GMoretti@massey.ac.nz (Giovanni Moretti) (07/26/90)
Peridically I get the feeling that radio ... is getting far too hard to do - you need 99%+ pure Ge/Si ... and huge factories and $00000000. One the other hand: You can make resistors out of pencil leads, capacitors and inductors are easy, headphones are possible (not easy) and you can use Galena (lead sulphide I think for a diode), but what about things with GAIN. I've had this dream of making a triode in a peanut butter jar (a small strong one :=) ... Has anyone out there ever tried to make something like this or any homemade semiconductors .... And how about batteries with household chemicals (ie not sulphuric) I can't be the only one who has these thoughts ... Cheers Giovanni -- ------------------------------------------------------------------------------- | GIOVANNI MORETTI, Consultant | EMail: G.Moretti@massey.ac.nz | |Computer Centre, Massey University | Ph 64 63 69099 x8398, FAX 64 63 505607 | | Palmerston North, New Zealand | QUITTERS NEVER WIN, WINNERS NEVER QUIT | -------------------------------------------------------------------------------
cccph@eel.cs.ucla.edu (Charles Hobbs) (07/26/90)
In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: + + (stuff deleted) + > You can make resistors out of pencil leads, capacitors and >inductors are easy, headphones are possible (not easy) and you can >use Galena (lead sulphide I think for a diode), but what about things >with GAIN. Homemade semiconductors, other than diodes, may be a problem; see below. >I've had this dream of making a triode in a peanut butter jar (a >small strong one :=) ... You could do this successfully if you had some way of getting a good vacuum. (Commercial valves have chemical compounds known as "getters" which aid in removing oxygen from the valve) >Has anyone out there ever tried to make something like this or any >homemade semiconductors .... Transistors, etc. would most likely be too difficult to make at home because of the necessity for "clean rooms" (rooms with no appreciable level of dust floating around. Dust will short-out a transistor, integrated circuit, etc.) >And how about batteries with household chemicals (ie not sulphuric) Try lemon juice.... -------------------------------------------------------------- | Charles P. Hobbs | Rail transit has arrived in LA! | cccph@eel.cs.ucla.edu | Hear the action >right now< on | N6YMK @ K6VE | >>>> 471.3375 mHz <<<<!
brian@ucsd.Edu (Brian Kantor) (07/26/90)
Well, actually, I've never made any vacuum tubes, but I have made some semiconductor material - there used to be these nifty science experiment kits that Bell Labs put out, and in one of them you made a photocell from a wafer of silicon, rat poison, and some other wonderous stuff. I like to think it helped me pass the semiconductor physics course I took much later in college. My Grandfather, on the other hand, used to make triode vacuum tubes all the time. Of course, he was working for Lee De Forest at the time. (BTW, gramps was a ham too - his call was 2RH, and somewhere around here I have one of his licenses, signed by Herbert Hoover. He didn't keep any of the tubes, though.) He got bored with vacuum tubes and went to work as a test pilot for Igor Sikorsky. At the age of 85, legally blind, he used to race his motorcycle around the trailer camp where he lived down in Florida, terrorizing women and children alike. And you guys think I terrorize the net? Just wait until I get to be as wild as grandpa was.... - Brian
ardai@teda.UUCP (Mike Ardai) (07/26/90)
In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: >And how about batteries with household chemicals (ie not sulphuric) How about using a lemon with a nail and a penny stuck in it? Or a voltaic pile made out of stacks of pennies and silver dimes with salt-soaked blotter between them? /mike -- \|/ Michael L. Ardai Teradyne EDA East --- ------------------------------------------------------------------------- /|\ ...!sun!teda!ardai (preferred) or ardai@bu-pub.bu.edu
grege@gold.GVG.TEK.COM (Greg Ebert) (07/26/90)
In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: > >And how about batteries with household chemicals (ie not sulphuric) > I managed to get a voltage reading from a lemon - I used a penny (copper) for one electrode, and the meter probe for the other. It was under a volt. I prefer to power-up lemons and potatoes with 220 volts.....
