fred_gomez
20 posts
Jan 02, 2013
8:28 AM
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in an old tube amp if the electrolytic can has a 50-150v, a 40-150v, and a 10-150v, can i replace it with just one modern cap at 100-450 volts? also if im using just battery power can i bypass this cap all together somehow?
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Greg Heumann
1917 posts
Jan 02, 2013
8:54 AM
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It is 3 discreet caps. You can't replace it with one. It isn't about the voltage, it is about the capacitance required at each of those 3 places in the circuit. There is nothing wrong with going to 3 discreet caps of the same capacitance as the originals but rated at a HIGHER voltage (in fact 150V sounds suspiciously low to me for a tube amp).
If you're using battery power? Do you have a battery that makes 250VDC or more? That's what tube amps need - sometimes as much as 600V. IF you had such a battery you could replace the entire transformer/rectifier/filtering caps section (Oh, and your battery would need a center tap because most (for example) 500V circuits are set up for -250V 0V +250V reference.) But you'd also lose tone, because the voltage sag inherent in the power supply on transients has something to do with the amp's tone.
I don't mean to offend but your questions do suggest a lack of familiarity with analog electronic design. You need to be VERY CAREFUL. High voltages run around inside tube amps, HIGHER than what comes out of the wall, and in the form of DC which is much more dangerous (both can kill you, DC kills you easier/faster). And those voltages PERSIST inside the circuit's capacitors - for hours or even days - after you've switched off and unplugged. Please be careful.
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/Greg
Last Edited by on Jan 02, 2013 9:08 AM
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fred_gomez
21 posts
Jan 02, 2013
9:51 AM
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its a tube radio 15 watts, no transformer. the frame is 90 volts the tubes are 7.5 but 4 D cells will make them work. can i just leave the elctrolytics? if im not plugging in a wall? and no i absolutely do not know what i am doing. but then i change wall switches and plugs live. i have been zapped alot i dont think i can really die from electricity.
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tookatooka
3164 posts
Jan 02, 2013
9:47 AM
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Just a quick interjection about using multiple caps just in case someone wants use multiple caps to get to the correct value of capacitance.
10uf in series with 10uf will give you 5uf
10uf in parallel with 10uf will give you 20uf
It's the opposite to how resistance is calculated.
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Tonyh
57 posts
Jan 02, 2013
10:11 AM
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I'm with Greg on this one. The DC voltage in these amps is not at all the same thing as the 120/220V AC you can get from the wall.If you get zapped by AC wall voltage it just hurts a little. DC might kill you ( early models of defibrilator were as simple as big and high voltage dc capacitors discharging)
So....DC is very very dangerous at these high voltage. Learn how to discharge the capacitors safely before working in this amp. You can easily get killed if you don't take precaution. In doubt just ask an amp repair technician in your surrounding. If you take the precaution it can be very rewarding to learn how to work on your own amps.
Last Edited by on Jan 02, 2013 10:14 AM
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fred_gomez
22 posts
Jan 02, 2013
10:30 AM
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well i have a parts list this is all chinese to me i cant find anything on ebay. if the radio doesnt hum on DC power should i just leave the paper electrolytics?
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SuperBee
790 posts
Jan 02, 2013
12:30 PM
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Guys, Fred said the radio runs on 4 D cell batteries. That's like 6 volts dc.
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fred_gomez
23 posts
Jan 02, 2013
1:38 PM
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no theres a A and B battery. 6 volts for the tubes to light up and a seperate battery i made with 10 9 volt batteries in a series. so it works on 90 volts and 6 volts and the preamp is another 9 volts. its pretty loud with a bullet. the preamp will get louder with 15 volts. but its all paper capacitors i dont know what im doing ill just keep messing until something blows up. but i read if the radio hums it means the electrolytic caps are going bad. when i switched to all dc power it stopped.
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jimbo-G
144 posts
Jan 02, 2013
1:47 PM
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Fred electricity can kill and i strongly advise you not to mess around with high voltages until you can respect the dangers involved.
