F5c V2.0 Cascode Build Documentation - Page 2 - diyAudio
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Old 10th February 2013, 01:14 AM   #11
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Coils said:

...if so maybe those Jensens make a diff, as your amp is biased higher than mine. I used panasonics.


Coils,

I just reread your note on the 4 pole caps and refer you to this document we found of assistance when picking up the Jensen caps a couple years ago, for what it's worth.

http://jensencapacitors.com/public/dokumenter/4pole.pdf

Steve
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Old 10th February 2013, 05:19 AM   #12
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Coils,

I just looked at the current BOM and schematic posted at the store for the FVc V2.0 board that we used. Still confusing. The schematic shows the voltage dividers for the cascode transistors to be 10 ohms (R101, 102, 103, 104), which is incorrect - this would be 1.7 amps through each rail to ground (34 volts through 20 ohms). I assume they meant to have them be 10 K ohms. And the BOM shows them at 4.7K ohms, which would be fine. As I pointed out in our build document, 4.7K or 10K or something similar is fine, as long as they are all the same and of high enough resistance to limit current to something safe and manageable.

The schematic also shows a thermistor on each MOSFET, rather than just on the center two, as is found on the board.

Steve
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Old 10th February 2013, 08:22 AM   #13
zoe is offline zoe  United States
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yes I see what you mean.I don't think that's right. I would adjust values with the F5T article from Mr Pass as illustrated in the V3 version
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Old 10th February 2013, 01:20 PM   #14
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Oops. Meant to post the last one to zoe - but that appears obvious. Too little sleep.

Steve
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Old 10th February 2013, 07:09 PM   #15
coils is offline coils  United States
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Quote:
Originally Posted by toxic ingestion View Post
Thanks for the info, I have Jensen 4 poles in my diy F3, I think I will open it up and do some measuring.
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Old 14th February 2013, 05:56 AM   #16
zoe is offline zoe  United States
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I am going to build a F5TV1 with the F5C boards here is some pictures of my boards
Attached Images
File Type: jpg F5T 001.JPG (575.3 KB, 512 views)
File Type: jpg F5T 002.JPG (598.3 KB, 483 views)
File Type: jpg F5T 003.JPG (549.9 KB, 466 views)
File Type: jpg F5T 007.JPG (552.2 KB, 448 views)
File Type: jpg F5T 008.JPG (527.0 KB, 439 views)
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Old 14th February 2013, 02:52 PM   #17
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Zoe,

Looking good. Nice job on the resistors on the bottom side. I see parallel 5 watt 1 Ohm resistors on the sources of the MOSFETs. What are you shooting for with regard to bias, or is that just what you had lying around? That should sure do the job.

Just a note: on the photo of the underside of the board, some of those soldering connections look like they could be cold - but a photograph can be very deceptive and you obviously can see it much better than I.

What are you using for MOSFETs?

Steve
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Old 14th February 2013, 07:18 PM   #18
cviller is offline cviller  Denmark
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Thanks for putting together such a fine piece of documentation!!

I have added a link to my F5 blog post.
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Old 14th February 2013, 07:57 PM   #19
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Now if only the boards were back in stock...
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Old 14th February 2013, 08:08 PM   #20
cviller is offline cviller  Denmark
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I read somewhere that someone was working on F5T - I suppose that is what people are waiting for.
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