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PostPosted: Mon May 14, 2012 1:07 pm 
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I finished my amp yesterday.
Unfortunately, I made one mistake and wired the red lead from the OT to the wrong spot on the board. :bugeye:
I wired it to the first hole, where the 250R 5w and the 25uf cap are.
When I powered it up I had a little puff of smoke that appeared to come from the area of the 4K7 and 22K resistor.
I corrected my mistake and checked the values of those resistors and they were fine.
I checked my voltages with the rectifier tube in and I was not seeing 22 vdc on pins 8 of V4 and V5.
I was not certain if those voltages should have been measured with tubes in or out.
So I put the tubes in and the amp came to life.
It is very quiet from a noise perspective. There is very little ambient hiss even with all controls dimed.
All of the inputs work and the VRM too.
The sound has a ton of variations depending on the control settings. I was using a new-to-me Eric Clapton Strat, which has the booster circuit in it that I am still getting used to.
My wife asked me to turn it down in deference to the neighbors at one point, so it’s pretty loud. 8)
It is a bit farty in some instances.
Since I have never played through one of these before, I was wondering if there is anything I could have toasted when I mis-wired the OT.
Also is the tip of the speaker jack + or -?

Thanks,
Scott


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PostPosted: Mon May 14, 2012 5:53 pm 
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Measure all voltages with tubes in.

Replace the 22K, 4.7K and 250R resistor to be safe.

Tip is +

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PostPosted: Mon May 14, 2012 9:49 pm 
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Thanks Kurt.
I measured the values of those resistors and they are all spot on.
Here are my voltages:
Mains 117
B+352
Pin 1---2---3--- 4 ---5---6---7 ---8
V1 125---1.85---/---/---123---/1.85
V2 156 ---1.16---/---/---156---/42
V3 ---/---346-315---/---/---/---20
V4 ---/---346-315---/---/---/---20

So pin 8 on V2 is way low, yes?
Everything else seems pretty good.

Advice?

Thanks,
Scott


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PostPosted: Wed May 16, 2012 5:39 pm 
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What rectifier brand are you using?
Can you get the wall voltage to 120V and measure all the voltages?

Check all your resistor values.

In the end though as long as the amp works and sounds good that's all that matters. The voltages don't have to be exact, these old tube designs aren't a precise science (epically the Tweed Deluxe).

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PostPosted: Sat May 19, 2012 2:32 pm 
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Thanks kurt,
I don't think there is much I can do about the mmains voltage. The rectifier is a JJ I believe.
Based on conversations with you and Steohen, I think I'm all set!
Yeah, successful first build!!!


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