The capacitors are in the circuit to smooth out the signal so bypassing them is not really a good idea. i could be wrong but the reason tube amps need high voltages is because when the very small signal generated from an input is sent to the grid it gets relayed onto the high voltage flowing through the valve . like if you put your hand infront of a projector your hand is the grid and the screen and projector is the anode and cathode, you see a larger shadow of your hand on the screen thus amplifying it.
When the radio hums it can be that the capacitors are drying out or near death.
Try downloading some old valve books. A very good resource is http://www.tubebooks.org/technical_books_online.htm
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5F6H
1468 posts
Jan 02, 2013
2:04 PM
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There are lots of causes of hum (bad layout, poor heater/6v filament circuit design...which is what your symtoms posibly point to - dc heaters are often a band-aid fix in curing shoddily built amps of hum, single-ended amps often hum because the output section is not hum cancelling like a push-pull amp), electrolytics go bad all the time with no obvious hum...low B+ voltage, mushy response, billowing smoke & blown fuses are better signs of dead filter caps.
"i dont know what im doing ill just keep messing until something blows up" Why not cut out the middle man? I recommend some C4 if you just want to blow things up! ;-) On the other hand, if you want to play music though it, take it to a tech. If you feel confident in doing the work yourself (your posts so far don't show that you have a basic understanding of the circuitry) post some pics and/or try and draw up a schematic.
When AC powered does the amp run straight off wall AC? Does it have a power transformer? If it does not have a power transformer, don't use AC power mode.
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http://www.facebook.com/markburness
Last Edited by on Jan 02, 2013 2:06 PM
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ElkRiverHarmonicas
1462 posts
Jan 02, 2013
3:42 PM
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Be careful. Don't believe that Thomas Edison B.S. hype about DC being so safe babes could suckle on it or whatever. Be very careful.
It is also very easy to catch stuff on fire. One little hair strand of solder, so tiny you can't see it, can set the board ablaze. Be careful.
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David
____________________
At the time of his birth, it was widely accepted that no one man could play that much music so well or raise that much hell. He proved them all wrong.
R.I.P. H. Cecil Payne
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David
Elk River Harmonicas
 
Last Edited by on Jan 02, 2013 3:43 PM
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fred_gomez
24 posts
Jan 02, 2013
6:40 PM
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well this circuit bending thing is kinda like a new fad, making guitar amps from old transistor radios. but nobody is doing tube amps and especially DC powered tube amps. there is no transformer at all. i did plug in the wall when i got it turned the plug around to reduce the hum. i was told it was just line noise. there are no fuses none whatsoever. it was hard to figire how to hack into it so i could kill the radio and plug a mic or guitar in. i sorta just plugged it in the wall and messed with aligator clips till i found what worked best. man you shoulda seen the sparks fly! im surprised it still works so well. i put the radio in a bigger box and added a bigger speaker. but its really cool, id like to keep it. i cant afford to send it to an old radio guy and have it recapped. i only paid like 10 bucks for it. shame it sounds really great way better than a solid state 15 watt amp.
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Jim Rumbaugh
810 posts
Jan 02, 2013
7:32 PM
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WARNING
DC voltage can kill
AC amps with no power input transformer are dangerous to touch.
Now back to your question.
I agree that batteries could get rid of most of the hum. The MAIN purpose of those capicitors is get rid of the AC ripple (hum/audio) and give the circuit a pure DC power source. An old designation of A,B,and C size batteries were
A = filament
B = highvoltage a.k.a B+
C = bias.
link to supporting info
http://en.wikipedia.org/wiki/Battery_(vacuum_tube)
If your voltage is too low, it will probably still work, it just may sound funny. But then, a lot of the resistor swapping you read about in amp circuit mods is to cut the voltage down.
About replacing the capacitors. You can replace with larger values, as already mentioned in other posts. IF you are running off batteries, you probably don't need the first cap off the rectifier, the other 2 should be used, but it MAY work without then too.
Just be carefull, don't do something stupid. Keep it up and you may become an expert someday.
