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Old 24th November 2008, 12:55 PM   #111
N1ESE is offline N1ESE  United States
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Nate,

Here is a good overall shot at high-resoulution that covers just about everything. Some comments about what's going on here:

For grounding the board and commons on the input, I am using the extra ground pad that's in the middle of the two input terminals. From the pot, the middle pins go to the outer most pads on the board (signal in) and the right pins go to the inner most pads (common). The center common pad is wired to ground. Left pins on the pot goes to the Left (Tip) and Right (Ring) on an 1/8" jack. Shield is wired to the earth ground. If I completely remove the input jack and pot and hard wire the terminals directly to my source, performance is the same. When I do this, I wire the tip to the left outer most terminal and the ring to the right. Shield is then wired to both inner most terminals. I have also tried floating the shield with no difference.

As you can see, oil cap is not wired at this time.. just the choke.

Outputs currently wired for UL mode. Amp behaves roughly the same when wired for Triode mode.

Everything is star grounded to the earth ground on the power cord. The second link shows the ground lug.

Speaker wiring: 8-ohm is yellow, white is common, the black goes to earth ground as shown on George's wiring diagrams.

Pics:
http://img529.imageshack.us/img529/6535/overallqf5.jpg
http://img529.imageshack.us/img529/3858/groundnr4.jpg
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Old 24th November 2008, 01:15 PM   #112
n_maher is offline n_maher  United States
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Well, not that it makes you feel any better but I don't see anything jumping out at me that looks incorrectly wired. I'm useless to you.
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Old 24th November 2008, 01:20 PM   #113
N1ESE is offline N1ESE  United States
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Quote:
Originally posted by n_maher
Well, not that it makes you feel any better but I don't see anything jumping out at me that looks incorrectly wired. I'm useless to you.
Yeah, I'm stumpified. The wiring is pretty basic, I've been building amateur radio gear for years so I generally can wire stuff up properly and have a good grasp of basic electronics. I pretty much followed George's wiring drawings to the letter.

You're not useless if you are sending me a couple input tubes to try. I appreciate it. It could very well be the input tube still. I dunno.
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Old 24th November 2008, 03:08 PM   #114
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Ty_Bower


You won't have a steady reading unless you've got a signal generator handy. Music is going to bounce around all the time.

Remember the 12AT7 in this circuit has a gain of about 50. If you see 285 mV to its grid, then you should be getting over 14 volts to the KT88. You reported a while back that you got about 315 mV. Something is wrong around that first stage...
Actually he does have a signal generator handy. If it's driven from a computer, just look on the net for a freeware signal generator, or even find some tone samples. All you need is something in the range of a couple hundred Hz to a couple kHz. Measure the AC output from the sound card on your Multimeter, then check AC levels all along the signal path, i.e., input grid, input plate, output plate, speaker output. Note that as long as you are using a single test frequency, you don't even need a true RMS meter. If your meter can't handle the DC offset voltages, use an inline cap - something like 0.1uF will do fine.

Sheldon
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Old 24th November 2008, 03:12 PM   #115
N1ESE is offline N1ESE  United States
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Quote:
Originally posted by Sheldon
Actually he does have a signal generator handy. If it's driven from a computer, just look on the net for a freeware signal generator, or even find some tone samples.
Excellent idear, why didn't I think of this. duh. I will try this in a couple hours and report back.
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Old 24th November 2008, 03:19 PM   #116
Sheldon is offline Sheldon  United States
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You will find it very instructive. BTW, do keep your output transformers loaded. You can use the speakers if the level is not too high, but that can be annoying. Tip em over onto carpeting. But keep the level below loud listening levels or you could toast the drivers. Or, safer, use a load resistor. An 8R power resistor is ideal, but you can use significantly higher or somewhat lower values too. Parallel up some resistors if you don't have one big one.

Sheldon
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Old 24th November 2008, 03:24 PM   #117
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I'd suggest either of these pieces of software...

http://www.fesb.hr/~mateljan/arta/download.htm

http://www.zeitnitz.de/Christian/Scope/Scope_en.html
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Old 24th November 2008, 03:48 PM   #118
w5jag is offline w5jag  United States
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What are the voltages on each side of those orange drops?

Win W5JAG
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Old 24th November 2008, 03:54 PM   #119
N1ESE is offline N1ESE  United States
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Alright, software installed and configured. I'm generating a 1 KHz signal and showing 0.989 VAC on my lineout from the PC. Time to start testing the various stages now that I've confirmed I have close to a 1 VAC output. Just need to see what I have for power resistors before I begin.
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Old 24th November 2008, 04:09 PM   #120
N1ESE is offline N1ESE  United States
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Quote:
Originally posted by w5jag
What are the voltages on each side of those orange drops?
236VDC on the one side and then about 0.485 VAC on the other side with a 1 KHz tone injected in.
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