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361 Views 8 Replies 4 Participants Last post by  glankford
Audio express magazine (and I 'para-quote', to stay within forum rules).

Nov, 2002 issue, pg 68.

" Added the following very fruitful changes to my video system:

TV receiver (edit: As in, TV set!): I replaced the two filter capacitors for the 215 volt gun voltage with the largest capacitors which would physically fit in their locations. An oscilloscope check of this particular voltage showed several volts of unregulated wiggle, much reduced by the change...... amputated the AC cord near the set,and replaced it with a 'Corcom' branded 'filter in a box', and a beefy 16 guage 3 wire cord.

These changes improved color purity, balance,edge sharpness and detail, plus put more snap into the transient response. The set will now reproduce anything sent to it with the utmost appearance of faithfulness to the original signal."

?? Well, it's obvious when you think about it. The detail you are looking for, is modulated on TOP of the regulated signal, and by it, as stability in the tube systems actuation is controlled by the stability of that DC rail(s). DC tube rails are incredibly PARAMOUNT to getting the BEST out of your Projector. DC stability in these areas, across a very, very, very LARGE BANDWIDTH is critical to this endeavor, as projectors are multiple bandwidth sets, not fixed frequency. Since they are high voltage,and low current,the DC rail voltage is all Field strength,and not much in the way of 'mass' stability (current equals mass stability).


This is why power supply work and vibration control in tube amps is so freaking effective. Solid state amps are more immune (but not excepted!!) to this problem due to their high current mass, and lower voltage rails. But, on the other hand, they have NO finesse, because they can't change directions fast enough to accurately trace the leading edge of the signal, which is where the human ear works and does ALL--- I repeat ALL --- of it's work when interpreting the signal...

What works for the ear and tube amps.. does wonders for the transient edge and eye concerning video signals.

The syncronicity of the world is an amazing thing, you merely have to be paying a bit of attention. What exists in one science repeats itself exactly in another, you merely have to see how. There are universal rules of existence in operation that repeat themselves across almost every kind of layer of human related existence and science, you merely have to train yourself to see them.


To repair this, all you can do, is upgrade the quality and quantity of the capacitance, so it has large bandwidth, with low impedance. This is 'back EMF' coupled, in terms of 'light speed (80% or so, maybe a hair better) to the rail itself. This is why you need to put the 'buffering' caps as close to the tube itself as is possible. This happens to be......>> the good ole' neckboard.

Possible problems are:

1) excessive capacitance causing DC power supply failure at turn on either immediately, or lets say, a year down the road.

2) Over-voltage of the rail and tube failure (too close to spec on over powered tube (low odds, but mentioned as a possibility). basically, rail voltage floating too high. if this happens,then the power supply is REALLY under built!! and the capacitance is SORELY needed!

3) Oscillation of the system, due to interaction between the main power supply and the signal modulating the power supply, due to a 'Helmholtz' kind of resonance between the regular power supply and the extra capacitance, which is located away from the main power supply. The wiring itself facilitates this problem, due to it's inherent impedance. It is a possibility, due to the fact that the Projector is a multi-frequency device.

In my experience, NONE of the above have ever happened.

Rise and settling times of ALL VGA and video signals in the analog domain are all over the freaking place. This means that large bandwidth Power supply stability is critical. Low ripple, and low Z across a large bandwidth, in terms of PS stability and transient draw capacity is critical.

Trust me,as STOCK PJ DOESN'T have it. t has it better than an lowly Direct view CRT, but not really. It has been engineered to be better, but if you open those PJ's up---- 99.99999% of the time, you could find something substantially better to put in there!

Break out your PJ schematics today!
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Hmmmmm..... mechanically damped PJ chassis'? Who'da thunk it!
Thanks Ken,

that was better than caffein...
So...the obvious conlusion is,after a bit of applied logic..is that DC power rail stabilty is exactly.... dimensionality of image, color purity, detail, signal to noise ratio, and dynamic range.

One small component of what can make a PJ look better. Or make amplifiers sound better. etc, etc, etc. same-same. no differnce.

Almost every-single- audiophile related phenomenon of cause related effect, is effective across the board in CRT projectors as well. Hell, most apply to Digital projectors too...

Move your freaking brain... kick it square in it's ass end today. The more often you do it, the more you will grow, and the better you will get at it.

This is the simple stuff. Come on! Get with the program!

edit: you snuck one (post) in there, on me, Mike! Are we having fun yet!
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yes, and I agree with most of what you've said here, and I also use the same approach. It's just that you're very good at saying the same thing so many different ways :)
I understand about 20% of that and know some very basic electronics. So running a power conditioner might do no good because the problem lyes within the pj itself? Tube pj's? :confused:
I agree in principle, but many of the video circuits in the projectors out there have their own regulation (at the board level). That way any power supply fluctuation would not be noticed at that board. Only if the power supply rail dipped below regulation voltage at that board would you see a problem. That said, the caps in the power supply are important, BUT don't forget any filter caps at the video signal processing level.

It's all about bandwith within a lo-Z, reserve,and transient behaviour in a PS situation, and regulators simply aren't fast enough.... capacitors are much more stable in many important ways. The capacitor's behaivor can stabilize output in crucial ways. Waveform vs distortion shaping, over a large bandwith, etc. Because of the speeds involved, waveform stability over large bandwitdhs are crucial in video circuits. Many regualted supplies are inadeqaute AFTER the regulator. Fix it THERE. Right at the circuit in question.

It's 'nodal' PS design. 'Nodal' buffering. Works every time.

I was just bored, and decided to post something.

Besides, it's a full moon....
Fair enough. It has been a while since I have actually used my BSEE. I didn't account for regulator response time (bandwidth). The real trick would be to dust off my oscilloscope and start probing around my barco for ripple and coupled noise.

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