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Old 29th September 2011, 09:37 PM   #981
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Quote:
Originally Posted by psychosteve72 View Post
thanks lazy cat, did you just mean the green junction dots? if so hows this one?
Better now

So first we'll clear out sch and you'll correct the PCB in accordance to:
- R11, R18 goes out
- C3 should be 4,7 uF so it needs more space around on PCB
- T2 you must change drain and source pin !
- please provide two 1N4007 in series diodes, parallel to C4
- please add one extra 1 uF cap parallel to C4

After sch + PCB correction I can check.

Last edited by Lazy Cat; 29th September 2011 at 09:39 PM.
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Old 29th September 2011, 09:42 PM   #982
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Originally Posted by a.wayne View Post
... can i substitute the NJL outputs for MJL , is there a difference ...?
You can, but than you will need linear Vbe multiplier (one TO-126 BJT, one diode, one multiturn trimmer, two resistors) instead of four thermal-track diodes. No big deal.
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Old 29th September 2011, 09:48 PM   #983
a.wayne is offline a.wayne  United States
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Hello LC,

Can we do the calculations for the necessary values with an PSU output of 35volt, i already have 1000va trans @ 25v..

regards,
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Old 29th September 2011, 10:00 PM   #984
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Originally Posted by a.wayne View Post
Hello LC,

Can we do the calculations for the necessary values with an PSU output of 35volt, i already have 1000va trans @ 25v..

regards,
By the +/-35V supply voltage to an output stage you will get maximally 300Wrms/1ohm, that means 25Vp and 25Ap, so you will need 4 pairs of the output BJTs and a lot of cap filtration in PSU.

Last edited by Lazy Cat; 29th September 2011 at 10:03 PM.
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Old 29th September 2011, 10:02 PM   #985
a.wayne is offline a.wayne  United States
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I have currently 200K/ uf/ch ... let me know if more is necessary ...


4 prs sound small for such a load, as do the power output from an 35volt PSU, can i ask how you are arriving at the 25 volt out from 35 volt supply...?

Last edited by a.wayne; 29th September 2011 at 10:05 PM.
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Old 29th September 2011, 10:17 PM   #986
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Quote:
Originally Posted by a.wayne View Post
I have currently 200K/ uf/ch ... let me know if more is necessary ...


4 prs sound small for such a load, as do the power output for an 35volt PSU, can i ask how are you arriving at the 25 volt out from 35 volt supply...?
100 mF per rail? It is OK


Well realistically is like that. 35V rails voltage potential (idle) -10V (rail drop + Vcesat) at 1 ohm load and you will get 25Vp and 25Ap unclipped level at amp's output and that is exactly 312,5 Wrms on 1 ohm. Four pairs BJT-s like 2SA1987/2SC5359 can handle that peak values without problems.
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Old 29th September 2011, 10:51 PM   #987
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thanks Lazy Cat,

so the extra diodes are in, but didnt know which way round? but that an easy switch. extra caps in, resistors taken out and switched round the fet.
how does it look now?

thanks, steve.
Attached Images
File Type: png psycho fet ssa.png (35.1 KB, 580 views)
File Type: png psycho fet ssa brd.png (72.3 KB, 531 views)
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Old 29th September 2011, 10:58 PM   #988
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1N4007 oposite direction, T2 is OK, funny program you are using.
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Old 29th September 2011, 11:10 PM   #989
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swapped diode round,

program is eagle lite on an ubuntu linux pc.

thanks for the help, steve.
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File Type: png psycho fet ssa.png (35.0 KB, 506 views)
File Type: png psycho fet ssa brd.png (72.2 KB, 535 views)
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Old 29th September 2011, 11:30 PM   #990
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One more thing regarding PCB:
- Q1 and Q3 have to be face to face glued together. This is mandatory.
- Q2, Q4 each should have small heatsink, also mandatory.
- T1, T2 probably there will be Al L-profile fixed to heatsink? Provide good thermall contacts ...

That's it. Bye
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