EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: kungfu-pegasus on May 22, 2015, 06:52:10 am
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Hi there i have a roberts radio model RFM3 and i changed the polarity of the dc jack to + in middle ad - out side as normal then i plugged in a 1500 Ma 9v charger and it blew the radio somehow as it doesnt power on now
i checkec the orginal charger and it was 500Ma 9v i have taken pictures of board can someone please give me an indicationof what could have blown please the radio does not power through jack or battery terminals anymore
cheers
also attached schematics which i found in net
Pictureshttps://flic.kr/s/aHskbVzKjC (https://flic.kr/s/aHskbVzKjC)
p.s i am a total newb but i am wiling to do the work
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You can't "put to much current in", a device will _draw_ whatever current it needs.
Looking at the schematic, that's a 3 wire switching jack, so my guess is you've created at short when trying to change the polarity...
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superb so where do i start guys ?
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well your in for a fun time, seeing as the circuit had no diode... (seriously WTF?) first thing i would do is grab a multimeter and make sure that the power inputs when switched on are not shorted together, (e.g. blown cap or chip).
diagnosis steps,
test that 9V is at the plug before switcihg on, (battery removed, and correct polarity)
switch on
see that your voltage is still there, and that it is not heavily pulled down
if ok, next up, lift out the potentiometer that connects the lower op amp to the top one, and inject a signal to the top one, see if this gives any response on the output (this will verify is that chip works)
if ok, then replace the pot and turn your attention to the bottom op amp,
that should be enough to cover you for a while, and install a diode in the positive connection to the board if you can,
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oh shit did you just speak chinese?
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oh shit did you just speak chinese?
Are you sure you're in the right place?
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what do you mean i am in newb section and the geezer speaking to me like i am a pro
can i have it explained to me a bit better i am a total newb for petes sake
and yes i thought i was in right place new section...
are u ?
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A beginner in electronics typically owns at least a multimeter and a soldering iron. If you are such a "total newb" that you don't own either, or understand what a diode, a potentiometer or a capacitor are, you probably won't get far trying to repair a fried radio.
Perhaps you could describe your level of experience in a little more detail so that prospective helpers know where to pitch their explanations?
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Have you also rewired the switch contact of the DC jack for the battery? If so, how?
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A beginner in electronics typically owns at least a multimeter and a soldering iron. If you are such a "total newb" that you don't own either, or understand what a diode, a potentiometer or a capacitor are, you probably won't get far trying to repair a fried radio.
Perhaps you could describe your level of experience in a little more detail so that prospective helpers know where to pitch their explanations?
Does the OP even know what a multimeter is...? ::)
Given that he found schematics he should also be able to look up what those terms mean.
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what do you mean i am in newb section and the geezer speaking to me like i am a pro
can i have it explained to me a bit better i am a total newb for petes sake
and yes i thought i was in right place new section...
are u ?
Basically what he is saying, in layman's terms, is it's buggered, if you don't know one end of a soldering iron to the other then buy a new radio.
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Hi there i have a roberts radio model RFM3 and i changed the polarity of the dc jack to + in middle ad - out side as normal then i plugged in a 1500 Ma 9v charger and it blew the radio somehow as it doesnt power on now
i checkec the orginal charger and it was 500Ma 9v i have taken pictures of board can someone please give me an indicationof what could have blown please the radio does not power through jack or battery terminals anymore
cheers
also attached schematics which i found in net
Pictureshttps://flic.kr/s/aHskbVzKjC (https://flic.kr/s/aHskbVzKjC)
Looking at the pictures and schematic, you can see that the coaxial power jack has three wires on it, so that the internal battery is disconnected when you plug in an external power supply. So, it is quite possible that you re-wired it incorrectly, with at least three possible outcomes:
1) You created an open circuit, meaning that the power never reached the radio.
2) You created a short circuit on the power supply, causing the supply to get shorted out when you plug it in.
3) You reversed the polarity of the power applied to the radio circuitry.
1 & 2 would likely not cause damage to the radio, provide any short circuit didn't cause excessive current to flow to damage wires, traces, etc. #3 could have possibly damaged some components in the radio.
If you are not comfortable using a meter to check your to ensure it is wired correctly, then the repair is likely out of your reach.
Have you tried reversing the change you made, and connecting up a 9V battery instead of the external supply to see if the radio still works?
p.s i am a total newb but i am wiling to do the work
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what do you mean i am in newb section and the geezer speaking to me like i am a pro
can i have it explained to me a bit better i am a total newb for petes sake
and yes i thought i was in right place new section...
are u ?
