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JL300/2 power supply problem? - pls help
JL300/2 power supply problem? - pls help
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Old 24th January 2019, 01:59 AM   #11
nonprof is offline nonprof
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by Perry Babin View Post
Pin 1 is the feedback for the voltage regulation. It goes back to U701 on the PS driver board. Post the DC voltage on all terminals of U701.
Hi Perry! Here are the measurements,

U701
Pin 1. 0
2. 0
3. 0
4. 0
5. 0.916
6. 1.82
7. 0.12
8. 10.89
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Old 24th January 2019, 02:59 AM   #12
nonprof is offline nonprof
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by nonprof View Post
Hi Perry! Here are the measurements,

U701
Pin 1. 0
2. 0
3. 0
4. 0
5. 0.916
6. 1.82
7. 0.12
8. 10.89
Also I've found leaky 74VHC112 and 74AHC132. Is there any good replacement that available in the market? hard to find from my place.
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Old 24th January 2019, 10:37 AM   #13
Perry Babin is offline Perry Babin  United States
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
Leaky? Electrically?

Were they heating up?

If you have removed them, re-check the rail voltage. They could have been pulling down the reference used by the rail regulator circuit. I think pin 5 on U701 should be near 2.5v.
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Old 25th January 2019, 12:16 AM   #14
nonprof is offline nonprof
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by Perry Babin View Post
Leaky? Electrically?

Were they heating up?

If you have removed them, re-check the rail voltage. They could have been pulling down the reference used by the rail regulator circuit. I think pin 5 on U701 should be near 2.5v.
Yes, the logic gates/FF were about 30 ohms and 100 ohms on their power pins. The 3 pins nearby not sure it is regulator or transistor is heating so I removed the ICs and the heating went away.

Thank you Perry! I will replace the two ICs and let you know!
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