sreekanth@rgb.dec.com (Jon Sreekanth) (07/26/90)
In article <872@massey.ac.nz>, GMoretti@massey.ac.nz (Giovanni Moretti) writes... >Peridically I get the feeling that radio ... is getting far too hard >to do - you need 99%+ pure Ge/Si ... and huge factories and $00000000. > >Has anyone out there ever tried to make something like this or any >homemade semiconductors .... > >| GIOVANNI MORETTI, Consultant | EMail: G.Moretti@massey.ac.nz | >|Computer Centre, Massey University | Ph 64 63 69099 x8398, FAX 64 63 505607 | >| Palmerston North, New Zealand | QUITTERS NEVER WIN, WINNERS NEVER QUIT | >------------------------------------------------------------------------------- Yes, anything at all to do with semiconductors is expensive, because you need ultra clean rooms, fine geometries, and dangerous chemicals. (And I mean _real_ semiconductors, not cats whiskers :-) But ... there`s a way. MOSIS (1-213-822-1511) is the best bet for the small experimenter. $500 gets you 4 packaged parts in cmos 2 micron technology, 132 pin pga max. They have a modem number; you give them yoiur design data base in electronic form, and at their next scheduled run (they have runs every 1-2 weeks. ), they run your design through with many others, and mail you the parts. Good for prototyping an idea / Jon Sreekanth US Mail : J Sreekanth, 79 Apsley Street, Apt #7, Hudson, MA 01749 Digital Equipment Corp., 77 Reed Road, HLO2-1/J12, Hudson, MA 01749 email : sreekanth@rgb.dec.com Voice : 508-562-3358 eves, 508-568-7195 work
perley@galaxy (Donald P Perley) (07/27/90)
In article <37291@shemp.CS.UCLA.EDU>, cccph@eel (Charles Hobbs) writes: >In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: >You could do this successfully if you had some way of getting a >good vacuum. (Commercial valves have chemical compounds known as >"getters" which aid in removing oxygen from the valve) One thing that would help is to light up the tube for a bit with the vacuum pump still running so any initial outgassing can get sucked out. I'm not sure what is in the getters.. maybe those could be homebrewed as well? -don perley perley@trub.crd.ge.com
elkind@nodename.dec.com (Steven A. Elkind) (07/27/90)
In article <872@massey.ac.nz>, GMoretti@massey.ac.nz (Giovanni Moretti) writes... >Peridically I get the feeling that radio ... is getting far too hard >to do - you need 99%+ pure Ge/Si ... and huge factories and $00000000. > What about alloy junction germanium transistors - they should be doable in non-cleanroom circumstances, shouldn't they? I'd imagine the materials wouldn't be too hard to obtain, and the geometries are large enough that real clean room conditions wouldn't be all that necessary. The yield might be somewhat low, and the device parameters scattered all over the place with home-lab conditions, but I'd think you could get some usable devices with a modest amount of effort.
tweed@apollo.HP.COM (David Tweed) (07/27/90)
From: GMoretti@massey.ac.nz (Giovanni Moretti) > You can make resistors out of pencil leads, capacitors and > inductors are easy, headphones are possible (not easy) and you can > use Galena (lead sulphide I think for a diode), but what about things > with GAIN. > > I can't be the only one who has these thoughts ... You aren't; you're following the footsteps of a long string of hobbyists. From: cccph@eel.cs.ucla.edu (Charles Hobbs) > Transistors, etc. would most likely be too difficult to make at home > because of the necessity for "clean rooms" (rooms with no appreciable > level of dust floating around. Dust will short-out a transistor, > integrated circuit, etc.) Nah, you're thinking of ICs, where the dust messes up the photomasking. Remember, the first point-contact transistors were made by hand in the lab. A long time ago, I read a story about a person who built his own vacuum tubes at home. The story was old then, and I don't remember where I read it (probably Popular Electronics, back when it was still in the smaller format), but I'll try to summarize. (Disclaimer: I've never done this myself!) Back when tubes were first being developed, most of the publicized effort was going into the Edison/DeForest type of "tube" that was based on the light *bulb* and required glassblowing skills. However, there was a grassroots effort (primarily by Canadian experimentors, I believe) that was based on using a metal *tube*. It is this second type that is much easier to