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Recently I have replaced a LM317T voltage regulator of my CD player with a LT317AT from LINEAR TECHCNOLOGY. However, the new voltage regulator runs now EXTREMELY hot, while the former, the LM317T, ran merely hot.Are the LM317T and the LT317T not always interchangeable?
Any comment about this ?
Follow Ups:
My only comment is that I hope someone with the answer posts it! I was just about to do the same thing in the power supply of my McCormack phono section, and would love to know if it's a direct swap.Have you done any measurements with a meter to see if you're dropping the same voltage as before?
Yes, I have made measurements and the voltage is the same as before.
Look up decoupling in the data sheet.
I changed it because I read that the LT317AT is a higher quality variant of the LM317T.The input has been bypassed using a PANASONIC FM 25V/100uF capacitor, and the output has been bypassed using a SANYO OS-CON 10V/100uF capacitor.
Oscon too low ESR I think
Where is the problem in using very low ESR capacitors for bypassing the output of LT317AT voltage regulator?
The output of the reg needs a little resistance or inductance to be stable. Try either moving the OSCON a little futher from the reg (more inductance) or add a low resistance, say 0.1 - 0.3 ohm resistor from the positive rail to the cap. Either method will allow the reg to work well with the OSCON.
The output voltage will be more stable. This should also improve the sonics. Too low ESR is a real issue, just like too large a cap close to the reg. I have seen lots of regs with a 1,000 ufd cap on the output. I think a 100 ufd is way more than needed.
I do not know how many are left, but a great low cost cap for regs is the Silmic II. They were dirt cheap at Digikey. I do not know if you can get enough to make a 25.00 order though. But maybe combined with some more regs you may get there.
Another tip, always use the series resistor. I like a 0.1 - 0.2 ohm and then use whatever cap I have. This does make a difference.
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