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More info?)
Jeff,
I wrote this up a week ago on another post regarding a vector monitor
cap kit. Figured I would paste it here. The commentary is centered
around a vector monitor, but applies to just about any circuit.
"Do not install way overrated capacitors as far as working voltage is
concerned. Not only is it pointless and not very cost efficient but you
will actually degrade performance of the circuit if you go too high.
One step up is a good rule of thumb if you simply must do it.
I believe most people do this thinking they will gain some sort of
logevity by running overkill on the cap voltages, Let me be very clear
when I say this is a true deal, but a very misleading theory. By going
way overkill on the working voltage you lower the capicitors working
efficiency in the circuit. Therefor you do gain in longevity because
the biggest cap killer will be heat fluctuation overt time (things
start to vent, rubber starts to crack, it dries up). BY going way
overkill you reduce the capacitors workload by reducing it's efficiency
in the circuit; if your following. Thus they will last longer. But is
this correct for your circuit topology? Not really.
To reduce heat wear properly, simply choose a cap with a higher temp
rating. You will have several to shoose from as I'm sure you know. Get
85 Degree centigrade or higher if available and if you must go ONE step
higher on working voltage and not a penny higher.
Onto farad ratings. My rules:
1: If the cap is being used in PARALELL with a POWER SUPPLY, the higher
the rating the better. HOWEVER I try and go no further then doubling as
the cap has become a load when in charge state and going too high can
reduce the power supply performance and any regulation/recovery
circuitry can be affected. However by going as high as doubling on the
farad rating you achieve greater line ripple rejection and that NEVER
hurts.
2: When a capacitor is in PARALELL in a circuit OTHER THEN A POWER
SUPPLY it is a good idea to not deviate from its value without having a
good knowledge of the topology of the design. For example in a
regulation system, and amplifier section, or a switching power supply
utilizing a transformer (Ie, your deflection board (amp) your HV unit
(Switching PS using a trans.) and regulation system (Your LV section on
the deflection boards) --- Deviating from these values in farads or
working voltage can cause anything from circuit performance you can
only see with a scope all the way down to catastrophic failure of the
circuit over time or failure to operate entirely. Capacitors used in
this fashion are generally parts of a frequency related circuit. By
altering them you alter the operation of the entire circuit and the
frequency it was designed to operate at. In your monitor it can cause
something as simple as reduced or increased modulation in the amplifier
section of the deflection board, total failure, unwanted oscillation,
etc. In the HV section changing the pulse rate to the flyback windings
can cause total failure of the part or function. Ie. if you are pulsing
the flyback @ X freq and getting 12 kv, then decide to triple a cap
rating that can alter the freq to Y can change the flyback output to
1/3 the current and 3 times the voltage. The number are not exact and
for example purposes ONLY to show vague example only!
3: Capacitors used in series - same deal as #2
This concludes my views on cap upgrades, I hope someone finds it of
use. Best bet is to stick to design ratings unless you are dealing with
paralell PS caps. Overall it is good to get the lowest ESR ratings and
highest temp. ratings for the best performance and longest life of a
cap in a circuit.
Another misconception I will address is the usage of the higher rated
transistors being installed as an "upgrade" for these monitors. They
are of a MUCH higher voltage supply rating. How this performs some
significant longevity gain in a LOW impeadence amplifier design stifles
me. For a true upgrade install a transistor with similar or higher
voltage ratings, but looks for a significant increase in the current
ratins as well. In a low impeadence amplifier with a low voltage supply
you will benifit far more in stability, temp coefficients and longevity
this way. Those trannies still get hot even though they have IIRC three
times the voltage ratings because they are being used in a low supply
low impeadence modified class a/b amplifier design. Nice choice, wrong
choice. Wait until I get bored and wire up my car amplifier to run a
6100 deflection system. I'll be sure and post pics. Thats all the
deflection system is afterall; a stereo amplifier with a regulated
power supply. The spot kill circuitry is nothing more then the same
archaic protection you see is old amplifiers with the exception being
the incorporation of a "idiot light". Imaging if the creators of
aftermarket deflection boards were intelligent?They now have low
impeadence, 100wpch SINGLE class D amplifier solutions. So a small (how
does 4" by 4" strike you?) PCB with a few small compoenets could take
the place of the WG6100 deflection boards and drive the whole 9 yards
with a increase in efficiency of over 30% and 30% LESS BTU's? How about
a third the cost to manufacture and sell? How about I accuse all of
them of living in the dark and cashing in on a inferior, barely
redesigned product that is way overbloated and way over costly? Sad but
true.
Onto the rest of the stuff. Just replace it with the manufacture
suggested parts and don't go and change any resistor values in any
section unless you know what you are ultimatly doing and you will
increase/decrease overall gain of the circuit if you do the wrong
thing. "
Hope that helps
- Matt
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