Attached is the B+ supply for Cary Audio's SLP-90. It is als0 somewhat similar to subsequent model SLP-94, SLP-98..
The strange thing is the rectifier feeds into extremely brutal CRCRC stage (560uF-22k-560uF-22k). If i run this in PSUD, it gets all sorts of red flags, including high current, high PIV etc.
But the preamp seems to be running well and there is no complain about premature rectifier life.
What seems to be the trick here?
The strange thing is the rectifier feeds into extremely brutal CRCRC stage (560uF-22k-560uF-22k). If i run this in PSUD, it gets all sorts of red flags, including high current, high PIV etc.
But the preamp seems to be running well and there is no complain about premature rectifier life.
What seems to be the trick here?
Attachments
A 560uF capacitor as the first capacitor in the power supply? A little bit tough for the rectifier tubes?
Carey is (sadly) quite notorious for badly abusing vacuum rectifiers in their designs. 😡
Apparently, Carey had a large on hand supply of those 560 μF. parts and made use of them, "come Hell or high water".
Perhaps they were able to source vacuum rectifiers that far exceeded the spec's, for several types.
If you want good service life from vacuum rectifiers, be very respectful of published limits. For a single 6CA4/EZ81, 47 μF. is "correct", in the 1st PSU filter position. A DC link part here will maximize performance. Follow with a decent choke and the remainder of the PSU filter is "decoupled" from rectifier and 1st filter capacitor.
Apparently, Carey had a large on hand supply of those 560 μF. parts and made use of them, "come Hell or high water".
Perhaps they were able to source vacuum rectifiers that far exceeded the spec's, for several types.
If you want good service life from vacuum rectifiers, be very respectful of published limits. For a single 6CA4/EZ81, 47 μF. is "correct", in the 1st PSU filter position. A DC link part here will maximize performance. Follow with a decent choke and the remainder of the PSU filter is "decoupled" from rectifier and 1st filter capacitor.
Normally when overload the tube will momentarily glow too much during turn on, but i don't see this symptom in this preamp. My friend who own these unit don't have issue with the lifespan of the rectifier, also the same design has been used continuously for >10 years production run.
So I don't think it is an issue even though it goes against the spec. But really wondering about the discrepancy. Maybe using the standby switch helps?
So I don't think it is an issue even though it goes against the spec. But really wondering about the discrepancy. Maybe using the standby switch helps?
skyraider, that is probably because the power traffo secondary has high dc resistance windings.....
if you can please measure the dc resistances of primary and secondary windings so we can have a better clue....
if you can please measure the dc resistances of primary and secondary windings so we can have a better clue....