fabricate at home. Take a piece of tubing (copper, I think) and find some hard-rubber stoppers that fit it tightly, one with a hole, the other without. The one with a hole is fitted with a glass tube that gets connected to your vacuum pump. The metal tube itself is your anode; you still need a filament and a grid. Poke some fairly heavy-guage (#18) solid copper wires through the stoppers (making their own holes): one in one stopper, and two in the other. The filament (cannibalized from a light bulb?) gets stretched down the center of the tube, strung between two of these wires (crimped, not soldered!), and the grid is the third wire, spiraling around that. Remember that the filament is going to get pretty hot, so provide a fairly-long thermal path before you get to the stopper, otherwise you won't be able to maintain any sort of vaccuum. (The author of the article said that he'd forgotten this, and when he powered up his first tube, "... the vaccuum immediately left with a piercing shriek.") OK, put everything together and seal all joints with sealing wax. ("What's sealing wax?" :-). I'll try to do an ASCII picture: rubber copper tube rubber stopper =========================================== stopper ########## \ /-\ /-\ /-\ ########## ########## /\ | | | | | | \---------------- grid connection fil.-------------/ | | | | | | | ########## ########## +======|=======|=======|==+ ########## --------------- | | | | | | | /------------- filament (cathode) to --------------- | | | | | | | / ########## vaccuum ######## \-/ \-/ \-/ \/ ########## pump ===========================================-------- plate (anode) The loops in the filament wires help keep them from getting too hot where they go through the stoppers. Don't worry about all that stuff having to do with "getters", etc. Most experimentors just left the vaccuum pump running while they were operating the tube. At this point, pump out the air, apply power to the filament (carefully!) and to the anode (see if you get a current flow). Then experiment to see what kind of control you get with the grid. I'm sure it'll take a lot of cut-and-try to get any significant amount of gain, so have fun! -- Dave Tweed
taber@ultnix.enet.dec.com (Patrick Taber) (07/27/90)
In article <10368@crdgw1.crd.ge.com>, perley@galaxy (Donald P Perley) writes: |> >You could do this successfully if you had some way of getting a |> >good vacuum. (Commercial valves have chemical compounds known as |> >"getters" which aid in removing oxygen from the valve) |> [...] |> I'm not sure what is in the getters.. maybe those could be homebrewed |> as well? Scientific American published articles on making your own HeNe LASER back in the late 60's/ early 70's that among other things detailed making your own getters to purge the LASER tube. (I remember it because my buddy and I tried to make a LASER as a high-school science project. We got a nice tour from the folks at MIT out of it. Sadly, our mirror mounts never worked out.) >>>==>PStJTT Patrick St. Joseph Teahan Taber My employer doesn't care what I think. I, in turn, don't care what you think. You probably don't care what my empolyer thinks. Thus is life a circle.
adams@swbatl.sbc.com (Tom Adams - 235-7459) (07/27/90)
In article <37291@shemp.CS.UCLA.EDU> cccph@eel.cs.ucla.edu (Charles Hobbs) writes: >In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: >+ >+ (stuff deleted) >>I've had this dream of making a triode in a peanut butter jar (a >>small strong one :=) ... >You could do this successfully if you had some way of getting a >good vacuum. (Commercial valves have chemical compounds known as "getters" which aid in removing oxygen from the valve) Before I run off about getters, I'd like to mention that light bulb filaments have low emmissivity, and probally aren't suitable, and that a test tube, or olive jar would probally be a lot easier to evacuate. Also, using direct filament emmision means you'll need DC filament supplies to avoid hum. I quote from Physics of Electron Tubes, L. Koller, McGraw-Hill, 1937 (2e) No matter how well a vacuum tube has been exhausted, there always remains a small residual pressure of gas. This may perhaps be of the order of 0.0001mm of Mercury in commercial tubes. Even at this low pressure, the number of molecules of air per cubic centimeter reaches the astounding figure of 10^12. ... The getters most commonly used at present are