Please be courteous to someone who has spent time to look at your photos, think about your question, and offer advice for free. If you don't understand what they have said or suggested, courteously say you don't understand and say what your level of experience is. Also, do research on the terms they've used and spend some time to see if you can understand what was suggested (you said you were willing to do the work, right?).
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didn't know 22 years old qualified as a geezer, (watch your tongue you young whipper-snapper :p )
by cap, i mean capacitor, either a tantalum type, or an electrolytic,
http://www.learningaboutelectronics.com/images/How-to-read-a-tantalum-capacitor.png (http://www.learningaboutelectronics.com/images/How-to-read-a-tantalum-capacitor.png)
http://upload.wikimedia.org/wikipedia/commons/8/87/Polarity-wet-Al-Elcaps.jpg (http://upload.wikimedia.org/wikipedia/commons/8/87/Polarity-wet-Al-Elcaps.jpg)
by potentiometer, at-least based on how the schematic is laid out it would be your volume control knob,
This is what i mean by a multimeter:
http://www.jaycar.com.au/medias/QM1323ImageMain-300Wx300H?context=bWFzdGVyfGltYWdlc3wyOTU3NHxpbWFnZS9qcGVnfGltYWdlcy9oODYvaGU4Lzg4MTUxOTg3NjUwODYuanBnfGM0YWJhODlhNjc5NTNlMDYwODhmMTU1OGExNWQ5ZjZmZjhkMzIwYWI0Nzk5ODk4ZWNkOWU2YjU1MjUyODdmOTc (http://www.jaycar.com.au/medias/QM1323ImageMain-300Wx300H?context=bWFzdGVyfGltYWdlc3wyOTU3NHxpbWFnZS9qcGVnfGltYWdlcy9oODYvaGU4Lzg4MTUxOTg3NjUwODYuanBnfGM0YWJhODlhNjc5NTNlMDYwODhmMTU1OGExNWQ5ZjZmZjhkMzIwYWI0Nzk5ODk4ZWNkOWU2YjU1MjUyODdmOTc)
Not http://cf.cdn1.zepo.in/upload/product_photos/base/0/18/94/original1.1203731.1.jpg (http://cf.cdn1.zepo.in/upload/product_photos/base/0/18/94/original1.1203731.1.jpg)
and to cover the only other term i think you may get caught on, http://www.allaboutcircuits.com/vol_3/chpt_3/1.html (http://www.allaboutcircuits.com/vol_3/chpt_3/1.html)
Like wilksey said, the thing is buggered, what i TRIED to help you with was working out what piece of it was buggered, to then replace / repair to get it working,
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what do you mean i am in newb section and the geezer speaking to me like i am a pro
can i have it explained to me a bit better i am a total newb for petes sake
Ok then. Take what the gentleman said to you and start dissecting it. When you find a bit you don't understand, punch it into google and see what comes up. That way you can break it down into bits you *can* understand and you'll learn something along the way. The other option is to come back with more questions, but to just say "oh shit did you just speak chinese?" makes you look like a petulant 10 year old who want's to be spoon fed (and they don't get far on this forum).
We all started somewhere, but as with life in general, the key is learning to teach yourself. At least these days you have access to a massive on-line library with information at your finger tips.
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OP sounds like a fine example of the Google generation (http://www.informationweek.com/despite-the-internet-google-generation-lacks-analytical-skills/d/d-id/1063505?)
A study conducted by the University College London found that young people lack analytical skills necessary to assess the information they find on the Internet
While the so-called "Google Generation" grew up with the Internet, having a sizable chunk of the world's information at their fingertips has failed to make them better thinkers, according to a university study.
Young people born after 1993 are certainly familiar with computers and the Web and use both with ease, but a study conducted by the University College London found that they lacked the critical and analytical skills necessary to assess the information they found mostly through search engines.
Gen-G'ers can't think for themselves, even when told how. Rerouter is an exception :)
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The O/P has left the building.
Re-enrolling in Underwater Basket Weaving 101.
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just say "oh shit did you just speak chinese?" makes you look like a petulant 10 year old who want's to be spoon fed
Or a marketing manager
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First thing I would do is reverse what you have just done to the power socket, the radio may still work then on the battery, it is quite possible the only thing that you shorted was the power supply, that depends of course on which of the two wires on the power socket you swapped around but if you are lucky it may well be.