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Old 17th February 2010, 12:45 PM   #7101
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here's how I implemented a soft start based on the CL60 and a timer circuit from Sylvain Bergeron.

The soft start has its own small transformer and power supply, the switch on the front panel activates the soft start:
a double relay is switched on that puts the mains on the 500VA transformer with a thermistor CL60 in series,
after two seconds that thermistor is bypassed with a second relay, so that the mains is directly connected to the 500VA.

Some remarks about the circuit:
- you can omit or change the resistor R8, I needed it to drop the voltage to the relays.
- You can put a led in series with R5 bleeder resistor as power on light.
- I used dip switches with R1-R4 so I can choose the delay of relay 2.

Regards,
Danny
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Old 17th February 2010, 01:09 PM   #7102
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One more question about R15/R16 ...

I built the "Cvillar Board" version with cascode and double output,
only R115 and R116 is installed. With 2K2 an TH01/TH02 at 4K7 I
could it only get biased to 200mV. I changed R115/R116 to 7,5k
but now I think thermal regulation is not working. To turn Bias to
0,6V in this setup without a prob is possible.

So maybe 4K7 could be better choice ??? Any ideas ?

Michael
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Old 17th February 2010, 02:46 PM   #7103
cviller is offline cviller  Denmark
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4k7 is probably better, but some people run the amp even without thermistors. The effect of your thermistors is relatively small now, so if you run into problems with keeping the dc offset down, then you might want to find some other thermistors.
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Old 17th February 2010, 04:14 PM   #7104
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by danny_66 View Post
here's how I implemented a soft start based on the CL60 and a timer circuit from Sylvain Bergeron.
I like this set up.
What is Vgs of the 610 after the mpsa56 has fired to pull in the FET fast?
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Old 17th February 2010, 08:27 PM   #7105
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Quote:
Originally Posted by cviller View Post
4k7 is probably better, but some people run the amp even without thermistors. The effect of your thermistors is relatively small now, so if you run into problems with keeping the dc offset down, then you might want to find some other thermistors.
Without was my test. Now with TH01/02 4K7 and resistors at 6K8 works fine.

Michael
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Old 18th February 2010, 05:09 PM   #7106
hags is offline hags  United States
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Default Fairchild MOSFETs

I puchased a large quantity of Fairchild FQA12P20/FQA19N20C pairs in order to receive quantity pricing.

I have more than a few left.

I think $12.50 per pair shipped in the contiguous U.S. is a fair asking price.
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Old 18th February 2010, 05:27 PM   #7107
EUVL is offline EUVL  Europe
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$4.00 a pair. Sorry.

Patrick

PS There are lots of people here who got hundreds during the group buys.
I am sure they are more than willing to part with them at USD12 per pair.

Last edited by EUVL; 18th February 2010 at 05:38 PM.
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Old 18th February 2010, 05:31 PM   #7108
EUVL is offline EUVL  Europe
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Someone asked me through PM about why I used different source and feedback resistor values for the 2SK170 and 2SJ74.
This has been explained multiple time in this forum, so please read through them first before you ask.
It is only applicable when you use 2SK1530/2SJ201 MOSFETs for the output stage, and that you want to do gain balancing for the positive and negative half.
You do not have to use these different values.
It still works with values from the original article.


Patrick

Last edited by EUVL; 18th February 2010 at 05:38 PM.
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Old 18th February 2010, 05:50 PM   #7109
hags is offline hags  United States
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Quote:
Originally Posted by EUVL View Post
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$4.00 a pair. Sorry.

Patrick

PS There are lots of people here who got hundreds during the group buys.
I am sure they are more than willing to part with them at USD12 per pair.
Mine are geniune Fairchild parts and matched. Thanks for your input though.
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Old 18th February 2010, 05:55 PM   #7110
EUVL is offline EUVL  Europe
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Are you suggesting that those from jackinnj or from the Group Buys are not genuine Fairchild parts ?

Patrick
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