phosphorus, calcium, magnesium, barium, strontium, aluminum and various mixtures of alloys of these. Phosphorus is used in the red form. ... Barium and strontium are very active getters but have the disadvantage of oxidizing rapidly... For this reason the are often used in the form of alloys with aluminum, which are quite stable in air and from which the active metal can be vaporized by heating, after exhausting the tube. ... [Discussion of reduction of gas pressure during getter vaporization by collision between getter and gas molecles, and later, after getter has volatized onto surface of tube wall by formation of monatomic layer of gas molecules, mentioning 10^2 cm layer could reduce pressure 3x10-3 mm Hg in 100 cc bulb.] I believe getters were vaporized by strong RF field, which also contributed to the vacuum by accellerating gas ions into the tube walls. Glass and electrode metals substantially outgas and must be heated for a considerable time to reduce this effect. Getters were actually invented by John T Marshall (1908) to exhaust tungsten filament lamps, and many others patented improved getters in the next few decades. All in all, soft tubes like Brian's grandaddy used to make would be a whole lot easier. Reasonable detectors, lousy amplifiers. Still could awfully interesting. Others have done tubes at home, and I've thought about it a lot. Anyone seen documents on Sprengel vacuum pumps as used by Edison? Send mail, join the languishing Antique Radio mailing list. -- uunet!swbatl!adams or adams@swbatl.sbc.com Tom Adams: 314-235-7459: Southwestern Bell Telephone Advanced Technology Lab BOOKS WANTED: pre-1930 radio, electrical & scientific topics
nanook@rwing.UUCP (Robert Dinse) (07/28/90)
In article <10368@crdgw1.crd.ge.com>, perley@galaxy (Donald P Perley) writes: > I'm not sure what is in the getters.. maybe those could be homebrewed > as well? > My understanding is a "getter" is magnesium that is "fired" with microwaves after the tube is evacuated.
bill@flash.UUCP (bill) (07/28/90)
In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti): >[...] You can make resistors out of pencil leads, capacitors and >inductors are easy, headphones are possible (not easy) and you can >use Galena (lead sulphide I think for a diode), but what about things >with GAIN. >I've had this dream of making a triode in a peanut butter jar (a >small strong one :=) ... I recall one of the hobby electronics magazines (Popular Electronics? Radio-Electronics?) ran an article on "liquid semiconductors" sometime between May '68 and June '69 - maybe it was the April 1st issue. :-) Don't know how they formed the PN junctions. :-) (I recall looking at the article, and yes, they were building components in jars - but I didn't have the money then to buy the magazine. Anyone else remember it? Now I am curious.) >And how about batteries with household chemicals (ie not sulphuric) I only tried once, in a few idle moments some time ago, with some alumin{i}um foil, square of paper, a copper penny, and saltwater. Got something like .6V open circuit, 1 mA short circuit (for a second or so, then it started to drop to some lower level). I'm sure it could be greatly improved. :-) [I've added sci.chem to this because this is getting into their realm. Any ideas, anyone? ..Larry? :-) ]
steve@nuchat.UUCP (Steve Nuchia) (07/28/90)
Back in high school it occurred to me that it might be possible to build a liquid state "tube". Immerse the electrodes in an electrolyte solution and see what you can make it do... I didn't know enough electronics, physics, or chemistry (though I thought I did) to give it a fair test at the time. Anybody know whether it is possible to get gain out of such a device? Granted its lifetime is very short, but it compares well with the properties of homemade vacuum tubes (if it works, of course). -- Steve Nuchia South Coast Computing Services (713) 964-2462 "To learn which questions are unanswerable, and _not_to_answer_them; this skill is most needful in times of stress and darkness." Ursula LeGuin, _The_Left_Hand_of_Darkness_
roy@phri.nyu.edu (Roy Smith) (07/29/90)
Having seen the phrase "liquid phase electronics" in print, it
occurs to me that "solid state electronics" is perhaps a bit of a misnomer.
Vacuum tubes are solid state too; they certainly don't have any liquid in
them and (if they are any good) don't have any gas either. What's left, if
not solid?
