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In Reply to: RE: Slight change in power supply cap value - problem ?? posted by Caucasian Blackplate on June 16, 2015 at 05:51:09
Thank you very much for your reply. I tried to find a schematic for these, and had absolutely no luck. Also tried to ohm them out, but couldn't figure out an effective method. Given the way they always seemed to be used in circuit applications, I assumed that they were configured in a stacked / series configuration. Looks like that may have been an error.....
If indeed these are parallel rather than series, then it complicates things quite a bit..... Do you know these, and can you please let me know. These and the iron were pretty much what I got from someone's abandoned project, and I was hoping I could use them.
Regards -- Roger
Follow Ups:
All those caps have a shared ground, so you can't wire the internal halves in series.
You have two 2x100uF/500V caps in that photo. Parallel each cap to make two 200uF/500V caps, then wire each of those in series. No doubt this is what the project's originator intended.
The other cap was probably intended to serve as the 200uF/350V filter cap for the driver.
Thanks very much. Could I also use the 2 x 220 in the bottom portion of the high voltage stage, since there is a common ground there (both sides of the choke) and then stack a parallel 2 x 100 capacitor on either side? I realize there would be a slight capacitance difference, but would that matter??
I am aware of the filament supply. There are 3 variants of the design, and one of the other schematics has all the associated information (missing some watt information on some of the resistors, but I think I can calculate those out close enough). Thanks for asking though. I am trying to pay attention to every little detail since I have not done this before and want to do it right. I know there are not a lot of components associated with the build, but I figure they are all important or things will not come together well or properly.
Regards -- Roger
When you calculate resistor wattage with Ohm's Law, triple what you get and use a resistor of at least that power.
I wouldn't recommend putting two different electrolytic caps in series. We aren't talking about a ton of cash for caps here, just spend $50 and do it the right way.
Hello,
I put together a drawing of what I tried to describe above. I was thinking that one pair of caps has the 440 in between, and the other a resistor divider leg (perhaps not best description), so not strictly in series. Is this what you were concerned about? If so, suggestions on alternatives would be appreciated.
Regards -- Roger
Do this instead.
Hello,
If the dual capacitors are structured as you say, with a common -, then this is impossible. In your diagram the lower 1/2 220 has the - tied to ground, and the upper portion would require the - tied to 440.
Regards --Roger
I might suggest that you are way, way over your head on this project.
The upper capacitor is one can capacitor with the two halves paralleled.
The bottom capacitor is one can capacitor with the two halves paralleled.
You ground the ground of the bottom can capacitor.
You connect the positive side of the bottom capacitor to the negative side of the upper capacitor.
Hello,
That is what is depicted in my schematic, if you look closely. Each upper capacitor (2x100uf) is independent and the - is connected to the + of the capacitor below it. Fortunately the - terminals of both lower capacitors are connected to ground, allowing the use of a common ground dual capacitor.
In your schematic, the two capacitor segments on the right side share a ground ( - terminal) - they are the 2 halves of the 2 x 220uf capacitor. It is not possible to connect the + of one side of that capacitor to the - of the other half, because there is only one - for both capacitor sides and you already have it connected to ground. Maybe the terminology of 1/2 of 2x220 was not clear.....
Regards -- Roger
Ah, I thought the two capacitor symbols wrapped in a shroud represented two capacitors inside one can.
In any case, you have two 2x100uF caps, use each one like a 200uF/500V cap, and stack them for the first stage. For the second stage, purchase another pair of identical capacitors.
Hi,
Thanks for the resistor recommendation - will do.
Sorry if this is a dumb question, and perhaps I am misunderstanding, but what are you suggesting by way of a 200uf 500v cap that is not electrolytic??
Regards -- Roger
"Sorry if this is a dumb question, and perhaps I am misunderstanding, but what are you suggesting by way of a 200uf 500v cap that is not electrolytic??"
I never really said anything about a non-lytic cap. Just buy several 220uF/500V caps that are the same where you need to put them in series.
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