Voltage Doublers.........

[Jack_Hester]

I'm working some long hours on night shift, at the plant.  So during my breaks, and with ISOtone's doodling in mind, I've been looking over many methods of building voltages doublers.  I don't have a practical need for one, at the present.  But, it fills the long hours of boredom.  I've sketched out what appears to be a less than simple version that I found:



And, my tube rendition of the same:



And, my low resolution AutoCAD saved graphics version of both:



The tube version is not very practical, but was fun to draw.  I've read the other posts on the same subject, but post my own.  Will probably not build either, anytime soon.  But, would like to compare the outputs of each, unloaded and loaded.  I have the .sch and .dwg files that I can post, but don't know how to attach them to this thread, like I've seen done on other threads.  Someone please coach me on how to do so.  I'll try it, when I get off tomorrow morning, and am not too brain dead.  Have a good one.

Jack

[SoundmasterG]

Kevin O' Connor has a four diode, two cap full wave voltage doubler in his TUT books that I have used in a couple amps, and it works well. A lot of vintage organ and PA amps used voltage doublers, but they were often half wave. The cap values used are higher value and lower voltage than you might think, but in the end a pair of 150uf 300v caps end up being basically a 75uf cap for that filtering stage. I like doublers myself....they give you some of the sag of a tube rectifier, but the diodes won't be wearing out. They tend to be a bit noisier than amps without them, but you can get around that.

Greg

[Jack_Hester]

Kevin O' Connor has a four diode, two cap full wave voltage doubler in his TUT books that I have used in a couple amps, and it works well. A lot of vintage organ and PA amps used voltage doublers, but they were often half wave. The cap values used are higher value and lower voltage than you might think, but in the end a pair of 150uf 300v caps end up being basically a 75uf cap for that filtering stage. I like doublers myself....they give you some of the sag of a tube rectifier, but the diodes won't be wearing out. They tend to be a bit noisier than amps without them, but you can get around that.

Greg

Good info, Greg.  Do you have a sketch of the layout?  Thanks for the reply.

Jack

[DummyLoad]

just doodling...

VFWD...

i'm not sure it'll work w/ center taps on the filament windings, but can't can't think of a reason why it wouldn't... otherwise, move CT connections to top of 5V windings.   

--ISO

[Jack_Hester]

How do I attach/link my .sch and .gif files to a post, such as you and others do?  Thanks.

Jack

[DummyLoad]

reply

button in left lower corner of reply panel    "+ Additional Options..."  click on it

select browse - chose the file.

click "more attachments" to attach an additional file.

[Jack_Hester]

Got it!  Will give it a try when I get home.  Thanks.

Jack

[PRR]

Man, that's a brain-buster.

What is the voltage rating on the middle caps? Heck, what is their polarity?? Oddly, they seem to come to zero volts -after- start-up, but need a large rating for the first few cycles.

Output voltage is identical to several 2-D 2-C doublers. It _is_ 120Hz ripple instead of 60Hz like simple doublers.

I think what you got is more parts, possibly smaller values/ratings, but usually soup is cheaper in big cans and two 50uFd cost more than one 100uFd.

As vacuum rectification, it really sucks: four isolated cathodes, common cathodes are cheaper.

With "275-0-275" winding the output is 1,500 volts, which is higher than we usually want.

The "275-0-275" winding is probably proportioned for an audio amp with 4K-8K load. A FWB would give twice the voltage (since we "mis-use" the CT). The doubler gives 4 times normal voltage. No free lunch OR power, so current is like 1/4. Now your impedance must be 4^2 or 16 times higher... 64K to 128K.

I'm not finding 1,500V tubes nor 100K OTs in the usual places.

A straight 120VAC winding would double-up to 330V DC, which is useful if you have scrap isolation transformers. Some HVAC guys have scrap 24V iron, but that's like 66V, not real exciting.

Doublers generally "do not make sense" with vacuum rectifiers because you start with a low AC voltage and then have TWO diode losses. It was done in a few transformerless rigs. 110VAC doubled with two bottle losses gives 200V, far short of ideal 300+VDC, but acceptable as an in-between from 105VDC 1-Watt rigs and proper PT-powered 300V 5-Watt rigs.