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theharmonicaclub.com (of Huntington, WV)
Last Edited by on Jan 02, 2013 7:45 PM
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Boof
1 post
Jan 02, 2013
8:21 PM
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Fred, Sounds like what you have is an old AC/DC radio. These ave very dangerous when run on AC line voltage as the chassis on many of these radios had one side of the AC going directly to the chassis or had the chassis grounded through a capacitor to one side of the AC.This is very similar to the Death Cap on many Fender amps that switches a cap from one side of the AC to the other to reduce hum, like when you reversed the AC plug. As these caps get old the can short out and put AC voltage directly to the chassis, hence Death Cap. There is no easy and inexpensive way to make this amp safe.
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Greg Heumann
1919 posts
Jan 02, 2013
8:37 PM
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I agree with Jim "I agree that batteries could get rid of most of the hum. The MAIN purpose of those capicitors is get rid of the AC ripple (hum/audio) and give the circuit a pure DC power source."
However you need to know that 90VDC CAN KILL. Even from daisy chained 9V batteries. It can stop your heart. You are playing with fire, Fred.
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/Greg
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fred_gomez
26 posts
Jan 02, 2013
9:59 PM
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ok heres the spec sheet
electrolytic capacitors
C1 A 80-150 VOLT
B 60-150 VOLT
C 250-10 VOLT
fixed capacitors
C2 .47-200 VOLT
C3 47
C4 5
C5 10000
C6 100
C7 .22-100 VOLT
C8 .47-400 VOLT
C9 10000
so what am i supposed to get? also you mean my homemade 90 volt batter coulda set the airplane on fire? and tsa didnt see this?
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jimbo-G
145 posts
Jan 02, 2013
11:29 PM
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I would just replace the dead capacitors and get the circuit back to its original working state. Then draw out the schematic and figure out what is really needed for only the amp part, using the schematic not poking around with a meter. A easy way to hack into old radios and such is to connect the core of your guitar cable to the wiper pin on the volume pot and earth the shield. This is maybe not a good idea if your chassis is live.
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fred_gomez
27 posts
Jan 03, 2013
12:02 AM
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yes the chassis is live thats how i did it. the caps arent dead everything works 55 years later. i dont have a meter. i discharge the caps with a light bulb? the hum is totally gone with DC power. i have the schematic i cant understand it.
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jimbo-G
146 posts
Jan 03, 2013
12:31 AM
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If it works just use it, it probably won't last very long but Atleast it wasn't expensive and you can get some use from it, just be carefull and not fry yourself. Can you post a pic of the schematic it could be nice to see.
Edited to say get a meter, it could save your life.
Last Edited by on Jan 03, 2013 12:33 AM
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ElkRiverHarmonicas
1463 posts
Jan 03, 2013
1:31 AM
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On the AC hum. Did you ground the ground?
You ought to check the value on the resistors, too.
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David
____________________
At the time of his birth, it was widely accepted that no one man could play that much music so well or raise that much hell. He proved them all wrong.
R.I.P. H. Cecil Payne
----------
David
Elk River Harmonicas
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5F6H
1471 posts
Jan 03, 2013
4:52 AM
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@ Fred Gomez "the hum is totally gone with DC power. i have the schematic i cant understand it."
This is not unusual, it is not a sure sign that the electrolytics are to blame. I suspect it may be a filament issue...possibly exacerbated by other things.
Post the schematic, you are welcome to e-mail it to me.
Do not use the amp when plugged into the wall, without a 1:1 isolation transformer, one fitted with a fuse. You chassis is hot, if something blows and puts wall voltage through the chassis, it will go through you too because you are holding a mic that has the shell attached to the chassis. These kinds of amps are illegal to construct nowadays in most developed countries.
The filter caps are dead...the light might come on, sound might come out, but they are not right. Coupling & tone caps may or, may not be good, it's probably not necessary to change every cap in the amp.
Again, take it to a tech, or stop futzing with it until it is safe & you are sure it functions correctly. It's purpose is to make a nice sound when you play through it, it's not going to do that if you kill it...it's not worth risking the amp, or your safety, for a few minutes of fairly pleasant squawking before something gives and you get full, unprotected, wall AC voltage accross your chest!
