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F5 Turbo Builders Thread
F5 Turbo Builders Thread
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Old 5th June 2019, 02:02 PM   #5651
BigE is offline BigE  Canada
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Thanks!

If it makes any difference, I'm using a thermistor, as in the F5T power supply suggested by Nelson Pass.
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Old 6th June 2019, 02:17 AM   #5652
uchu007 is online now uchu007  France
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Hello

Do you connect the Gnd of power to the ground or do you lower the floating power supply?
Cordialy
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Old 6th June 2019, 08:24 AM   #5653
Dr Freeman is offline Dr Freeman
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Hi guis I'm new in this exellent forum.
Greetings to all.
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Old 6th June 2019, 09:12 AM   #5654
Dr Freeman is offline Dr Freeman
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I would kindly like your feedback on my problem:
I've purchased lsk170/lsj74 grade B matched jfets from dyaudiostore and mounted them on my F5 Turbo V1 pcb.
See image.

as you can see the jfets can be mounted and unmounted for test (red circle).


- I mount the first pair of lsk170/j74 matched.
- Power ON
- I expet 0 V bias (blu circled resistors 0.47 5W) and closed to 0 V at the output.
- Results are: 0 V bias (OK) and 0.012 V at the output (OK).
I can complete the biasing procedure SUCCESFULLY.

- I unmount the first pair of lsk170/j74 matched
- I mount the second pair of lsk170/j74 matched.
- Power ON
- I expet 0 V bias (blu circled resistors) and closed to 0 V at the output.
- Results are: 0 V bias (OK) and 0.150 V at the output (NOT OK Too high).
I can’t complete the biasing procedure SUCCESFULLY.


If I replace only the second lsk170 (suspect) with the first lsk170, I’ve:
- I expet 0 V bias (blu circled resistors) and closed to 0 V at the output.
- Results are: 0 V bias (OK) and 0.016 V at the output (OK)
I can complete the biasing procedure SUCCESFULLY but obviously they are not matched .


Besides I've an genuine 2sk170BL Toshiba. If I mount this in place of lsk170 suspect,



- Results are: 0 V bias (OK) and 0.010 V at the output (OK)
I can complete the biasing procedure SUCCESFULLY but obviously they are not matched .
What do you think?



So I think that the second lsk170 it’s the responsable.


Biasing procedure it’s obviously according to Pass (God bless him) procedure in the relative article.
I’m expert on this amplification, I’ve already built one F5 with Toshiba’s Jfets.
See my F5 (normal Not turbo).

Thank you for support.

Last edited by Mooly; 25th June 2019 at 07:29 PM. Reason: Bad (excess length) URL's removed that were affecting page loading.
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Old 6th June 2019, 09:37 AM   #5655
Dr Freeman is offline Dr Freeman
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F5 Turbo V1 Pcb and my F5
If is not visible in previus post.
Sorry
Attached Images
File Type: jpg PCB.JPG (50.3 KB, 315 views)
File Type: jpg F5.JPG (46.1 KB, 320 views)
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Old 7th June 2019, 01:38 PM   #5656
BigE is offline BigE  Canada
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Quote:
Originally Posted by uchu007 View Post
Hello

Do you connect the Gnd of power to the ground or do you lower the floating power supply?
Cordialy
Not sure I understand.

I use a center tapped transformer. The center tap is connected to the zero volt line ( power supply common ). The zero volt line is the amplifier side of the ground breaker circuit. The other side is connected to the case/safety earth.

Does that help?
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Old 25th June 2019, 05:00 PM   #5657
BigE is offline BigE  Canada
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Dr Freeman,

What are the symptoms of the "cannot complete the biasing procedure?"
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Old 25th June 2019, 07:33 PM   #5658
Mooly is offline Mooly  United Kingdom
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F5 Turbo Builders Thread


I've had to remove the links from Dr Freemans post as they ran to hundreds of thousands of characters long. This is why images wouldn't load on this page.

This is a very very tiny snippet... it took Notepad several seconds to load this even on a fast PC with SSD.
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File Type: jpg Annotation 2019-06-25 203051.jpg (724.2 KB, 284 views)
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Old 2nd July 2019, 04:06 PM   #5659
jonparkhurst is offline jonparkhurst  United States
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it is the last part I need and can't figure it out.. will someone point me to the the blue disc is the X1/Y1 rated capacitor on mouser... I have the CL 60s, but missed this one in purchase..

Thanks
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Old 2nd July 2019, 04:25 PM   #5660
Zen Mod is online now Zen Mod  Serbia
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F5 Turbo Builders Thread
you can skip that XYZ thingie
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