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"mcdonald@aries.scs.uiuc.edu (Doug McDonald) (07/29/90)
In article <1990Jul28.185816.13964@phri.nyu.edu> roy@phri.nyu.edu (Roy Smith) writes: > > Having seen the phrase "liquid phase electronics" in print, it >occurs to me that "solid state electronics" is perhaps a bit of a misnomer. >Vacuum tubes are solid state too; they certainly don't have any liquid in >them and (if they are any good) don't have any gas either. What's left, if >not solid? >-- Well, tubes without vacuum are vacuum tubes, so .... But there are common electron tubes that DO contain gas (hydrogen, argon, neon, or mercury) or liquid (mercury). Doug McDonald
gin@stcvax.STORTEK.COM (George Noyes) (07/31/90)
In article <10368@crdgw1.crd.ge.com>, perley@galaxy (Donald P Perley) writes: > In article <37291@shemp.CS.UCLA.EDU>, cccph@eel (Charles Hobbs) writes: > >In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: > > >You could do this successfully if you had some way of getting a > >good vacuum. (Commercial valves have chemical compounds known as > >"getters" which aid in removing oxygen from the valve) > > I'm not sure what is in the getters.. maybe those could be homebrewed > as well? > "Getters" - typically barium, sometimes cesium or other metals that are highly reactive to oxygen (and sometimes nitrogen). Magnesium and "Lime (Calcium carbonate)" have been used in antique (pre 1930) tubes. fyi george noyes, W1XE
kimf@arrester.caltech.edu (Kim Dorian Flowers) (07/31/90)
taber@ultnix.enet.dec.com (Patrick Taber) writes: >In article <10368@crdgw1.crd.ge.com>, perley@galaxy (Donald P Perley) writes: >Scientific American published articles on making your own HeNe LASER >back in the late 60's/ early 70's that among other things detailed >making your own getters to purge the LASER tube. (I remember it >because my buddy and I tried to make a LASER as a high-school >science project. We got a nice tour from the folks at MIT out of it. >Sadly, our mirror mounts never worked out.) Omigod! I tried to make a laser for my freshman year in college and I couldn't get it to work because of the mirror mounts also...I'm SO glad I wasn't the only person to run into this problem. Now I can deal with my inferiority complex :) ...sob... Kim Flowers
ghg@ecn.purdue.edu (George Goble) (08/01/90)
Built a couple of triodes for my 8-th grade science project back in the 60's. I sort of cheated and used the filament from a busted 5U4GB (rectifier) tube, but used a piece of window screen for the grid. The grid & plate were attached to a movable assembly (alligator clips), so they could be moved around and the characteristics observed. One would have to take the tube apart to do this.. Had a 2 stage vac pump on loan from Earlham College then to pump it down. Vessel was a "Gerber" baby food jar. The lid was the plate connection & vac connection, grid + fil came thru holes drilled in the bottom, sealed with epoxy (had just been invented back then). It seemed to work. Was able to get voltage gains of 10X or so I recall in the linear region. Put a cricket in one once, and hit it with a neon sign xfmr (9KV, 30ma) during the pumpdown.. all kinds of St Elmo's fire off the cricket's legs and sharp edges. Cricket was knocked out, but later revived after the 3-4 min session. --ghg
dnl@goanna.cs.rmit.oz.au (David "IGOR" Latter) (08/01/90)
>Scientific American published articles on making your own HeNe LASER >back in the late 60's/ early 70's that among other things detailed >making your own getters to purge the LASER tube. (I remember it >because my buddy and I tried to make a LASER as a high-school Does anyone know the issue that this appeared in? I am currently setting up a pumping system to resore vintage radio tubes and would find the information interesting. Eventually I intend to re-create replacement parts for pre 1930 radio gear for the Historical Radio Society of Australia members. David.
mhughes@loft386.uucp (Mike Hughes) (08/01/90)
>And how about batteries with household chemicals (ie not sulphuric)
See If you can find a copy of "Things a Boy Can Do With Electricity" by
Alfred Morgan (1951). This has plans for batteries, rectifiers and
photoelectric cells, all in jars with very basic chemistry. Nothing with
gain, however.
Lots of other delightful things too!
