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Old 8th April 2010, 05:03 AM   #1271
ra7 is offline ra7  United States
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Hey guys,

the 2k2 resistor near the power led is for the led itself right?
I don't have a 2k2 on hand so I'm planning to stick something close in there.
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Old 8th April 2010, 08:05 AM   #1272
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Quote:
Originally Posted by ra7 View Post
Hey guys,

the 2k2 resistor near the power led is for the led itself right?
I don't have a 2k2 on hand so I'm planning to stick something close in there.
If it's for the LED, doesn't matter the exact value. Just use ohm law to set it to something between 2 to 15mA, depending of how much light would you like to have.
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Old 8th April 2010, 10:26 AM   #1273
vgeorge is offline vgeorge  Greece
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Nice. Are those sinks OK, or too hot? Could go on the box floor too. Especially if reinforced with an aluminum plate. But if its reliable as it is, forget it.
Voltage drop on R1 is 1.9v, so current must be around 260ma. Heat on the fets is 53 celcious max, after been on for 2 days continuously, so I do not worry much. I have my phono shunts run a lot hotter for a bout a year with no problem!
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Old 9th April 2010, 06:51 PM   #1274
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@vgeorge: mine was dying after some days of usage, some pins almost short when i test using ohmmeter. Better use bigger heatsink IMO.
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Old 9th April 2010, 10:10 PM   #1275
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Just an update to my previous saga of attempting to use the Fairchild FQA* counter parts of the IR's. I measured all other transistors and resistors. They all measured correctly, but I replaced them anyway. Unfortunately, the situation did change by much. So, my conclusion is, either I really screwed up something at the board (yeah, I have lifted a few pads out of so many desolderings :-)) or the P-channel FQA* is not suitable to this use.

I have ordered a few IRFP9240's. Once they arrive, I'll put them in for a quick test. That should tell me one way or the other. If it works, then it will be a forgone conclusion that the Fairchild P-channel is not a direct drop in into this board. Stay tuned!!
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Old 10th April 2010, 05:15 AM   #1276
ra7 is offline ra7  United States
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I'm trying to match the led strings... and measured individually, i'm getting most leds at about 1.95V... measured as a string, i'm getting about 8.80V (string of 5) and 5.65 (string of 3).

Is that ok? i'm pretty sure I can match both shunts at those values.
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Old 10th April 2010, 05:23 AM   #1277
Salas is online now Salas  Greece
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They would sum at 9.75V if you had more than the 9V battery. When the lot of 3 seem logical at about 1.9V average. Just check the 5 string candidates in duets and triplets and set them aside to calculate two matching 5 strong strings.
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Old 10th April 2010, 05:26 AM   #1278
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So then two strings closely matched at 9.75V are ok?

Thanks Salas! What would I do without you!
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Old 10th April 2010, 05:49 AM   #1279
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OK.
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Old 10th April 2010, 08:00 AM   #1280
vgeorge is offline vgeorge  Greece
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Originally Posted by sutantoroy View Post
@vgeorge: mine was dying after some days of usage, some pins almost short when i test using ohmmeter. Better use bigger heatsink IMO.
What temperature did you have on the fets?
I have 2 other shunts and an F5 running hotter than this and survived previous Greek summer with no AC!
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