI core xformer it came on and played nicely for about a minute and then the humm came back. Thats when I tried the toroid.

So I am at a total loss here...I even threw in a pair of EL34's again to rule out the tubes...and same thing...hummmmmmmmm

I am about ready to throw in the towel on this one...
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Old 23rd June 2012, 02:08 PM   #914
cjkpkg is offline cjkpkg  United States
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forgot to attach pic...
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Old 23rd June 2012, 02:13 PM   #915
Salas is offline Salas  Greece
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Its either you got something traced totally wrong regarding the audio schematic on PCB or you get a strong oscillation, which sounds like hum if high amplitude. Maybe that is why it comes and goes. In an open loop pre with a reg you can either get it from the interaction with the reg, or with the signal run and the grid. Are there 1K grid stoppers tightly soldered to the grid pins? I suggest you hard wire it.
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Old 23rd June 2012, 02:23 PM   #916
Salas is offline Salas  Greece
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I also see wide loop area on your B+ GND reg output wires. Twist those tightly.
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Old 23rd June 2012, 02:34 PM   #917
cjkpkg is offline cjkpkg  United States
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should I try and increase the grid stopper value to 1.5K or 2K maybe?

I triple checked the board traces and they are correct...the 1K grid stoppers are very close to the pin 5 on both channels.
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Old 23rd June 2012, 02:37 PM   #918
Salas is offline Salas  Greece
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Do you have a scope?
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Old 23rd June 2012, 02:48 PM   #919
Salas is offline Salas  Greece
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If you got one, set it to AC input and check the B+ line at 5mV and 50uSec. If it ain't a horizontal line, but its a sine or a thick mess, its power line oscillation. If you have not got a scope its difficult to know. I would start by twisting B+ GND wires. Are the ''triodizing'' resistors tight for pins 3,4? Larger grid resistors I doubt they would change something.
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Old 25th June 2012, 11:31 AM   #920
cjkpkg is offline cjkpkg  United States
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And they did not...I tried 1.5K and 2.1K and same result.

I think that for the principle of the matter I will P2P this I just need to reorder some resistors. I have all the other stuff.

I cant believe that 2 different PSU's I use on 2 other amps I have are that noisy. It must be something in the layout of my PCB.
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