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Re: Annonymous


 
1/9/2003 7:32 PM
anonymous Re: Annonymous
quote:
"Sure, hang a 9V zeener off the output of a 12V "wall wart" power supply and tell me how long it takes before the zeener shorts and takes the transformer with it."
 
 
You mean zener, I guess.  
The answer is – it won’t if you size it correctly.  
 
quote:
"Your reference to zeener voltage reduction in an amplifier power supply has nothing to do with the zeener regulation application the original poster is referring to. "
 
 
You mean zener, I guess.  
The original question refers to dropping voltage, not regulation.  
 
quote:
"In one application the zeener is in series with the supply, in the other it is in parallel."
 
 
You mean zener, I guess.  
I gave reference links for both applications.  
I gave no design info.  
 
quote:
"Can you figure out which is which, and why the parallel arrangement will burn out unless a series resistance is added to the circuit?"
 
 
You need to read a little about electronics dude. Are you certain there is no resistance in the circuit now?  
 
quote:
"Please try to give information only when you know what you are talking about. Hiding behind an annonymous lablel doesn't help your credibility any."
 
 
Credibility has nothing to do with it.  
I provided 2 links that give all the credible references required for either the series or parallel application. I provided no design info so blow your comment out your ass.  
As I also said - do a google search on "zener regulator" and fill your boots with credibility. You guys with the anonymous sensitivity and no electronics knowledge are really boring. This is a 500 ma wall wart. If you can't figure out how to size a zener for that circuit, you should back away from the keyboard.  
 
quote:
"As a low voltage positive regulator the three terminal 7809 (7909 for neg. reg.) is far superrior to a simple zeener arrangement, however 12V input is on the low side to insure good regulation at 9V output. These reg's will "drop-out" if the input voltage is within 2 volts or so of the output voltage, causing hum and noise."
 
 
You mean zener, I guess.  
The min Vin for a 7809 is in the order of 11.5 V. Using it here is a dumb idea. What with line supply fluctuations - It probably just won’t work.  
 
BTW get some help with the spelling thing.
 
1/9/2003 8:54 PM
Mike
email

More info...There is a 13V zener, 470uF cap, and a 1200 ohm resister across the output of this adapter. Yesterday, I was getting a solid 13.0 volts(no load) for the few minutes I was checking (didn't check the wall voltage). Today, I'm getting a fluctuating 12.1v with or without the zener in the circuit which leads me to beleive it is indeed some sort of over voltage protection...It seems to me swapping in a 1W 9v zener/resistor combo for the 13v zener would do the trick. And if that is correct, what size resistor would I need?
 
 
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1/10/2003 12:56 PM
Bernt
email
Zener
Mike!  
Experiment!  
If if everything is connected the way I think; just swap in the 9.1V Zener, and see what happens. Flames, smoke or a funny smell is a bad thing ;). The value of the resistor depends on how much current you need; if there's a 1200 ohms series resistor, I really doubt you can get that 500mA in the first place.  
Regards, and report back, Bernt.
 
1/10/2003 1:03 PM
Mike
Thanks, I will. The 1200 ohm resistor isn't in series, it's in parallel with the 13v zener and a 470uF cap which is across the output. There is some sort of inductor or choke in series with the zener/cap/resistor network, I assuming that also provides a small resistance for the zener. Now, I need to find somewhere local to buy a 9.1 zener...
 
1/10/2003 3:35 PM
MBSetzer
email
Re: Annonymous
*If you can't figure out how to size a zener for that circuit, you should back away from the keyboard.*  
 
I think I understand this and it seems to represent the kind of attitude you see on usenet which Ampage was originally intended to provide an alternative to.  
 
Back then I think the unanimous consensus on Ampage would be to advise the poster to back away from the workbench and pull up a chair at the keyboard.  
 
Times have changed but there are still enough Ampagers carrying on the traditional attitude that it continues to make it great, even though when the opposite attitude appears it makes it less great.  
 
I guess a factor might be whether a poster is willing & able to contribute to greatness, surely some who are capable do not have a character which would allow them to strive for that high of an objective.  
 
Mike
 
1/10/2003 4:04 PM
Jakob Erland
Be sure, at least, that the series resistance of the inductor is around 6 Ohms. This would sink 3V at 500mA. If it's less than that, you could easily damage your Zener.  
 
Zener dies two ways:  
 
- Shorting potentially also kills your transformer  
- Open-circuit'ing potentially also kills whatever gadget the power is ´connected to  
 
(..please help keeping the tone a bit more kind in this nice forum..)  
 
Jakob Erland
 
1/10/2003 5:41 PM
anonymous
Striving always and only for greatness and putting on my kinder, gentler more informative hat - excuse me while I have a spoonfull from my bowl of wood and a sip from my glass of mud - I'm very earth friendly, you know (I'm gonna hack off two cylinders from the engine in my car tonight):  
 
I'm terribly sorry to inform you that this calculation appears to be in error - although I'm also certain that it results from no fault of anyone on this forum, although it could be my fault if everyone agrees that this is an appropriate action to take. Maybe "action" is too strong a word to use so I apologize right now about that before anyone pitches a fit and starts a new thread over it.  
 
Just punch in the numbers:  
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/zenereg.html#c2  
 
If you are really pleasant to the guy behind the counter of your local electronics supply shop, you may find that a number of zener diodes are available and with sufficient power rating to yield an appropriate factor of safety to overcome any risk associated with zener device failure. In fact, you may find, if you can do the calculation, that there is a greater risk of alien abduction for anyone who might worry extensively about such risks (put your tinfoil hats on folks). Now if you can’t do the calculation, I in no way mean to imply that you are stupid or anything and you should feel free to start up another thread berating me for even bringing the subject up.  
I’m terribly sorry for posting; I’m shamefully, shamefully too sexy for my own good.
 
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