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Old 22nd July 2012, 01:42 AM   #12491
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Quote:
Originally Posted by noSmoking View Post
lol,Thanks
Its a very tidy kludge! nice.

Russellc
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Pass DIY B-1, Pass DIY F-5
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Old 22nd July 2012, 02:24 AM   #12492
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Quote:
Originally Posted by noSmoking View Post
Hi jackiNJ,
You teasing us ,lol
Nope

I had some boards burned to replace those I'd been using for (I guess) 3 years, but when taking a really hard look at the performance there are a couple more things I would change. I also made a 'boo-boo' in the protection scheme == easily rectified. There's provision for a 100pF cap on the input and a zobel on the output. I also find it helpful to put some some capacitance on the board for local decoupling. You can sub a pair of 2N540's for J74's and get the 1W THD% around 0.003%. Anyone who wants boards they're free ex postage and the PayPal fee.

FWIW, I have never been happy with the foldback overload protection. In fact, I am coming to Peter Daniel's view of just eliminating the protection altogether, although Sister Blanche Marie O.P. would have me assigned to the lowest ring of Dante's Inferno. It just takes more patience to adjust it right.
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Old 23rd July 2012, 03:32 PM   #12493
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Said before that i wasn't too happy with the current limiting on the F5 -- so i did some simulations with the original design and the F5-R1. In the latter, the thermistor is connected directly to the source, no longer in parallel with Q5. According to the original article, current limiting was to take place @7A.

The load is a "Voltage Controlled Resistor" which is varied from 0.1R to 10R.

Click the image to open in full size.

If you did as I have, i.e. change the output MOSFET source resistors, the value of R17 should be changed as well.
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Old 23rd July 2012, 03:50 PM   #12494
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Hi jackinj,
I'll try that ....
Thanks,
NS
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Old 23rd July 2012, 03:58 PM   #12495
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Default hi Russelle,

Quote:
Originally Posted by Russellc View Post
Its a very tidy kludge! nice.

Russellc
It works ,I guess some folks don't like patches,lol What werks is ok for me,lol!
You know I am amazed with this amp,I have some old RS meters for speaker outputs ,I am putting 5 watts out and it's pretty loud,
I use a pair of kustom 200 watt stage monitors,kinda my test speakers,I don't know the spl,but they drive pretty ez,kinda blows you away,,,,GREAT design Nelson,Thank You!
thanks!
NS

Last edited by noSmoking; 23rd July 2012 at 04:05 PM.
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Old 23rd July 2012, 06:05 PM   #12496
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If it folded back, the curve would look something like this (LM723 15V regulator with foldback regulation at 2 amps):

Click the image to open in full size.
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Old 23rd July 2012, 06:58 PM   #12497
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hi Jackinj,
Would you run that with 220 R and .5 R for me,Thanks,
Ns
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Old 23rd July 2012, 08:08 PM   #12498
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hi jackinnj,

did you receive my messages?

regards,
matthias
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Old 24th July 2012, 11:48 PM   #12499
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Default 4PC 4.7K Thermistor needed

Hello
Do someone has 4PC extra 4.7K thermistor at hand?
I would gladly buy them in case you not planing to use them. To order from Mouser etc the shipping cost more than the parts. From Epay I do not want to buy components, I did learned the hard way.
I have all the parts for the F5 Turbo V1 just I need the thermistors..
My plan to use 3 or 4 pair Toshiba 2SK1529/2SJ200 28-30V rail Voltage with out cascoding..
Also to order I have to know what type feet my need here. Would be better if someone has 4PC and I would take them over.
Please let me know.
gaborzoltan2@gmail.com
Thank you very much
Greetings Gabor

Last edited by gaborbela; 24th July 2012 at 11:51 PM.
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Old 25th July 2012, 07:53 AM   #12500
slungu is offline slungu  Germany
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Ok, I'm not sure if I should open another thread or ask here, but I plan to build two F5 mono blocks and had some questions.
First I would like to keep them small, and was thinking about going with 2x15V 160VA transformers instead of the original 2x18V. Reason would be to need less heat sink area and be able to build them "smaller" so I was hoping to have to loose less power trough the heat sinks. And then : does anybody have a link to a nice calculator for heatsinks ? I once had a link for a very nice calculator that would show the heat on the heat sink depending on positioning and so on - really very nice in order to optimise the placement of the heat sources, but I can not find it anymore.
So, has anybody tried a "undervoltage" F5 ?

Regards, Stefan
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