The 1N5408 negative rail clamp is a good idea but JI vehemently opposed
that idea every time I suggested it and claims the 1N4007 is better.
Unfortunately Ive had his "expertly designed" amps in here several times for
service with vaporized 1N4007's when a direct short is what they were
supposed to do.
## A single 1N4007 is the wrong diode for the job. It's only a 30A surge
rated device.
The 1N5408 has a 200A surge rating. The 6A10 has a 400A surge rating. I use
2-4 x
6A10's , all in parallel, all pointed the same way. Then no more replacing
safety diodes.
Use 6A10's across the meter's as well.
## I install a HV fuse just inboard of the 50 ohm, 50 watt glitch resistor.
The 50 ohm glitch R
will LIMIT the peak fault current to a safe value. The HV fuse will
INTERRUPT the fault
current, and do so in < 2 msecs. All that fault current has to pass through
the safety diode
installed between chassis and B- rail.
Thanks to KM1H and K0UYA for the advice. The form factor of the stock
> caps for the Titan is the killer: very long and very narrow compared to
> the "usual" for this capacity and voltage. I'm confident I could make a
> safe outboard "capacitor box" bolted to the side of the current PS to
> allow more available/affordable capacitors, but I have to weigh all the
> factors, and $29 each at Newark may be a better choice. I don't know if
> 270uf/8 is sufficient vs 400uf/8 for an amp that can put out 1.5kw with
> the figurative pinky finger of one hand. So I'm sure I want to stay with
> 400uf per capacitor, while also paying close attention to temperature
> and rated life specs, ESR, etc. This is why I asked about a better deal
> for *the specific Mallory (CD) capacitors* before exploring unknown
> territory.
### No big deal using an outboard cap box. I have done just that several
times.
I have case-loads of 2300 uf @ 450 vdc lytics, all with 10-32 screw terminals.
I put a 100 k- 3 watt mof across each cap. [1% tol, mouser item]. With 8-12
x caps in series, you end up with loads of uf...like 230 uf with 10 x
caps....and
also a healthy 4.5 kv rating. The resulting dynamic regulation on ssb/cw is
nothing short
of phenomenal. Ripple is reduced to essentially zero. Your pep output on the
wattmeter
will increase a bit.
## with any B+ to chassis arc...or B+ to grnded grid arc, still no big
issue. The peak fault
current is the same, regardless of how much uf you have in the HV supply.
Peak fault
current is just B+ / glitch resistor value. 3kv/50 ohms = 60 amps fault
current.
60A fault current through the B+ hv fuse [ rated at 1 A or whatever u require
for normal
operation] will blow open the hv fuse asap.
## the HV step star is no big deal either. I used a 10-20 ohm metal cased
arcol type
resistor in one leg of the 240 vac line. It gets shunted out after a 5-10
secs. I built a separate
step start box, consisting of a 30A DPST relay to apply the 240 vac. And also
a 30A SPST
2nd relay, that shunts the step start resistor. You can either use a 0-10 sec
timer to activate the
step start spst relay...OR... just use 2 x separate toggle switchs.... one for
each relay.
## If you require any HV caps, I have caseloads of em, new, $12.00 per cap.
2.5" diam x 4" long,
14 oz each. ESR is .026 ohm Ripple current rating is 10 A CCS. We use
the same caps in everything
from 3-500Z amps up to 15 kw amps. They come with the 10-32 machine screws +
internal tooth lockwashers.
If you need the 100 k 3 watt mof's [ these measure at .2% tol] I have those
too.
later.... Jim VE7RF
>
> The Digikey price for these caps is $46 each, if they had them in stock,
> which they don't. Mouser does have 15 in stock at $81 each. Other
> suppliers I've found all over the planet have prices around $35 or more.
>
> Anyway, I wanted to make sure there isn't a golden supplier hiding out.
>
> Regards,
> Pete AD4L
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