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Old 25th February 2013, 06:57 PM   #231
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After all resistors were installed, I soldered the capacitors and the Zetex devices (ZTX450 and ZTX550)

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Soldered the JFETs, mounted on the heat sink and started it.

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The rails were set to +23V/-23V using a Variac and two handheld meters not shown in the picture. The top meter shows measurement across R8, the one in the middle across R7 and the bottom meter shows the DC offset at the output.

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Attached Images
File Type: jpg BoardOnHeatsink.JPG (191.6 KB, 391 views)
File Type: jpg MeasurementPoints.JPG (157.0 KB, 380 views)
File Type: jpg Measurements.JPG (182.3 KB, 370 views)
File Type: jpg Caps1.JPG (79.8 KB, 366 views)
File Type: jpg Caps2.JPG (90.6 KB, 368 views)
File Type: jpg Caps3.JPG (92.9 KB, 370 views)
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Old 25th February 2013, 07:11 PM   #232
Marra is offline Marra  United Kingdom
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Neat.
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Old 25th February 2013, 07:13 PM   #233
PKI is offline PKI  United States
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What can I say — such an amazing porn! :-) Very nice job!
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Old 25th February 2013, 07:22 PM   #234
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Default About the board

The holes for the Zener need to be increased. Fairchild devices will not fit, Vishay ones did fit but were very tight. I worked on them using 220 grit sandpaper and polished them with 00 steel wool.
Another issue was the edge of the board where the MOSFETs are mounted. It projects over the body of the devices and, in my case, using 5mm tall standoffs the PCB was touching them. I worked around that raising the standoffs with washers. Looking at the picture showing the board mounted on the heat sink, it is easy to tell that the distance from the mounting holes to the edge of the board is shorter at the top than it is at the bottom. I think we can safely trim that bottom edge, making the board the same exact dimensions as the F4 PCB and, at the same time, resolving the problem described above.
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Old 25th February 2013, 07:23 PM   #235
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Thanks Marra and PKI. I am glad to be able to help.
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Old 25th February 2013, 07:25 PM   #236
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Excellent documentation.
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Old 25th February 2013, 07:36 PM   #237
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Default About my build

I managed to assemble both boards but was only able to start one of them. Because of unexpected delays on Sunday it was late in the evening when I finally fired up the first channel. At 1 KHz the square wave looks great, at 500 Hz top and bottom are slanted and, at 10 KHz, the sides are sloped. Feeding directly from a CD player the sound was clean however, using the same player on the F5 it played much, much louder. I did connect the Aleph J's negative input to ground.
In the coming days I will perform additional measurements and post images and values. I wanted to complete the build to confirm that the PCB works and report the issues I found.
Those of you who have already built an Aleph J may be able to give me some feedback on the measurements posted so far.
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Old 25th February 2013, 07:47 PM   #238
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They look perfectly fine to me.
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Old 25th February 2013, 07:48 PM   #239
henryve is offline henryve  South Africa
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BTW, I have also updated the BOM to Rev B. Added Silmic 35V and Panasonic FM caps and also used Didiet's latest schematic.
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Old 25th February 2013, 07:49 PM   #240
Zen Mod is offline Zen Mod  Serbia
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make all necessary measurements ( DC ) , mark them on schmtc and post

regarding pcb touching body of mosfets - either higher standoffs or leaving mosfet legs longer , before bend
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