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Old 20th May 2010, 08:59 PM   #1
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Default First amp build... help please!

So I finally finished my guitar amp. There are numerous problems!

1) there is an insane amount of 60 Hz hum

2) the output is VERY VERY low, barely audible, less loud than the 60 Hz hum

3) the first preamp tube socket is extremely loose. it barely keeps the tube in when the amp is upside down. The socket is this one: Parts-Express.com:9-Pin Tube Socket Gold Plated Ceramic 12AX7 Type w/Bracket | tube socket chassis pc mount 8pin 9pin 4pin 7pin ceramic new sensor newtube07

I think the hum is because my star ground is kind of close to the heater supply. The output is also close to heater supply wires. Im not sure if I can even salvage this chassis / build.

I'll try to get pictures up!
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Old 20th May 2010, 09:33 PM   #2
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Here are the images of my poorly crafted amp
Attached Images
File Type: jpg leftside.jpg (122.5 KB, 362 views)
File Type: jpg rightside2.jpg (114.4 KB, 332 views)
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Old 20th May 2010, 09:43 PM   #3
llwhtt is offline llwhtt  United States
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Schematic please.

Craig
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Old 20th May 2010, 09:53 PM   #4
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if the box is painted, did you make sure to make ground contact to bear metal?
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Old 20th May 2010, 09:54 PM   #5
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Quote:
Originally Posted by dosilegecko View Post
3) the first preamp tube socket is extremely loose. it barely keeps the tube in when the amp is upside down.
Until you source a socket that works, all bets are off!!
Buy another socket..
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Old 20th May 2010, 11:10 PM   #6
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schematic:
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File Type: gif minicat2.gif (70.9 KB, 308 views)
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Old 20th May 2010, 11:44 PM   #7
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I just ordered a new socket, and the chassis is painted, but I sanded a spot and soldered the ground from the wall there, you can see the green wire in my pictures coming from the power socket. The star ground connected to the chassis via a screw. Its the thing with about 10 brown wires going into it.

I really think its because the sockets bad, and the heater wires are literally right next to my star ground... bad layout on my part.
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Old 20th May 2010, 11:58 PM   #8
llwhtt is offline llwhtt  United States
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Looks like you have the two sections of V1 tied together in parallel but incorrectly. Pin 1 should be tied to Pin 6, 2 to 7, 3 to 8; it looks like 1 to 8, 2 to 7 and 3 to 6, am I right? I don't think that will work very well. Since you are replacing V1 socket no biggie but the tube might have been ruined. Check all other sockets for correct wiring while you are at it, we've all been there done that.

Craig

Last edited by llwhtt; 21st May 2010 at 12:00 AM. Reason: forgot something
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Old 21st May 2010, 12:33 AM   #9
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GOOD SPOT! Wow, I wonder what I was thinking. Wait, I know! It was 3:30 AM! Let me fix that stuff and I'll get back to you guys! (probably have to do it tomorrow)
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Old 21st May 2010, 01:00 AM   #10
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Are your heater wires well away from the signal wires, ie, tucked into the corners and running along the edges of the chassis coming out to the sockets only where needed? If you have to cross heater and signal wires, try not to run them parallel near each other, ie cross them at (or close to) right angles.
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