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Counterpoint 5.1- Beyond My Comprehension

I just experienced good news a moment ago- my Counterpoint 5.1 preamp is again operating properly. I had experienced greatly diminished volume in my system. This happened suddenly- when I powered everything up an placed an LP on the table, it was barley audible. All other selections were lower also.

To make a long story of tube swapping, amp swapping and speaker swapping short, I replaced the CA4 in the power supply and all is well. It appeared to have a smoky band around the center of the tube.

Does anyone know why this caused a reduction in volume instead of a total loss of volume?

Thanks in advance!
mknowles16
dynami28
55 posts
 
If I remember correctly, tubes do not stop working unless they are cracked/broken or somehow lose their vacuum. But the burnt band you described is going to cause diminished performance, thus your lowered, but not total, loss of sound.

I'm not 100 percent sure if I'm right, its been a while since I've messed around with tubes. But I hope I helped anyway,

Andrew
Synesthesia Studios
hifigeek1
770 posts
 
If that tube is used as a voltage reference or as a voltage regulator and the voltage was low, that could potentially cause a loss in gain. I'm just guessing at this point. The dark band/ring around the center of the plate of the tube usually indicates the tube is worn out or damaged.
johnsonwu
410 posts
 
The 6CA4 inthe SA5.1 is the rectifier (note: not regulator) for the high voltage B+ of the SA5.1.
It converts AC to some 500V of DC that goes into the regulator.
If the B+ going into the regulator has low voltage, then obviously gain will be diminished.
Glad you didnt damage the regulator by replacing the 6CA4 quick.
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