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www.myspace.com/markburness
http://www.facebook.com/markburness
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fred_gomez
28 posts
Jan 03, 2013
9:33 AM
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no no ground from what ive read, the hum is caused by line noise (other appliances in the house) in the 50s people didnt have alot plugged it at once, so when you use battery power the hum is gone. from what i understand if it hums loud dont touch the screw to the chassis. flip the cord around then you can touch the chassis. but i dont plan on using AC current at all in fact im gonna cut the cord its gettin on my nerves. thre is no indicator light this is 50s no leds you look at the tube to see if its on. i cant see a diode or an antenna anywhere. i have the black line aligator clipped to the chassis. this allows me to use it as a radio if i unclip it. i guess if i put a fuse of some type on that line? ok this is what i figured out and i know im probably wrong.
ELECTROLYTIC CAPACITORS (CAN)
C1A 100UF 160 VOLT
C1B 68UF 160 VOLT
C1C ???????
FIXED CAPACITORS
C2 .047UF 630 VOLT
C3 0.047 630 VOLT
C4 0.005UF 630 VOLT
C5 (CERAMIC/MICA STAYS)
C6 0.1UF 630 VOLT
C7 0.22UF 630 VOLT
C8 0.47UF 630 VOLT
C9 C5 (CERAMIC/MICA STAYS)
from what ive read the elctrolytics are only for the AC line. on the schematic the only electrolytic shown on the DC line is C1C the one with ????? which says 250 mmfd 10 volts i cant figure the modern equivalent of that.
but no i made up my mind it sounds too cool to waste, the tweed case i put it in has nice acoustics and the 8 inch speaker and the 3 watt preamp sounds great. so i guess the next step is go cap shoppin and back to playin with fire. sorry man i dont have a scanner, i would have to photo copy the schematics and snail mail them to you.
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FMWoodeye
522 posts
Jan 03, 2013
10:37 AM
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I was already apprehensive about doing even the smallest bit of work (changing pre-amp tubes) on a couple of my amps. Now I am more so. I have visions of a tow truck winch dragging my dead fat ass up the basement stairs. Would I be correct that if the amp had been unplugged for a couple of weeks, it would then be completely safe?
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jimbo-G
147 posts
Jan 03, 2013
11:39 AM
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@fmwoodeye, capacitors can hold a charge for a long time depending on the size, current, charge, ect.. I would always make sure there was no killer juice left in before touching them.
@Fred, you will need to put a sound sample up if you survive, I love the sound of an 8 in a tube amp.
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5F6H
1472 posts
Jan 03, 2013
11:51 AM
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@Fred Gomez - When an amp hums, you fix the hum, if you can. Many amps do not hum appreciably, no matter what else you have on in the house...you are not reading stuff from credible sources.
"i have the black line aligator clipped to the chassis. this allows me to use it as a radio if i unclip it." What black line, please explain?
Electrolytics are always in the dc parts of the circuit (rectified B+, cathode bypass, negative dc bias supplies), they're just caps, you can replace them with any other kind of cap if you can find one small enough...have a look at a 100uf 500v poly cap if you can find one, or a 250uf poly cap of any voltage rating and you'll see why electrolytic caps are popular in mass produced amps, some expensive musical instrument and hi-fi amps have no electrolytic caps at all. However, there is AC just about everywhere in an amp, riding on the dc...there has to be, it's what makes your transformers & speakers work.
250uf 10v - 220uf at anything over 16v will do the job. They are very common.
"3W preamp" no it isn't. Preamps are voltage amplifiers, boosting & shaping the signal so it can drive the output section, which IS rated in Watts.
C2 to C9 only need replacing if they are leaking...leave them for now.
C1A, C1B & C1C should be replaced by discrete caps, C1A should be grounded to where the cap can is grounded (you might be able to sever the leads & keep the can in place, just not wired up)...I can't say where the others should ground without seeing it...250uf sounds like a cathode bypass cap, could be on the preamp or the power amp cathodes though. The positive ends of these caps go to prescribed points, you can't replace 2 caps with different functions, with one cap, looks like one is for the power tube plates and the other for the preamp, possibly a triode power tube?
