What to do with 3500uF 650V caps???

[SGregory]

I was given 4 3500uF 650V power caps from a DC power drive. Caps look good and were working prior to dis-assembly. The are of BEH manufacture.

I was thinking it would be good for a power supply for a SE 300 type amp. Probably way over kill, but isn't that wht DIY is about.

My concern is charging these beasts without burning up the tranny or rectifier. Any thoughts?

Scott

[wicked1]

Im certainly not the expert, but I think that's too big for a tube rectifier to handle. For tube circuits, people generally stay in the hundreds of uf, not thousands. Maybe it would work w/ SS rectifier, but Im not sure.
I've seen cathode bypass caps are that large, but I guess then you don't need that voltage.. hmmm

[Richard Ellis]

Just ran a sim.&..............
Assuming a TX of 360-0-360, IN4007 Full-wave, 200mA constant current load,
With a 5 Henrie choke and your Big-un 3500uF cap.
The transformer spike ran up to appx 2.5 amps within one second...but settled down after one sec.
The load voltage ran at.....ready for this?...
310.0525 low, to a high of 310.334 volts DC......smooth.
Now to put a thermistor in to limit the current spike.!!
__________________________________________________ _Rick.........

[SGregory]

A couple of my co-workers know my hobby and gave me the stuff. I figured that they were not that useful for tubes, but they are massive and certainly would look good ;-)
I have built alot of SS stuff, and am starting to get into the idea of building tubes stuff.

I played with PSUD and it said pretty much the same thing, that a tube rectifier woldn't work. The other problem I saw is that if used, it would be an unpleasant experience to get shocked.

Maybe i'll use them to build a rail gun :-o

[pedroskova]

What to do with 3500uF 650V caps???

Build an arc welder?

[aardvarkash10]

wooohoo! My stepbrother the e-waste recycler just donated a dozen 40uf 400V caps and four 2200uf 350V caps! What a dilemma... Just simmed the big ones in a 370-0-370 TX supply for my next project. Using all four in a CRC chain (paralleled caps to cover the voltage requirement) I can get just over 400VDC @ 200ma with less than 0.01V ripple. No choke, no joke. Ahhh, 15 second rise time. Self soft-start!

[tubelab.com]

The tube rectifier is out of the question. You can use them with 11 amp 1200 volt FREDS or Fairchild Steath diodes. The power transformer will groan big time when you flip the switch, so you need an inrush current limiter.

I got some 1600 uF 450 volt caps on Ebay a few years ago that are about the size of a Fosters beer can. I used them with FRED diodes on the 240 volt secondary of a 500 watt industrial control transformer. I got about 325 volts of B+. I ran two of these setups in series with a variac on the input to make a 0 to 800 volt power supply. The variac goes to 145 volts on the input.

Diagram at the bottom of this page:

http://www.tubelab.com/PowerSupplies.htm

WARNING!!!!!! there is a serious amount of stored energy capability here. A mistake can kill you or blow things up in a big way. Don't even think about this unless you know what you are doing!

[Miles Prower]

Originally Posted by SGregory

I was given 4 3500uF 650V power caps from a DC power drive. Caps look good and were working prior to dis-assembly. The are of BEH manufacture.

I was thinking it would be good for a power supply for a SE 300 type amp. Probably way over kill, but isn't that wht DIY is about.

My concern is charging these beasts without burning up the tranny or rectifier. Any thoughts?

Something like that would be terrific for an amp that uses these new SiC JFETs. These need to be run at some serious voltages in order to get the Crt down to reasonable levels, and to hit the linear part of the Crt / Vds characteristic. Being that these are still solid state, they will pull bigger currents than most VTs, and big, high voltage filter capacitors would come in handy.

Your best bet would probably be an industrial control xfmr with a generous VA rating to handle the resulting Isurge. Classic and vintage hollow state power xfmrs will probably roll over and die, even if the Si diodes won't complain.

[SGregory]

Thanks George and Miles,
WAF would be way low with a GE Control Transformer in the living room.
I felt blessed that she okayed me building a couple of tube amps this winter despite not having all of the kitchen cabinets built yet. (This house has been a 4 yr project and she said I needed a break). I think I'll put these back in the box and wait. I also don't want to re-rewire the house yet.

Maybe I'll build a couple tubelab amps with normal capacitors :-) Sent you an email George.

And yes that would be ALOT of stored energy to have in a residential setting. Something the cats would not like. Seriously though in industry these things go in rated cabinets to contain failures. Another issue for WAF.

[Nige64]

could use them as part of a choke input type of filter for your psu, could use ss or tubes then. makes great soft start too.