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Old 20th October 2011, 08:03 PM   #631
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I fixed the problem: was inversed polarity in the Trident clock reg. Now is going on perfectly well.

Last edited by merlin el mago; 20th October 2011 at 08:08 PM.
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Old 20th October 2011, 10:02 PM   #632
Salas is offline Salas  Greece
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Quote:
Originally Posted by coolhead View Post
Voltage across R301:
6.3Vac trans = 1.31V
9Vac trans = 1.36V

R301 is 10ohm

The output is the same 3.3V, the different will be CCS current of 50mA.
The Mosfets show a VDS (drain to source voltage) response reflecting to their VGS also, over a region, especially over first 50V in 200V devices. They state the VGS when VDS about equal. That is why your graphical calc was spot on at about 5V across. This type here also shows a quick reduction in its capacitance (3 kinds) at over 5V across, leveling out gradually till over 30V across. That's another reason I recommend 5V drop as minimum. You got to have a known Vin so to set a current exactly. If you want to subjectively compare transformers, you got to compare at same CCS current & Vin. Liking it with +50mA is a hint that more CCS is possibly beneficial to your application regarding the reg. Something that hot-rod users take to extreme some times. We usually set it at 200mA no matter if our load need is miniscule in Hypnotize DCB1.
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Old 21st October 2011, 12:55 AM   #633
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Quote:
Originally Posted by merlin el mago View Post
This current have to be for a Trident, wich one XO, right?
Yup, is for VDD_XO, cause that is a pian on the back, it is so loss, I have experience 2 failures here, every time is op amp burnt.
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Old 21st October 2011, 03:29 AM   #634
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Quote:
Originally Posted by AndrewT View Post
and now turn the mains supply voltage down to suppliers specified minimum. Measure again.

The fact that you have already lost 50mV tells me you are getting close to dropping out.
Andrew,
Too bad I don't have a Variac to test out the minimum supply specification.

So, in theory if I do have a variac and turn down the supply voltage from (240Vac) to the minimum specify (220Vac), the 6.3Vac toroidal trans will drop more in voltage across R301 as compare to 9Vac EI core trans?

Actually the 6.3Vac toroidal trans is written 75VA while 9Vac EI core trans only 20VA, I would expect it can give better stability than 20VA trans.

Can we say the voltage rating of secondary output is more important than power rating of the trans if the demand is within power rating range?

Thanks.
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Old 21st October 2011, 04:31 AM   #635
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Just measure the AC available on the secondary when loaded with your reg at your listening sessions times. On working days and on weekend. That will pretty much give you an idea of where your mains vary for your purpose. If they vary appreciably that is.
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Old 22nd October 2011, 01:56 PM   #636
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Default TP Legato 1.0.3

Just finished my BiBs to power TP Legato 1.0.3 that needs +-15V & draws 360mA, the positive rail works perfect but negative rail only reach -10.35V, both rails:

-TX 30VA dual secondary 15V 1A (one secondary for each rail)
-Mains filter cap 10.000uF 63V
-Rectifiers Fairchild Stealth
-Voltage reference 10V-25V Mosfet reg. 2 1.9V LED, 1.8 kOhm R303. 5K trimmer. Other parts jumper.
-Dummy load 44R 0.34091A (it's the more aprox. value that I have on hand)
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Old 22nd October 2011, 02:48 PM   #637
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Check that the negative rail has enough CCS first. See if you chanced on unusually low IDSS Q203 next, if CCS is OK.
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Old 22nd October 2011, 03:08 PM   #638
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Both rails R101-301 3R9, measured: positive 4R10 negative 4R08
Positive rail 0.379A
Negative rail 0.235A you are right
Dummy load: positive 43R9, negative 44R0

If Legato draws 360mA I have to set the current BiBs to 1A, or it's too much?
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Old 22nd October 2011, 03:22 PM   #639
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Set ~550mA. At 200mA spare they grip well.
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Old 22nd October 2011, 03:24 PM   #640
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