If you are never going to use AC then remove the AC cord.
my e-mail is: markwjburness at btinternet dot com
e-mail me and I'll give you my postal address.
@ FM Woodeye - Your amp is perfectly safe as long as you don't go poking about in it's guts, so long as the tubes are cool to the touch and the amp is turned off & unplugged from the wall anything external should be safe, don't go poking conductive materials in empty tube sockets though.
No, your amp is not safe if it has been unplugged for some time (have had holes burned through my skin -through my own careless fault, in normal use amps are safer than laptops & Blackberrys - by shocks from amps that haven't been used for months!), it is safe when the caps are drained and will remain safe if the drain is kept in place, until you are ready to power up again. I use an insulated jumper lead from the chassis to a preamp tube plate pin (amp unpluggd from the wall) this drains the caps in about 30 seconds, all the time the jumper is there, the caps won't recharge. Some amps have bleeder resistors that will drain the caps for you, I would need to know model & make of amp before suggesting whether this is pertinent you/your amp.
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www.myspace.com/markburness
http://www.facebook.com/markburness
Last Edited by on Jan 03, 2013 12:41 PM
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jimbo-G
148 posts
Jan 03, 2013
12:14 PM
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@5F6H, you are a knowledge explosion, I love it.
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Kingley
2104 posts
Jan 03, 2013
12:27 PM
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Fred - From reading this thread it would seem that you're not really sure what you're doing when working with electronics. Please listen to Mark (5F6H) and Greg. Those guys really know there stuff when it comes to amp circuits. Please, please, please DO NOT work on this amp if you aren't knowledgeable about electronics. The voltages in these amps CAN KILL YOU! It's not worth risking your life trying to get a good sound out of an amp. My advice would be to send it to an amp tech. If you can't afford to, then save up and wait until you can.
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fred_gomez
29 posts
Jan 03, 2013
1:04 PM
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ok the black line. i have my bullet plugged into a jack. the jack is connected to this http://www.amazon.com/Velleman-K8066-3W-MONO-AMPLIFIER/dp/B001VCL6I6
then the 3 watt velleman output goes redline to the volume knob the black line to the metal radio chassis. this cancels out the am radio and it becomes an amp. without the velman it works but isnt very loud. theres a 4" speaker on the radio i aligator clip that to a bigger 8" speaker, so two speakers work. if i wanna be quiet and practice i disconnect the big one.
nothing at all is leaking. the reason these radios still work is because people bought them to listen to one baseball game while fishing. the batteries didnt last long and were very expensive. it says on the radio its suggest yoy use the radio with battery power. obviously people got killed by radios then. so people usually put these in a closet and saved them. you can find them in cherry condition. btw what is a dicrete cap? ok 5f6h i will give you a write
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5F6H
1473 posts
Jan 03, 2013
1:23 PM
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Discrete cap is just a single part, one individual cap doing the job of one of the can cap sections. Can cas were used for convenience when assembling lots of amps, cap companies would custom make cans. Som great amps still use can caps, or a mixture of both cans & axial caps, but the grounding design is usually better than budget amps, where all the grounds met at one, arbitrary point.
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Boof
2 posts
Jan 03, 2013
2:22 PM
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I feel a little better (but not a lot) that you are using the Velleman amp as a preamp. This may give you some issolation of the Microphone form the radio chassis. Take an Ohm meter and measuer resistance from the ground/ Shield of the mic to the chassis of the radio. Make sure that the radio is off. If it measures amything below 1 Meg ohm you still have an electrocution device especially if it reads 0 ohms. A good way to gurantee isolation between the Velleman and the radio is to use an output transformer hooked up, with the speaker output of the Velleman connected to the 8 ohm side of the transformer and the other side of the transformer connected to the volume control of the radio. Any inexpensive output transformer should work. It will also give you the correct impedance match between the Velleman and the radio and should improve the sound quality and gain.
