Scott LK-72A is ALIVE - diyAudio
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Old 14th November 2006, 04:04 AM   #1
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Join Date: Sep 2006
Default Scott LK-72A is ALIVE

First, I want to thank the forum for helping me on the basics which enabled me to bring this thing back to life.

After conducting a few tweaks tonight I decided to hook some decent speakers up to it for the first time and give it a bit of a serious listen - so I grabbed my Sherwood CD-980 player and my kit speakers and yes, Zappa's Apostrophe <grin>.

I'm still running the original cans but this thing is dead quiet and all the measurements look pretty good so I've decided to wait a little while before putting the replacements in. Those are JJ 7591's (much larger than the originals and capable of rubbing against the opt's like wild dogs), the original Scott labeled 6gh8 together with an old Sylvainia I found, and yes the original 5ar4 is still doing the trick. Also, all four of the 12ax7's are the ones Dad put in, back in '63 after finishing the assembly.

Click the image to open in full size.

Three of the original 7591's still had some life in them but I was getting some funny numbers from them so decided to put them aside. The original selenium rectifier was toast, one of the 6bh8's was a hummer, some of the ceracaps looked like they had leaked some wax-like stuff and the selector switch was dead frozen. So I've been banging away on this thing for the last few weeks getting the bugs out. Literally, yeah there were bugs too...

Click the image to open in full size.

I've got the shields for the 12ax7's but they look like cr*p because the amp was in my brother's basement for 20 years keeping the sump-pump company. Glad the chassis is aluminum... I think the aluminum angle you see bolted on near where the opt wires go through the chassis is acutally a heat sink that transfers the heat from the opt's (that transfers from the 7591's) to the bottom cover. Tubelab is dead on about the low power computer fans - just enough power to move the air around a little bit makes an incredible difference in the heat conducted into the output transformers.

Click the image to open in full size.

I've yet to find a resistor more than 10% off and no bad joints (thanks dad). Oh yeah, and he was a wrapper, getting some of the old caps out got me cursing a tad.

Click the image to open in full size.

Oh yeah, so I should mention that it is sounding SWEET! Soundstage is awesome, very smooth clean clear sound, easy on the ears - no fatigue at all after a few hours. I put some Steely Dan on (Everything Must Go) and got this huge stupid smile on my face. Very tight, clear, no harshness or distortion at all. All the eq pots, I still have centered... like I forgot they were even there.

Special thanks to Gingertubes who took some real time to explain some basic testing procedures etc.

I'm now waiting for my Stromberg Carlson asr-433 12wpc to get delivered <read sleeper> - can't wait to start on that baby. I might be getting hooked on this.

Cheers, Ed
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Old 14th November 2006, 04:45 AM   #2
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Right on! Nice work!

I'm familiar with the big stupid smile syndrome.
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Old 14th November 2006, 11:12 AM   #3
SY is offline SY  United States
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Location: Chicagoland
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You've taken the needle. It's a long, downward spiral of addiction from here on out.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 14th November 2006, 12:19 PM   #4
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Join Date: Sep 2006
But I was just tempted... you know, - to try a little... It came out of the blue, I don't know what I was thinking... - so I did try it...
SY, you've got to help me! I didn't know it was going to be like this! How do I stop now???

Excuse me...
I have to go open the windows in my listening room now, It's getting bloody hot in there. Hey, you got any tubes?

Cheers, Ed
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Old 14th November 2006, 01:45 PM   #5
Sherman is offline Sherman  United States
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Location: Chicago area
Oh, you can't/won't be able to stop now! To quote Pink Floyd, "Welcome to the machine!"
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