[Jack_Hester]

Man, that's a brain-buster.

What is the voltage rating on the middle caps? Heck, what is their polarity?? Oddly, they seem to come to zero volts -after- start-up, but need a large rating for the first few cycles.

Output voltage is identical to several 2-D 2-C doublers. It _is_ 120Hz ripple instead of 60Hz like simple doublers.

I think what you got is more parts, possibly smaller values/ratings, but usually soup is cheaper in big cans and two 50uFd cost more than one 100uFd.

As vacuum rectification, it really sucks: four isolated cathodes, common cathodes are cheaper.

With "275-0-275" winding the output is 1,500 volts, which is higher than we usually want.

The "275-0-275" winding is probably proportioned for an audio amp with 4K-8K load. A FWB would give twice the voltage (since we "mis-use" the CT). The doubler gives 4 times normal voltage. No free lunch OR power, so current is like 1/4. Now your impedance must be 4^2 or 16 times higher... 64K to 128K.

I'm not finding 1,500V tubes nor 100K OTs in the usual places.

A straight 120VAC winding would double-up to 330V DC, which is useful if you have scrap isolation transformers. Some HVAC guys have scrap 24V iron, but that's like 66V, not real exciting.

Doublers generally "do not make sense" with vacuum rectifiers because you start with a low AC voltage and then have TWO diode losses. It was done in a few transformerless rigs. 110VAC doubled with two bottle losses gives 200V, far short of ideal 300+VDC, but acceptable as an in-between from 105VDC 1-Watt rigs and proper PT-powered 300V 5-Watt rigs.

I found the original article here:

http://www.kwarc.org/bulletin/99-04/tech_corner.htm

and the author stated that his application was for very high voltages, particularly Amateur Radio.  As to the 275v, that was a mistake on my part.  I have a power transformer saved in AutoCAD for generic use, and it has the text for the voltage as shown in my drawing.  I meant to deleted the text, but overlooked it.  As to the tube version, I didn't think that it was practical when I drew it.  But, hoped that someone would confirm that I drew it correctly.  I picked the 6BY5's, because I have some of them.  I may still construct one, just for grins, to compare the outputs with the diode version, fed with an autotransformer.  Not sure how I would load them, as I don't have an adjustable carbon pile, like we use at work.  Being as we're dealing in mAmps, I think I have an old rheostat, of fairly high wattage, that I can press into service. 

Anyway, it is just a means to fill the gaps in time, until I'm called out on support of the 2 Unit outages in progress.  I make pencil sketches, and CAD them when I first get home.  No pencil sketches tonight, as things have been 'interesting' to say the least, on this shift.  Thank goodness I'm back on days next week.  Please comment as to whether my tube sketch is correct, or needs adjusting.  Thanks for looking.

Jack

P.S. - It ain't amp building, but it makes for good study of the components.

[DummyLoad]

The tube version is not very practical, but was fun to draw.   Will probably not build either, anytime soon... 

the general consensus is that circuit is very dangerous - it's full floating, in that you cannot ground the output cap to chassis that has a bonded earth ground. if you do it goes boom!

it is intended to be powered with an isolation transformer.

does not seem practical for what we do (geetar amps).

--ISO

[Jack_Hester]

the general consensus is that circuit is very dangerous - it's full floating, in that you cannot ground the output cap to chassis that has a bonded earth ground. if you do it goes boom!

it is intended to be powered with an isolation transformer.

does not seem practical for what we do (geetar amps).

--ISO

Still, a good study.

Jack

[DummyLoad]

the general consensus is that circuit is very dangerous - it's full floating, in that you cannot ground the output cap to chassis that has a bonded earth ground. if you do it goes boom!

it is intended to be powered with an isolation transformer.

does not seem practical for what we do (geetar amps).

--ISO

Still, a good study.

Jack

agreed, however if you do build it... build 6V/12V system - that way if it do go boom it's just a bit of confetti - use fuses to skirt around the confetti part(y).

[Jack_Hester]

agreed, however if you do build it... build 6V/12V system - that way if it do go boom it's just a bit of confetti - use fuses to skirt around the confetti part(y).

