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PostPosted: 14 Oct 2017, 09:54 
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Joined: 27 Dec 2014, 14:15
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No exactly sure how that should look. Mine is just a stock Hammond 369AX... just like Broskie’s I think, from blog 0275


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PostPosted: 14 Oct 2017, 14:43 
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Joined: 01 Jun 2013, 09:05
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MrJackson wrote:
No exactly sure how that should look. Mine is just a stock Hammond 369AX... just like Broskie’s I think, from blog 0275



Grey wire? (probably won't make any difference) just worth a try.
https://www.hammfg.com/files/parts/pdf/369AX.pdf

Regards
M. Gregg

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PostPosted: 14 Oct 2017, 15:45 
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Oh, ok. I have a different version, without the electrostatic shield. There’s no gray wire.


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PostPosted: 14 Oct 2017, 16:53 
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Joined: 30 Aug 2017, 09:49
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Just a thought of the pc board is humming or buzzing this could cause the noise in the output of the tube d are microphonic!

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PostPosted: 14 Oct 2017, 16:57 
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If you could get your hands on a scope it could be solved in a few minutts

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PostPosted: 15 Oct 2017, 01:26 
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I’ve tried the board with two different sets of tubes. The old russians are more susceptible to vibrations (lightly tapping them produces a sound in the speakers). The EHX ones however are not. Hum level is almost identical between them.

I am planning to order a cheapo scope from ebay. I guess for “simple” home use in the audio range it should be decent enough.


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PostPosted: 16 Oct 2017, 08:14 
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I've ordered the cheapo scope from eBay... got a 10$ coupon for it as well. Can't go wrong with that :D

Anyway, I've found two other blokes that have the same issue. One of them has the first edition board (mine's rev B.). Either we're 3 idiots who couldn't figure out the instructions... or there's something slightly off with the design. Which is a real shame, as it sounds wonderful (in my setup at least, with some Dennis Had designed tube monoblocs).

PS: I've tried squeezing the trafo covers... no dice. I'll have a run at adding another polyprop. cap in parallel with C17 and see if that makes any difference (it hummed like crazy when I removed C17, so maybe... just maybe).


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PostPosted: 16 Oct 2017, 09:18 
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I threw one of these togher from parts that I have. I made it on a small chassis with point to point wireing. I used a 5y3 for the power supply. Not a fan of diodes. I tried a.c. On the heaters with Some B+ on the heaters and with out. What I found is that some tubes him real y bad the Russian 6SN7s . The U.S. Made were quite and all 6SL7 were quite. Many you have a bad diode in your power supply. This design seems to work well. I may just build a few and offer them with my PP 813's.I will say this not to put anybody's product though.Tubes and pc boards do not mix!

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PostPosted: 16 Oct 2017, 09:36 
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Alpha Wolf wrote:
Tubes and pc boards do not mix!


Why do you say that? I'm seeing a number of people transitioning from P2P to PCBs...


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PostPosted: 16 Oct 2017, 10:16 
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In doing this for over 45 years the heat from tubes caused a lot of solder joints to fail over time. Point to point is far beter. The only a pc board is used it is cheaper to make. I worked for RCA years back they used pc boards in the TV sets the made and it was nothing but prolbems. Pc boards flex a lot with the changes in remote and this causes bad solder joints over time. Hand wired point to point is far better! Any one can also together a crazy board but it takes skill to go had wore a chassis and it shows. It's just a better amp all around. look at the of Dynacoamps the used bad pc boards. I have in the past for more than a few people. Removed the board replaced it with a metal plate and re did it point to point. To make a better amp. That is not prone to falure.

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