diyAB Amp The "Honey Badger" build thread

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#2,661
AndrewT said:
Rth j-c does not change with de-rating. Rth j-c is determined by the physical size of the device backplate. It can be determined from the device data.
Tj= Tjmax and Tc = 25degrees (the starting point for all manufacturers) leaves the delta T = 125Cdegrees.
The power to be dissipated is Pmax = 125W
Therefore Rth j-c = 125C/125W giving 1C/W I usually work from Ta @ highest summer temperature up to the Tc value after the heat has passed through the sink to ambient , Rth s-a (de-rated), sink to device Rth c-s and junction to case Rth j-c, to find the worst case average junction and case temperatures for the sink I propose to use. I then add on an extra 5Cdegrees to cover for one or more devices being slightly hotter than the average.
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Do you have time to make some calc for me ?

I would like to be sure my match is acceptable
 
#2,663
anatech said:
Hi audiofan,

For starters, light bulbs are highly variable in resistance. You can buy 8 ohm, non-inductive loads off Ebay for very little cost. There is no reason to have to be creative.

-Chris
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If I had this problem I would test transformer with a lightbulb , ( tranformer alone ) if there is no noise with a resistive load then I would test rectifiers & capacitor , if rectifiers or capacitor are defective maybe it will work as a very unbalance load ... and current will no be symetrical .. then magetisation is not symetrical .. and noise start from there ...
 
#2,665
First thing to know is secondary volatge .... nominal current ..&..the VA rating of the transfo

But you may also try with a low wattage bulb and see how it goes...

If secondary volage is below 120 volts the bulb will not be as bright as usual... will glow as if you were using a dimmer ..this is normal .... with a multimeter you can measure current ... and change the bulb ...
 
#2,666
BobEllis said:
E-waste sounds like what my girlfriend would call my electronic projects. 😱

I'm building my amps in the 4U deluxe case at least partially in an attempt to appease her sense of style. I asked if she preferred the plain face or with handles. Her response was that a TV, cable box and Bluray player were enough electronics for our living room. Uh Oh. Guess I have to figure a way to hide the equipment rack and make my speakers look like sculpture.
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Haha! :-D

Something off topic to this - I'm a ham radio guy, and few years ago I was in contact with a man from UK on shortwave.
We talked about antennas.
Antennas are sometimes funny to work with. One day you can explain why the antenna doesn't work....and the next day you can't explain why it works and so on. 🙂
So the final thing is, that you sometimes can't figure out the antenna why it works as it does.

The answer from UK was: It's because the antenna is >female< !!! :-D
I nearly hit the floor in a BIG laugh! 🙂

Well, yeah - here in Denmark we have the same issues with women and HIFI.
 
#2,674
Go and read the links in posts 2669 and 2672.
You will see those same differences.

It's a problem with very complex MENU systems. There are multiple ways to get to apparently the same end.

But the different routes actually give different outcomes.
It's similar for "attaching" pics and such.
The Forum is aware that using the alternative menu routes gives different outcomes, but they have not removed the problem.
Maybe the new software will remove the anomally.
 
#2,678
The Firefox method that usually works is to right click on the post number and use "Copy Link Location".
Then paste that into your post. The alternative for MS internet explorer is to "Copy shortcut" and paste that into your post.
Both these normally exclude the page number and that way all Members whether using the default posts per page or their special posts per page get directed to the correct post.
 
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