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fred_gomez
30 posts
Jan 03, 2013
4:36 PM
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ok where do i find one of these transformers in the trash? the radio was 10 bucks , tweed case trash,8" speaker trash, velleman a gift (3of them). 20 bucks for the 9 volt charger, 20 bucks for the batteries. im not putting any money into this what trash wise would i be looking for? please say its inside a printer lots of those in the trash. oh and my sheild for the velleman is a cigarette celophane and masking tape. again im not plugging this into the wall. ive broght it and my homemade batteries through customs many times no questions asked im really glad to know now it can set on fire at any time and am now not storing batteries in it. i guess for now i will have to make a mic with a plastic housing, a plastic phone speaker and a rubberized guitar plug end thingy. and stop using the metal bullet. maybe a 100k vc on it too.
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ElkRiverHarmonicas
1464 posts
Jan 03, 2013
5:33 PM
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OK, I gotta say something here.
The stuff of "don't work on this amp, because you don't know anything about electronics" stuff, I'm not necessarily in agreement with. You gotta learn sometime and this is a teaching moment from now on for us.
There was a time when I worked on stuff for the first time.
Remember:
1) for God's sake don't work on it when it's plugged it or has a battery.
2) A short can start a fire in the circuit. I mean a real fire. They are always a surprise.
3) a cap can shock you even if it's not plugged in and has no electricity to it.
At this point, he knows the risk.
Now, if you're gonna do this, for God's sake do it right. By that, I mean, do it so that when you are done, you have something work having.
Fred, tell me, what is specifically wrong with the circuit. This is all over the place in the thread, I'd like a little list of specific problems and we'll address them.
On the ground thing, what I was getting at is that you need to ground this. Radio signals induce an creates AC current in the antenna. What the radio does is first convert nature's (and radio is a natural phenom) AC current to DC. Then, you have variable capacitors that filter out all the frequencies except the one you want - because when it comes in on the antenna, it's ALL radio frequencies at the same time.
Then, it changes whatever frequency you want, say 580 kHz and turns it into, I don't know, maybe 1400 kHz. You got to listen to anything, even the Froggy 101 FM, it will turn that into 1400 kHz, or whatever. Even FM radios convert the FM signal into an AM signal on that fixed frequency in the circuit (FM radios are AM radios that translate FM into AM, but I'm getting off subject).
So whatever frequency you are listening to gets turned to 1400 kHz (I don't know what it is) and goes to the amplifier stage. The circuit itself, I mean the actual circuit itself is tuned for picking up signals at that frequency.
You will have resistors going to ground for all these circuits. They will go to the chassis, where this energy is released - a lot of it in the form of radio waves. Grounding the chassis can help this.
Take a three prong electric cord. Ground it. It will help.
Everything can and should be grounded. You ought to see what grounding Nikola Tesla was doing. Only Tesla could make grounding stuff sexy and badass.
If you wanna learn jerry-rig electronics like this, get some of the project books they had for kids back in the 1920s and 1930s. That was back before any thought of suing somebody if they died and you can learn all sorts of stuff.. not the two or three useful sentences peppered across 40 pages of "You'll shoot your eye out!" like today. Those are really great for learning how to take stuff from other stuff. Those people built radios, flux capacitors, who knows out of crap they'd find laying around.
You'd be better off, if you ask me, to build a new circuit, but I will help all I can. Radios are something I know a little about.
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David
____________________
At the time of his birth, it was widely accepted that no one man could play that much music so well or raise that much hell. He proved them all wrong.
R.I.P. H. Cecil Payne
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David
Elk River Harmonicas
Last Edited by on Jan 03, 2013 7:02 PM
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SuperBee
791 posts
Jan 03, 2013
7:28 PM
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I wonder what billy shines would have had to say about this, or professor blues. Pffft!?
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fred_gomez
31 posts
Jan 04, 2013
5:47 AM
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well forget the plug im not using it. its got to be plugged in an interior socket to switch over to battery mode. im keeping it battery. so how would i ground this, screw a chain to the chassis and screw the other end to the root of a tree? i dont have metal pipes here. the spec sheet says dummy antenna. i dont see an antenna , transformer, or a diode anywhere. as for the radio it works fine as an amp, some reverb would be nice later one. but i was told if i didnt replace the paper caps disaster lurks around the corner. i looked into russian new old stock paper caps of the same exact values but heard those are deadly dangerous too. i can mail you a photo copy of the schematic if you like radio stuff. its got to be simpler than it sounds to be made like this. and i know it sounds strange.