Right you are.  Actually, my thoughts are to feed it with a lamp limiter, first.  Like I would do with a new amp build.  Do some voltage checks, and then swap over to an autotransformer to begin some voltage measurements from very low voltages.  All this on a SS version.  Then, if it checks out well, try it on a tube version.  Again, no practical use for the tube version other than proof of working.  I have the old tubes on hand, plus I have a number of old bakelite sockets salvaged from the scrap heap several years ago.  The guys at work bring this stuff and lay it on my bench.  Good fellows.  I got a few 1N5048 diodes that have been laying around for years.  Heavy duty stuff, just right for something like this.  I'll leave the leads long, so that they can be used elsewhere if needed.

Thoughts?  I appreciate the feedback, even though it's not entirely amp building. 

Jack

[SoundmasterG]

Kevin O' Connor has a four diode, two cap full wave voltage doubler in his TUT books that I have used in a couple amps, and it works well. A lot of vintage organ and PA amps used voltage doublers, but they were often half wave. The cap values used are higher value and lower voltage than you might think, but in the end a pair of 150uf 300v caps end up being basically a 75uf cap for that filtering stage. I like doublers myself....they give you some of the sag of a tube rectifier, but the diodes won't be wearing out. They tend to be a bit noisier than amps without them, but you can get around that.

Greg

Good info, Greg.  Do you have a sketch of the layout?  Thanks for the reply.

Jack

Hi Jack,

I don't have a sketch of the layout...it is in Kevin's books and is copywrited so I won't post it. It is just a 4 diode 2 cap doubler that gives 120Hz ripple at one node and 60Hz at the other node. You could probably find it elsewhere or perhaps email Kevin and see if he is amendable to sharing it with you.

Greg

[Jack_Hester]

Greg -

I'll look for his contact info and see if he will oblige me with a picture/sketch.  I believe that I've now seen the layout that you describe, with the 4 diodes and 2 caps.  If I see it again, I'll document it from that source.  Thanks for mentioning it.  I'll try to keep record of them all.  As I alluded to before, it ain't amp building, but it still pertains.  Have a good one.

Jack

[SoundmasterG]

Greg -

I'll look for his contact info and see if he will oblige me with a picture/sketch.  I believe that I've now seen the layout that you describe, with the 4 diodes and 2 caps.  If I see it again, I'll document it from that source.  Thanks for mentioning it.  I'll try to keep record of them all.  As I alluded to before, it ain't amp building, but it still pertains.  Have a good one.

Jack

You can contact Kevin O' Connor at www.londonpower.com.

Cheers!

Greg

[Jack_Hester]

You can contact Kevin O' Connor at www.londonpower.com.

Cheers!

Greg

Thanks, Greg.  Have a good one.

Jack

[sluckey]

Sears built some amps that use voltage doublers. These amps actually use two doublers connected in series to give quadruple voltage output. Might help pass the long nights...

http://www.el34world.com/charts/Schematics/files/silvertone/silvertone1484.pdf
http://www.el34world.com/charts/Schematics/files/silvertone/silvertone1485.pdf

[Jack_Hester]

Sears built some amps that use voltage doublers. These amps actually use two doublers connected in series to give quadruple voltage output. Might help pass the long nights...

http://www.el34world.com/charts/Schematics/files/silvertone/silvertone1484.pdf
http://www.el34world.com/charts/Schematics/files/silvertone/silvertone1485.pdf

This will be quite a challenge for a tired brain.  But thanks for the links.  I've got a number of lengthy breaks tonight, as the people I'm supporting are taking off early, but I'm here 'til daybreak.  Should be able to work them out by then.  Thanks, again.  Have a good one.

Jack

[Jack_Hester]

I'll regress a bit in this thread and post a sketch of a doubler that was in a reprint of the RCA book, RC-30.  Couldn't find my original, from '71-'72.  I'm assuming that the same drawing would be in it. 



I took the license of adding a power transformer, and different tubes.  The book had the circuit connected directly to AC line voltage, no transformer.  It also cautioned about grounding.  Also, the book showed tubes beginning with a 25, but I don't have it close by to give the exact tube.  I drew in 6AU4's, as I have some of those.  I made my previous sketches with multiple diodes from the SS drawings. 

Jack

[GEO62]

I see that on the schematic. Does anyone have a model of a replacement Power transformer or the specs for the original?