Did some further checking. After first turn-on I got the following:
LM317
In: 29.1V
Out: 14.5V
Adj: 13.4V
LM337
Out: -12.9V
In: -29.1V
Adj: -11.4V
Is there anything to learn from those numbers? I also noticed the solder joints look cold/cracked on the 317, and I'm getting a high frequency vibration from, I assume, the transformer when I first power it on. I didn't notice that before switching power supplies.
LM317
In: 29.1V
Out: 14.5V
Adj: 13.4V
LM337
Out: -12.9V
In: -29.1V
Adj: -11.4V
Is there anything to learn from those numbers? I also noticed the solder joints look cold/cracked on the 317, and I'm getting a high frequency vibration from, I assume, the transformer when I first power it on. I didn't notice that before switching power supplies.
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It's important that you post accurate numbers. The values for the 337 should all be negative.
High frequency vibration?
The values indicate that the regulators are a bit out of tolerance but it's not a big deal. For a healthy regulator the difference between out and adj will be 1.25v.
High frequency vibration?
The values indicate that the regulators are a bit out of tolerance but it's not a big deal. For a healthy regulator the difference between out and adj will be 1.25v.
Corrected, sorry.
Vibration, coil whine perhaps? Here's a 5 second video. It stops as soon as the amp fully powers up.
September 11, 2020 - YouTube
Vibration, coil whine perhaps? Here's a 5 second video. It stops as soon as the amp fully powers up.
September 11, 2020 - YouTube
Audio output from all channels still seems fine at low volume, and you're correct that the whine stops before the mute delay lifts. I reflowed the cracked looking solder joints on the regulators, and also some similar looking joints on the output fets. Still getting plenty of heat from the regulators. My measurements were slightly different, but that may have been my meter battery was dying.
M317
In: 28.5V
Out: 14.2V
Adj: 12.9V
LM337
Out: -12.5V
In: -28.5V
Adj: -11.1V
Hard to believe this could survive in a hot car environment. This was taken with about 77°F ambient with a light ceiling fan breeze
M317
In: 28.5V
Out: 14.2V
Adj: 12.9V
LM337
Out: -12.5V
In: -28.5V
Adj: -11.1V
Hard to believe this could survive in a hot car environment. This was taken with about 77°F ambient with a light ceiling fan breeze
Attachments
Yes, but I was getting similar readings off the back of the heatsink.
Q6, Q8, Q13 are definitely heating more than Q5, Q7, & Q12. About 125°F compared to about 100°F.
U202 is heating as much as 117°F give or take, and similarly U402 next to it. It's difficult to get accurate readings. The other TL072 chips are getting warm also, but these are the hottest as far as I can tell.
Q6, Q8, Q13 are definitely heating more than Q5, Q7, & Q12. About 125°F compared to about 100°F.
U202 is heating as much as 117°F give or take, and similarly U402 next to it. It's difficult to get accurate readings. The other TL072 chips are getting warm also, but these are the hottest as far as I can tell.
Are you saying that the 300 series transistors including Q309 are heating, alone or are all of the Qx09 transistors heating?
Post a photo of the drive signal on the gate legs of one PS FET in each bank when the FETs are heating unevenly and when they are heating equally.
For the hottest op-amp, remove it or at least lift it's power supply terminals and re-check the heating of the adjacent op-amp to see if it's still heating up.
Post a photo of the drive signal on the gate legs of one PS FET in each bank when the FETs are heating unevenly and when they are heating equally.
For the hottest op-amp, remove it or at least lift it's power supply terminals and re-check the heating of the adjacent op-amp to see if it's still heating up.
Q108, Q109
Q208, Q209
Q308, Q309
Q408, Q409
These are all heating, but maybe this is normal. Just trying to find any outliers that might indicate a problem. I don't have a scope, but I guess I need to get one if I'm going to try to figure this out without shipping it off to someone else.
I will try your suggestion of lifting the hottest op-amp. Thanks for your help, Perry
Q208, Q209
Q308, Q309
Q408, Q409
These are all heating, but maybe this is normal. Just trying to find any outliers that might indicate a problem. I don't have a scope, but I guess I need to get one if I'm going to try to figure this out without shipping it off to someone else.
I will try your suggestion of lifting the hottest op-amp. Thanks for your help, Perry
I lifted PIN 4 and PIN 8 of U402, TL072C. Before lifting those pins I was getting different readings on R43 and R44. I was getting about 40ohm on one and 37ohm on the other. With U402 PIN 4 & PIN 8 lifted they both read correctly at 20ohm.
Regulators are still heating to the same amounts as before. At 13.5V input I get:
LM317
In: 28.6V
Out: 14.2V
Adj: 12.9V
LM337
Out: -12.7V
In: -28.6V
Adj: -11.3V
Regulators are still heating to the same amounts as before. At 13.5V input I get:
LM317
In: 28.6V
Out: 14.2V
Adj: 12.9V
LM337
Out: -12.7V
In: -28.6V
Adj: -11.3V
Where is the LM833?
The voltage is well within what the op-amps can withstand. I don't remember TL072s getting hot but they can't all be bad.
Pick one of the hotter remaining ones and post the DC voltage on all of its terminals.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
The voltage is well within what the op-amps can withstand. I don't remember TL072s getting hot but they can't all be bad.
Pick one of the hotter remaining ones and post the DC voltage on all of its terminals.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
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