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5F6H
1474 posts
Jan 04, 2013
6:41 AM
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You wouldn't use NOS electrolytics, they normally degrade faster if left on a shelf.
The electrolytics (C1A, C1B, C1C) are not paper, they are aluminium cans, they may be covered with card as an insulation & somewhere to write the specs. Nowadays they are covered with shrink film.
Paper foil & oil caps are used as coupling (AKA blocking) caps and tone caps.
With battery power why would you need a diode? These are normally used to rectify AC into dc?
Is there no output transformer, the secondary leads would run to the speaker?
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lor
171 posts
Jan 04, 2013
7:14 AM
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Mr Gomez - the stand up forum comedian! Got all techies jumping.
(Even me: Fred, capacitors don't do anything with voltage except burn up if it's too high (bigger numbers mean more voltage). But it's not all about voltage, the real thing is current = amperes. That's a measure of real stuff - electrons moving in the wires. Voltage is only the pressure difference between the ends of the wires, the pressure that makes the electrons move and become current. If one end of a wire has more electrons available than the other end, some of those electrons will bump others down the wire until there's the same number at each end. That motion is current, measured in amps, and it's Direct durrent. Voltage is basically just the degree by which one end's supply of electrons exceeds the other end's supply. AC current is when the mechanism is setup so the difference in supply keeps switching from one end to the other, and the current changes direction with each switchover. Often there's a basic DC amount maintained while an AC part is added to the wire. Capacitors block DC current while passing AC current (sound wave signals) because the electrons can feel the presence or lack of presence of other electrons nearby on the other side of the insulating barrier inside the capacitor. If the voltage is too high it sparks through the insulator and wrecks the capacitor.
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ElkRiverHarmonicas
1465 posts
Jan 04, 2013
10:52 AM
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You're not going for historical accuracy here obviously, there is no need to use paper caps. That's the only reason you ever would. Modern caps will work and are what you should use, provided the values are applicable.
Dummy antenna? Really? A dummy antenna is an antenna (usually built inside something that looks like a paint can it's an antenna that is small dissapates heat and is used to test transmitters.
Did this radio originally run on AC? I'm thinking you just solder AC wires to the transformer. Is that not the case? I would like to see the schematic.
Idon't have metal pipes either. I'll tell you what I use for a ground - a grounded electrical outlet. It's not the best ground for non-noise, but it's better than nothing. My receivers are connected to a ground terminal, which is connected to a modified extension cord. This cord has the AC plugs removed. There is only the ground plug and wire. I just put it in the ground of a plug-in strip, which is connected to a wall socket.
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David
____________________
At the time of his birth, it was widely accepted that no one man could play that much music so well or raise that much hell. He proved them all wrong.
R.I.P. H. Cecil Payne
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David
Elk River Harmonicas
Last Edited by on Jan 04, 2013 10:52 AM
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CarlA
224 posts
Jan 04, 2013
11:57 AM
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I hope this whole saga has a happy ending, because so far??!??...........
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Boof
3 posts
Jan 04, 2013
7:22 PM
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The best place to find an output transformer would be from an old tube radio. The transformer is sometimes attached to the speaker. The transformer you are looking for has one side connected to the speaker. You could even scrounge a transformer from an old transister radio that had an output transformer. Newer transistor radios usually dont have a transformer. Being an old parts scrounger myself I am always looking for these things at swap meets trash cans yard sales etc.
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Greg Bouffard
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fred_gomez
33 posts
Jan 04, 2013
7:48 PM
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yeah i saw the same radio for sale only this one did have a transformer on the speaker exactly as you said. but it was too much and didnt work plugged in.
i found this today
http://www.youtube.com/watch?v=cJuGx3lLpMo&list=UU0XOfaGXmyT7D-FvR07OakQ&index=43
still dont know what im doing oh well here goes nothin!
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