|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
74.37.227.139
In Reply to: Re: question for Eli... posted by Vinnie on April 30, 2007 at 03:42:02:
Vinnie, exactly what is connected to the end of the supply? I understand there's an L and a C, but what's after that? An amplifier? A big power resistor? What?Also, are the heaters of the 6au4's also powered by the variac, or are they powered by a separate 6V transformer that's not plugged into the variac?
Follow Ups:
Dave
I have the front end module of the amplifier hooked up to the old psu module with the hybrid bridge and one of the two chokes and the capacitors standing along side.
The 6au4 filaments are powered by a separate tranny that is also brought up by the variac.
I actually got music out the other end before the fuse blew at about 850 vdc. It's running the actual load.
It's possible that the current comes on all of a sudden because the 6au4 heaters need to get up to a certain voltage before they start to work. I suggest plugging the heater supply in to a separate output (actually, all of the heaters/filaments) and let them warm up for a minute before you start turning up the variac. Odds are, you'll see different behavior.The 3 amps is on the primary side of the big power transformer. Is this the 1450V unit that you mentioned before? That's a turns ratio of something like 1:12, which means that the secondary is delivering something like 3/12 = 250mA. If it's a stereo amp, that's not a lot for 845's. Could be your variac is blowing fuses because it's just not up to the task (assuming the fuse is in the variac.) If it's a monoblock then it might be a lot, especially since you are not up to full operating voltage yet. If that's the case then I would look for a problem somewhere. Is this an amp that you had running good before with a different power supply? What kind of B+ voltage and idle current were you seeing then?
-- Dave
Yes to both. This is the amp that was running good before and it had about 750 vdc for B+ then, not sure about the about the idle current, but the bias was set at about -115vdc. And yes, this is the 1450 volt tranny.
I think it's more likely to be the 6au4's as they were not on the old amp and if I am reading the tube manual correctly they draw a lot of juice. I hope your guess about them conducting all at once is not the problem, because I am using them to eliminate power spikes with their slow warm up.
Vince,Mr. Cigna told you what needs to be done. The 6AU4s' filament trafo should NOT be on the variac. If you let the heaters warm up before you turn the applied voltage up, the surge should be SMALLER.
Until the heater voltage becomes a reasonable fraction of nominal, cathode emission is ABNORMALLY small. It's like a switch across a resistor was thrown. More current flows.
Eli D.
Eli
Please see above posts about calcs and see if my last post to triode is on the right track.
Thanks!
Vince
This post is made possible by the generous support of people like you and our sponsors: