Wiring series cap cans

[Ed_Chambley]

I need to put a dual cap can 100uf/475v in series for 50uf/950v.  I am not sure of the method in using a cap can with only one negative post.  Never done this.  Usually I use from Doug's library, but on this build I am using cans.  Confusing me is the one negative.  Anyone have a drawing or description.

Thanks

[Willabe]

I need to put a dual cap can 100uf/475v in series for 50uf/950v. 
Confusing me is the one negative. 

Hi Ed,

You can't do it because like you've pointed out, only 1 negative lead connection.


              Brad     

[phsyconoodler]

Sure you can!But you need two cans to do it.

[jjasilli]

Yes, but as willabe says, caps within the same can cannot be put in series with one another.  If connected together, caps in the same can, can be wired only in parallel.  One solution is to put a separate cap in series with a cap in the can. 

If you put a can in series with another can, then the metal body of "top" can needs to be isolated from the chassis, or it will short out.  Also, the metal body of the top can will be LIVE.  In the old days the solution to this was a cardboard housing.  My solution is to double dip a metal can in Plasticoat.

[Ed_Chambley]

Yes, but as willabe says, caps within the same can cannot be put in series with one another.  If connected together, caps in the same can, can be wired only in parallel.  One solution is to put a separate cap in series with a cap in the can.  

If you put a can in series with another can, then the metal body of "top" can needs to be isolated from the chassis, or it will short out.  Also, the metal body of the top can will be LIVE.  In the old days the solution to this was a cardboard housing.  My solution is to double dip a metal can in Plasticoat.

I can put another in series with the can.  In the library and on the schematic a 220k balance resistor is used, but I have seen different values.  I have a 100uf/475v axial i can use.  What determines the resistor values?  I attached a schematic, but the voltage will be higher due to SS rectification and the cap cans I have are rated at 500v.  Would it be best to forgo the can in favor of 4 axial, 2 pairs in series connected by the 3-10c choke?

[Glennjeff]

Not sure if this is helpful.

100W solid state rectified Ceriatone Humble Rabbit Man Clone PS Filter caps and resistors.


https://imageshack.us/a/img515/2410/hrm100wpscaps.jpg



https://imageshack.us/a/img16/9706/hrmcaps.jpg

QUESTION.
How do you get that reference line under photos that gives number of views, size and when you click it ask if you want to save or open?

[sluckey]

What determines the resistor values?  I attached a schematic, but the voltage will be higher due to SS rectification and the cap cans I have are rated at 500v.  Would it be best to forgo the can in favor of 4 axial, 2 pairs in series connected by the 3-10c choke?

You determine the resistor values. 220K is typical, gets the job done, and does not put much additional load on the power supply. I would abandon the cap can idea and use all axial or 'snap in' caps. You really need to do this for all four filter caps in that circuit, not just the ones connected to the choke. Speaking of choke, notice that the plate current also flows thru that 3-10C choke? You will need a high current choke. Triode USA has a replacement choke for $17.00. Triode also has a cap farm board to replace all the filter caps in that amp. Take a look. Even if you don't buy their board you may get some ideas.

choke........  http://www.triodeelectronics.com/c354.html
cap board...  http://www.triodeelectronics.com/sdslabmk3cap1.html

So, are you building a 200S? You know the 200S is a bass amp, right? If you really want a guitar amp instead, take a look at the 100S. It's identical to the 200S, except the tone stack is designed for guitar, rather than bass.

[Ed_Chambley]

What determines the resistor values?  I attached a schematic, but the voltage will be higher due to SS rectification and the cap cans I have are rated at 500v.  Would it be best to forgo the can in favor of 4 axial, 2 pairs in series connected by the 3-10c choke?

You determine the resistor values. 220K is typical, gets the job done, and does not put much additional load on the power supply. I would abandon the cap can idea and use all axial or 'snap in' caps. You really need to do this for all four filter caps in that circuit, not just the ones connected to the choke. Speaking of choke, notice that the plate current also flows thru that 3-10C choke? You will need a high current choke. Triode USA has a replacement choke for $17.00. Triode also has a cap farm board to replace all the filter caps in that amp. Take a look. Even if you don't buy their board you may get some ideas.

choke........  http://www.triodeelectronics.com/c354.html
cap board...  http://www.triodeelectronics.com/sdslabmk3cap1.html

So, are you building a 200S? You know the 200S is a bass amp, right? If you really want a guitar amp instead, take a look at the 100S. It's identical to the 200S, except the tone stack is designed for guitar, rather than bass.

I am restoring one.  Filter caps are trash.  I have ordered the choke from Triode.  I keep getting sidetracked with "repairs".  I was thinking I could just build a doghouse like a Super Reverb.  The voltage would be covered and I have room on the chassis.  Since you suggest the cans, I will look further.

[sluckey]

Since you suggest the cans

I suggested abandoning the cap can idea.

When I restored my Sceptre, I used a couple Sprague Atom 20µF@600V axial caps and a quad can rated at 525V. I found out about the cap boards from Triode after the fact. At that time, the cap board was only $40. The board would have been cheaper and neater! No way would I pay $66 for that board today for my own amp.

[Ed_Chambley]

Since you suggest the cans

I suggested abandoning the cap can idea.

When I restored my Sceptre, I used a couple Sprague Atom 20µF@600V axial caps and a quad can rated at 525V. I found out about the cap boards from Triode after the fact. At that time, the cap board was only $40. The board would have been cheaper and neater! No way would I pay $66 for that board today for my own amp.

Understood and SOLD.  I will check as I probably have the caps on-hand.  Why would you think SUNN would use a 525v cap with an initial B+ just over 500v anyway?  I attempted to reform the original cap, but not happening.

I do really like the board from Triode as it is neat, but if I already have the parts it does not make good financial sense.

[sluckey]

Why would you think SUNN would use a 525v cap with an initial B+ just over 500v anyway?

Sunn just copied the Dynaco Mark III. The 525V rating was adequate (just barely!) back in the '60s. Increases in modern line voltage has pushed the B+ over 525V, especially if you are using a SS rectifier. Pull the output tubes when you get the caps replaced and see just how high the B+ really is.

[jjasilli]

I suggested abandoning the cap can idea.

OK in theory.  But: there's already a hole in the chassis for the can.  Depending on the amp, there may be limited space in the chassis to house individual filter caps.  When restoring a vintage amp, this may force creative solutions and planning for values & size dimensions, to mix new cap cans with stand-alone caps to get required uF & voltage ratings; fill holes in the chassis, and make sure everything will physically fit.

[sluckey]

OK in theory.  But: there's already a hole in the chassis for the can.

So leave the can in place. Or spend $50 for a direct replacement and you will still have to add series caps for at least the first and second nodes, preferably all four nodes.

My recommendation was not generalized but rather specific to the 200S or any other Sunn bass amp of that era. I know that there is plenty of room under that chassis. That amp could have been built on a chassis half the size. But then it would not have the big, powerful look of the other Sunns. And BIG was a big deal back then. All the heads were big and the same size.

Sunn guitar amps with reverb and tremolo were much more crowded under the chassis. On my Sceptre I opted to replace the can and the two 20µF/600v mainly for the space requirement.

[jjasilli]

I know that there is plenty of room under that chassis. OK, then I agree completely with sluckey.

[ernie_jr]

I have made this repair many times. In the hole i put a 32/32 at 500v cap can for stages 3 and 4. for stages 1 and 2, I use 100mFd at 350v mounted on a small board using Dougs turrets. Resistors go on the bottom of board, caps on top. Board size is about 2 in x 2 in square. Lots of room under the chassis and you have no open hole left.
Good luck,
Ernie

[SoundmasterG]

I have made this repair many times. In the hole i put a 32/32 at 500v cap can for stages 3 and 4. for stages 1 and 2, I use 100mFd at 350v mounted on a small board using Dougs turrets. Resistors go on the bottom of board, caps on top. Board size is about 2 in x 2 in square. Lots of room under the chassis and you have no open hole left.
Good luck,
Ernie

Ernie's approach is a good one. Incidentally, you can get custom cap cans from Webervst where they have seperate grounds, so you could go with that approach and wire up cap cans in series, but why bother. Discrete caps are smaller and cheaper and you can make stuff fit easily with today's caps.

Greg

P.S. You'll probably see somewhere around 560v B+ with the solid state rectifier...

[Ed_Chambley]

Job complete.  Really nice sounding amp.  Ended up just using 2 series 100uf/475v and a dual cap can as the voltage drop was sufficient.  Plates ended up being 563vdc loaded.  The chinese tubes did not survive.  I am sure they had a hard life anyway.  Did test a different tone stack and it is a very powerful and clean amp.  I really like it for guitar as well as bass.  It has more volume than I thought it would using bass.  Doesn't like the low b on a 5 string bass, but with a 4 string P bass it sounds great.

Yards of room in the chassis.  Left the old cap can and covered the rectifier socket.  Cleaned up and back in the hands of the happy owner.

Thanks for the input.