Tube Linear Amplifier HV Electrolytic Capacitor Banks explained

Since I am currently going thru and recapping a Blackcat JB-2000 and since both here and on Facebook there were some questions about and misinformation about HV capacitor banks, I thought I could kill 2 birds with one stone. This vid is a walkthru and simplified explanation of Tube HV capacitance and capacitor banks only. The capacitance is only a part of the complete HV power supply but I am not addressing the rest of the chain on this one, just the capacitance.
With tube amplifiers, or just any tube in general, Tubes run on high voltage and amplfy or alter voltage. BTW, transistors need voltage, but transistors generally use low voltage and transistors 'generally' amplify or alter current. All things equal, voltage amplification has even harmonics and sounds good to the ear and transistors which amplify current which has odd harmonics which does not sound good to the ear. In hi-fidelity audio, they often use special circuits and techniques to tame that bad 'transistor' sound.
A sweep tube like a 6lf6 or 6lq6 used in sweep tube amplifiers generally run on 700-1000v's. Transmitting tube amps, for amateur radio use, generally run on 2000-5000v's. Generally, for capacitance, you want to have 30uf's for every amp drawn. There are other factors, like mode of operation, but 30uf's per amp is a good rule of thumb.
Since the JB-2000 in the vid runs around 2700v and around 1 amp, it would need a capacitor or capacitor bank rated at around 3000 volts for a safety margin with voltage and around 30uf's or capacitance. With voltage, there is no shortcuts. You undervolt the cap bank and you are asking for trouble. With UF's, it's not a good idea to go under, but in general its not dangerous to do so. So the bank in the JB-2000 has 6 450v caps at 100uf's. That would be a total of 2700v and 16uf's. Hence, it's undersized for both voltage and uf rating. It has replacement caps going in at 500v at 220uf's per cap. Hence, the new caps will give a total of 3000v at 36uf's.
With the voltage, with caps in series, the voltage adds or multiplies but the UF rating divides. More caps = less UF's. There is a lot of misconception about that, but still, it's a fact. Caps in series multiply the voltage per cap. 3 in series, the voltage multiplies x3. Ten caps in series, the voltage multiplies x10. To repeat, it divides per cap when it comes to the UF's. With 2 caps, the UF's divide by 2. With 12, the UF's divide by 12.
As you add more caps in series, it's also more and more important to have good equalizing resistors across each of the caps. The equalizing resistors ensure each cap gets the same or 'equal' voltage across it. Also, those equalizing caps perform double duty as they also perform the function of bleeding down the caps so the caps won't hold a charge. Good caps can hold a charge for a year unpowered if it has no bleed. Heck, when I was young, I got hit by an arcade monitor that had been off for a month. It was at the Greyhound bus station here in Detroit. I screamed out when it bit me. I thought everyone would be looking at me and I would be embarrassed, but of course, nobody paid me any attention.
In conclusion, go over 20% or more for the voltage, use at least 25uf's per amp, and with the UF's, more up to a certain point is generally good, but don't go crazy with it. 1000uf's would run great, but if it arcs KAPOW or even with dealing with the surge of that during turn-on would be problematic. Must run equalizing resistors which also perform double duty as bleeders. Old days, they favored heavy eq and heavy bleed, but modern thinking is to go lighter.

[@keithweiss7899]

I’m a retired electronics teacher. You did a good job Doc.😊

[@markbarnhill6300]

really like the way you explain circuits! Very easy to understand.

[@bblod4896]

Nice. Thanks for the lecture Doc.

[@thesquirrelchroniclesakare7808]

Great explanation Doc 💪🏻

[@MM0IMC]

My old GS-35b homebrewed 10m linear amplifier used to use 10 x 220uf 450V in the original capacitor bank. This lasted over 4 years at 3.4kV @ 1Amp.
I recently replaced the capacitor board and changed the caps to 10 x 330uF 450V. Thats more than enough headroom. Also the capacitor bank helps smooth out the DC, so that you don't get AC hum.

[@brianbooth-ii7ct]

Great info doc

[@williamcaspers5252]

That oil filled cap is equivalent to what was used in older defibrillators and must be handled with respect.

[@RogerSedore]

You've got a fair bit of work to get done to get back to retirement. Lol

[@187RedFalcon]

233 mavrick

[@JustinRuth-km4wz]

That reciver needs work

[@321CatboxWA]

When you got the biggest hammer, you can have any kinda audio .