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Any Reason why you should build the doubler/rectifier on top of the Caps?

ElectronTubesRule

Active Member
Sep 6, 2011
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I see some guys put their diodes, resistors and such directly on top of the caps. Some people build it in the form of a board with traces going from the common diode and common resistor banks over to the caps which are also grouped together.

SO is their a best practice or does it not matter at all? I am just wondering which way if more durable. I was thinking that if built on top ofthe caps air can flow totally around the parts. If I build it on a board then the heat is concentrated and air flow is not as good.

I guessing I am over thinking it but it does hurt to ask?!?!
 

Yes I have been reviewing all online photo's of home brew amps using Russian Mil Surp. tubes. I say 2-3 that had their diodes and resistors directly on top of their cap banks. In all cases these are non-English speakers and a lot of dead links. I tried contacting these guys early on to ask why they did it that way but this was like 3-4 months ago. I have been doing research and digging for a while. I am excellent at research. Out of the 10 or so people I have tried to contact outside of the USA maybe 3 have gotten back to me. Non of the ones that responded though did the diode and resistors on cap layout.


I was just wondering why they did it that way. I was planing on doing mine on a perf board any way. I have noticed though that out of all the boards I have looked at online no one seems to obey the general rule of thumb I was taught on H.S.! I was taught that you should keeping your parts 1/4 above the board so air can circulate around the parts. Even on my mass produced linear that have rectifier boards the parts are all the way down on the surface of the circuit board no air space at all.

As to not seeing something before prior to looking online at homebrew amps out of Europe I had never seen a toroidal primary transformer used in an RF amp. Sure I have seen plenty of them in home audio amps but never in 1000 watt plus RF amps. So just because you have not seen something before really is not very meaningful. Just like I have never actually worked on or even looked inside a desk top amp using nothing but doubler,trippler etc.....and main power. So nothing surprises me when it comes to electronics where their is so many ways to skin a cat.

So it is safe to assume that few people do it that way. Oh I should say that you do see it a lot in projects where people are playing around with super high voltages like 30K volts at .5 amps etc.........Their is one online that has caps from 20 or 30 microwaves and is using microwave type diodes I think as well. They have the diodes and resistors built directly in the wiring of the caps in a cascade set up if I recall now.
 
Having the circuit board holding the rectifier circuit mounted over a bank of filter caps isn't unusual. Most of the amplifiers I've ever owned were built that way. The only thing, or components I've seen mounted directly on top of a filter capacitor, that is, using the contacts of those capacitors for mounting purposes, have been 'bleed off' resistors.
I have to agree with you, just because I haven't seen it certainly doesn't mean it hasn't been, or isn't done a particular way! I honestly can't think of any reason for building 'directly' on top of the capacitors though.
As for mounting parts "1/4" inch (?) above a circuit board for cooling purposes, while it may provide a very small additional bit of cooling, it certainly won't be much. Looks nice though.
- 'Doc
 
Well Unit_399 I would say you are foolish because you think you know it all which is the quickest way to look like you know nothing when you think you know it all! I learned that lesson when I was 8 years old. So I would learn to keep ones mind more open to being shocked by what you think you know not always being accurate!I on the other hand assume I know nothing and that todays facts are tomorrows fiction

Cascade Voltage Multiplier 30kV false hoods.


Here if you decide you are able to learn new tricks unlike some old dogs check it out! Due take note of the diodes directly on top of the caps. Also how do you figure that Microwave do not use electrolytic caps??? Their are all kinds of electrolytics inside a microwave oven.
 
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E...T...R...

I think both examples are good. The type of capacitor in question have mounting brackets to hold the capacitor in place and screw terminal for connection, either 4-40 or 6-32 threads on the opposite end. Good place to securely mount the parts associated with the capacitor.

You get a secure mount and short leads. Both desirable attributes.

My 2 cents

Mike

P.S. Looking closer I see one example ty-raps the capacitor to the side wall. Still a secure mounting for the capacitor, just not what I had first thought.

old 813 homebrew Amp

If you look at this photo you can see the diodes on top of the caps. You will also see two MOT as the power source. This was not the images I saw before I just accidentally found this just now.

Another accidental find where we have components stacked on top of caps.4-1000A Homebrew Amplifier
 
About those 'diodes' on the caps of the tubes in that 813 amplifier. First, they are not diodes at all, but a resistor with a small coil wound on them. They are commonly used for suppression of various sorts of things with tube amplifiers. A diode connected in their place would sort of defeat the purpose of the tube, wouldn't it?
As for capacitors and diodes in a microwave oven, please show me where I ever said there wasn't such a thing.

So, if you wanna teach some of us 'old dogs' new tricks, I think you'd first better learn to identify parts. Those voltage multiplier circuits have been around for a very long time. :)
- 'Doc
 
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About those 'diodes' on the caps of the tubes in that 813 amplifier. First, they are not diodes at all, but a resistor with a small coil wound on them. They are commonly used for suppression of various sorts of things with tube amplifiers. A diode connected in their place would sort of defeat the purpose of the tube, wouldn't it?
As for capacitors and diodes in a microwave oven, please show me where I ever said there wasn't such a thing.

So, if you wanna teach some of us 'old dogs' new tricks, I think you'd first better learn to identify parts. Those voltage multiplier circuits have been around for a very long time. :)
- 'Doc

Do voltage multipliers supply any usable current or are they just a flash in the pan like say a 3 mfd cap?
 
Usable current? I guess that just depends on how much current you need for some particular purpose. If you need enough to supply gobs of continuous current, then probably not. It takes time to recharge those caps so they can discharge and provide that multiplied/increased voltage. But if you don't need gobs of current, then it -may- furnish enough current to fill the requirement.
Take a look at the Tazers. Or those old cattle prods. That's how they work. Or at automotive ignition systems, that's why they work too. It isn't the current that's required, but the high voltages.
- 'Doc
 
Usable current? I guess that just depends on how much current you need for some particular purpose. If you need enough to supply gobs of continuous current, then probably not. It takes time to recharge those caps so they can discharge and provide that multiplied/increased voltage. But if you don't need gobs of current, then it -may- furnish enough current to fill the requirement.
Take a look at the Tazers. Or those old cattle prods. That's how they work. Or at automotive ignition systems, that's why they work too. It isn't the current that's required, but the high voltages.
- 'Doc

I've been on the business end of both of those devices and I'll say it was not a pleasant experience but on the other hand I've been on the been on the business end of a device supplying 1 amp at a lower voltage and that one turned a couple of my toe nails black where the current attempted to exit my body so I know there is no substitute for heavy current supply.

I suppose that's what you get for trying to make current with caps instead of a transformer and some decent rectifiers.
 
Have a friend who carry's one of those tazers. He asked if I'd like to see what it does. I told him that I'd just as soon have him shoot me than hit me with one'a them things. I figure I can take that before getting shocked again. Also told him he'd better get me good, or I'd beat him to death with the @#$ thing.
Any of that meant seriously? Not really, except for the beating thing...
- 'Doc
 
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Have a friend who carry's one of those tazers. He asked if I'd like to see what it does. I told him that I'd just as soon have him shoot me than hit me with one'a them things. I figure I can take that before getting shocked again. Also told him he'd better get me good, or I'd beat him to death with the @#$ thing.
Any of that meant seriously? Not really, except for the beating thing...
- 'Doc

I have a buddy on the local PD and he asked the same thing when showing me his new Tazer. My reply to him was about the same "When I do get up, you better hope you have at least a 3 county lead on me" :laugh:
 

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