Well,
This brings up another issue, what is the wiring to and between the caps?
How many ufd are the caps?
It is possible that the wire is not heavy enough, or the traces, whatever you are using.
You should test the rails themselves, as mentioned.
I'm still completely lost on what you need a thermistor for if you use a slow start in the primary?? Lost on what a relay is doing in the secondary at all. Lost on what effect a barrier strip will have, removed or not. IF there was a problem with radiation from wiring or a barrier strip, then shielding would be indicated, but I doubt that this is where the problem comes from.
The MUR diodes are soft recovery, iirc...
...and davada, I am unclear on why the caps are causing this noise, I use far more capacitance than he does in my Symphony No.1 amplifiers and I don't get that noise. However I do use copper buss bar and 10ga. wire. (mine is a total of ~500,000ufd. @ ~55vdc)
BigE, it's current, not voltage. Charging up big caps take big current on each cycle, so think big spikes of current, not voltage. So Vdrop on ur wiring = switching noise on ur rails.
The hard ground I refer to, and I should have been clear is the chassis ground vs. the signal ground.
Otoh, you might want to also check for ground loops by lifting the chassis safety ground at the outlet ("3 prong ground lift adapter). Probably nothing there to be discovered, but maybe.
Somewhere in there something you have done is amiss. A picture might really show it (or not).
I would have suggested an old school Tektronix over a new fangled digital scope, unless it was a high-end new fangled digital scope. Fwiw. I do not like the aliasing in the display on the ones I have seen thus far.
_-_-
This brings up another issue, what is the wiring to and between the caps?
How many ufd are the caps?
It is possible that the wire is not heavy enough, or the traces, whatever you are using.
You should test the rails themselves, as mentioned.
I'm still completely lost on what you need a thermistor for if you use a slow start in the primary?? Lost on what a relay is doing in the secondary at all. Lost on what effect a barrier strip will have, removed or not. IF there was a problem with radiation from wiring or a barrier strip, then shielding would be indicated, but I doubt that this is where the problem comes from.
The MUR diodes are soft recovery, iirc...
...and davada, I am unclear on why the caps are causing this noise, I use far more capacitance than he does in my Symphony No.1 amplifiers and I don't get that noise. However I do use copper buss bar and 10ga. wire. (mine is a total of ~500,000ufd. @ ~55vdc)
BigE, it's current, not voltage. Charging up big caps take big current on each cycle, so think big spikes of current, not voltage. So Vdrop on ur wiring = switching noise on ur rails.
The hard ground I refer to, and I should have been clear is the chassis ground vs. the signal ground.
Otoh, you might want to also check for ground loops by lifting the chassis safety ground at the outlet ("3 prong ground lift adapter). Probably nothing there to be discovered, but maybe.
Somewhere in there something you have done is amiss. A picture might really show it (or not).
I would have suggested an old school Tektronix over a new fangled digital scope, unless it was a high-end new fangled digital scope. Fwiw. I do not like the aliasing in the display on the ones I have seen thus far.
_-_-
How does that work? I really don't understand that.
if you remove the filter caps all the switching noise goes away..
The switching noise is proportional to the value of capacitance.
Consider the instantaneous current at peak sine and the fact that a capacitor is essentially a short circuit to the rectifiers. The rectifiers have some resistance and a voltage drop. So the switching noise increases with instantaneous current. The caps at 80000uF are far too slow to absorb RF.
The caps are mounted on Tea Bag's PS board. The traces on the board are more like ground planes and have minimal distance between them.... ie no loop area. I believe that Tea Bag used 4oz copper.
The caps are 22,000 uF each arranged as CRC so that each C is 44,000 uF
Each channel has 8 of them.
bear said:
A slow/soft start operates very quickly. The cap bank takes much longer to come up to voltage, and will draw extreme amounts of current for a longer duration. A thermistor and a bypass relay is a common implementation for a slow *charge* circuit. A soft start does nothing for the cap bank inrush current.
Hence, the thermistor, bypass relay and blocking relay to ensure that the thermistor is cool enough to work properly.
bear said:
OK. The chassis is connected to the IEC safety earth with a 2-3" piece of wire.
bear said:
Sorry, that is something I will not do.
bear said:
I've misplaced my camera, I think it is about 2hrs away.
I have posted some earlier shots on the F5T build thread. Shots at 3715/3716
http://www.diyaudio.com/forums/pass-labs/207103-f5-turbo-builders-thread-372.html
My 2 centimes here -- I would remove everything relating to the 50/60Hz issue from this thread as it really doesn't relate to the QA400 itself, but an idiosyncratic issue for the user.
It's just putting tons of chaff into the thread into what is, otherwise, a discussion of an otherwise very fine instrument.
It's just putting tons of chaff into the thread into what is, otherwise, a discussion of an otherwise very fine instrument.
At the moment I have no use for one but I may later.
Since BigE has a Canadian flag I thought maybe QA had changed there policy.