--
Mike Hughes
Lofty Pursuits (Public Access for Rapid City SD USA)
bigtex!loft386!mhughesdel@thrush.mlb.semi.harris.com (Don Lewis) (08/01/90)
In article <1990Aug1.023331.20141@loft386.uucp> mhughes@loft386.uucp (Mike Hughes) writes: >>And how about batteries with household chemicals (ie not sulphuric) > >See If you can find a copy of "Things a Boy Can Do With Electricity" by >Alfred Morgan (1951). This has plans for batteries, rectifiers and >photoelectric cells, all in jars with very basic chemistry. Nothing with >gain, however. > >Lots of other delightful things too! I seem to recall reading "The Boy Electrician" by the same author many years ago. It had lots of plans for spark coils and tesla coils, told how to use X-ray tubes :-O, etc. He also had some more recent books on how to build things intercoms and audio amps (5 watts, wow!). -- Don "Truck" Lewis Harris Semiconductor Internet: del@mlb.semi.harris.com PO Box 883 MS 62A-028 Phone: (407) 729-5205 Melbourne, FL 32901
francis@cs.ua.oz.au (Francis Vaughan) (08/01/90)
In article <1990Aug1.081830.15979@mlb.semi.harris.com>, del@thrush.mlb.semi.harris.com (Don Lewis) writes: |> |> I seem to recall reading "The Boy Electrician" by the same author many |> years ago. It had lots of plans for spark coils and tesla coils, told |> how to use X-ray tubes :-O, etc. He also had some more recent books |> on how to build things intercoms and audio amps (5 watts, wow!). This was one of the all time great books in my opinion. What a book! I buit a few things from this book, (the Tesla coil being my favorite). The recent books were not nearly as good (not written by J W Simms, but someone cashing in on the success of the older books). Some of the projects were frightening in the level of danger. One chapter describes how to recharge secondary cells from the DC mains. (This WAS written a while ago.) How do you tell if it is DC? Stick the wires in a grass of water, is one wire bubbles twice as much as the other you know it is DC, and you also know the polarity! The stuff and X-Rays also totally ignorant of the dangers. He suggests that an X-Ray tube can be purchasd for 5 shillings! It aslo described how to build your own primary and secondary cells (carbon zinc and lead acid). These were not toy projects, but intended as replacments for commercial products. A complete description of a telephone to build, motors AC and DC, morse code stuff. Absolutely fascinating stuff. Francis Vaughan
roth@smoot.enet.dec.com (Lee Roth) (08/03/90)
In article <1990Aug1.081830.15979@mlb.semi.harris.com>, del@thrush.mlb.semi.harris.com (Don Lewis) writes... > >I seem to recall reading "The Boy Electrician" by the same author many >years ago. It had lots of plans for spark coils and tesla coils, told >how to use X-ray tubes :-O, etc. He also had some more recent books >on how to build things intercoms and audio amps (5 watts, wow!). >-- "The Boy Electrician" had a copyright circa 1930. Great book, but the local library has purged it in favor of newer stuff. Was the only book readily available when I was a kid that had details for building induction coils. I made a fine one with magnet wire from Allied Radio and model-T coil points I ordered from JC Whitney. It would shock the p__s out of you! The book was sufficently old that it listed the American morse code (now obsolete) rather than the newer, international code (what is in use today). Contained details on constructing radio receivers, telephones, a carbon microphone that was "sensitive enough to detect the footsteps of a fly" as well as many neato things to do with high voltage. In one experiment they hooked the homemade microphone in series with the primary of the spark coil and a battery. The instructions clearly state you are to tighten the adjusting screw on the vibrating points so that they cannot move, else a 'cruel surprise' would result (soon you'll see why!) Next, a volunteer (victim?) stood while an assistant on each side placed one hand over the volunteers' ear. A thin sheet of paper was placed between the hand and the ear. Each assistant was given a wire from the secondary of the coil to hold. The effect was supposed to be that the volunteer in the middle would hear the voice of a person speaking into the microphone. If the vibrator on the end of the coil began to work what would they hear? =:^o Sorry for the rathole in sci.chem.... Lee
mac@harris.cis.ksu.edu (Myron A. Calhoun) (08/11/90)
In article <872@massey.ac.nz> GMoretti@massey.ac.nz (Giovanni Moretti) writes: >And how about batteries with household chemicals (ie not sulphuric) Almost 30 years ago my senior electronics lab project included a one-transistor amplifier powered by what my write-up called a "P" cell. I recall that it used a silver dime (yep, this was pre 1965), a copper penny, a piece of ink blotter, and a couple drops of urine (hence the name "P" or "Pee" cell!) Worked like a charm. --Myron. -- # Myron A. Calhoun, Ph.D. E.E.; Associate Professor (913) 539-4448 home # INTERNET: mac@harris.cis.ksu.edu (129.130.10.2) 532-6350 work # UUCP: ...{rutgers, texbell}!ksuvax1!harry!mac 532-7004 fax # AT&T Mail: attmail!ksuvax1!mac