| DD_Davo |
Hi
I built the Velleman K4003 amp and for testing it i'm using two PP3 batterys. When i connect the amp up to speakers and an input it plays ok for the first few seconds then crackles and dies, with the occasional pop and crackle. If i unplug one one of the batteries and wait 10 seconds, plug it back in i usually get another 3 seconds of amplification before it cuts the sound again.
The main IC the TDA1521 gets warm so i presume something inside it is working, but the first time i did it i foolishly put the IC in the incorrect way and put power through the amp (it didn't work), and wondered if i could have damaged it.
If the sound does stay on it tends to crackle unbelievably and you can't make out what the music is.
Do you think it is the IC, which i should replace or could it be something like the capacitors. I doubt the diodes are casusing any problem as there working as a rectifier if i use AC current however i'm using DC.
Thanks for any help |
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| Davide82 |
the problem is with the small batteries you're using.
The 9 volt battery can't give all the power you need, they are simply way too small!
If you want to run batteries, put together some alkaline AA (at least).
If you wait some time unplugging the batteries you let them to "recharge" a little bit (for some reason which I don't explain here) and they can run a for some seconds again.
If what I say is true and you want to test before changing the batteries, you could probably reduce the problem a little putting big capacitors (2200, 4700 uF) in parallel with batteries. |
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| DD_Davo |
Ah ok thanks, well i've been messing with it for past few hours and i got it running ok for 10 mins eventually but when i turned the input volume up it just distored like mad. However i think the IC is probably ok, so if i try a bigger supply. The amp requries a maximum of 4A 24V but i may try and find an old transformer which will deliver 12V at 1A and see if thats any better.
Would you suggest anything inparticular as i don't fancy wiring my own 50Va transformer up.
Thanks |
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| Stocker |
| It's really not that difficult to come into possession of a 24v 4A supply. If you have a 12V 1A wall wart, go for it, but if you are going to spend money, do some more looking. |
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| DD_Davo |
Its a 24V 4A transofmer i can't seem to find, or less i buy just a transformer that i wire up to my circuit, but i'd prefer a plastic encased and tested one, that i could just chop the end of and connect the wires to my PCB.
Thanks |
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| Davide82 |
simple small plastic encapsulated transformers are difficult to find above 12V - 1A. I think it isn't even enough because (looking on datasheet) the chip needs at least +-7,5V which is 15V asymmetrical PSU!
I would buy a symmetrical 12-0-12 transformer and wire by yourself (but pay attention to power line!).
If you don't need the whole power, the transformer has only to be rated for 2 x 1 A (so it is about 25W total: cheap). If you want to go for loud music and better fidelity you can go for larger transformer (say 2 x 3A?)...
You also need, of course, bridge diode rectifier rated 3 A at least and two capacitors about 4700 uF 25V... |
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| Davide82 |
I forgot something:
if you want to go really cheap there's another way: you can get TWO 12 V 1 A cheap wall wart and use them as symmetrical PSU.
It will not sound GREAT but it works, you've only to decide what you're looking for...
Should you choose this way, it would really improve the sound increasing the capacitors in parallel with the two transformers, say 2 x 4700 uF. |
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| DD_Davo |
great thanks, well the amp has a built in rectifer and it has 2 * 4700micro farad capacitors if thats what you mean.
http://www.velleman.be/Downloads/0/Manual_K4003.pdf
That link there is for the manual of this amp, shows the circuit diagram. What i'm after is something reasonably loud with ok sound quality, i realise i won't get the full power usage out of the amp or less i use the 2*12V 2A transformer required (50Va)
Can you explain more about the two 12V 1A transformers please, also what is wall wart transfomers? But if i can buy something cheap thats already wired that i only have to connect to my amp to deliver reasonable volume at reasonable quality that woul;d be great.
Thanks for your help |
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| DD_Davo |
This morning i wired up a 12V Unregulated transfromer and the amp worked fine for about 20 seconds then just cut out again. I think this transformer only delivers about 360ma anyways, so about 1/3 of an amp, but it was working. After thjat though the speakers only emmited the sound of 'flowing current' like an electrical hum, and no audio could be heard.
Do you think it still is power issues or that the IC or electrolytic capacitors have been damaged, i know these capacitors could be damaged if they don't fully discharge and therefore have a 'memory' which cuases them not to function fully next time.
Thanks |
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| Davide82 |
I wonder how you connected the transformer; basically you need two PSUs (or a center tapped transformer) just as written in the manual (you see the two batteries connected?). Of course a normal transformer with only two wires coming out is not suited...
tell me more... |
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| DD_Davo |
well I wondered about that. I ignored the ground, and just connect the + input on the pcb to the + on the trasnformer and the same for the -.
AH so are you saying i should buy 2 12V 1A transformers, connect the - from one tranformer to the - on the PCB
the + from the other transformer to the + on the PCB
and then the remainging - and + from the 2 transformers, join them together and connect them to the ground?
So what i did earlier with the transformer was wrong then? Hopefully i didn't damage anything.
Thanks for the help |
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| Davide82 |
I think you didn't damaged anything...
If you decides to buy new transformer, then buy something quite good! you won't spend a lot buying a transformer that suites the amplifier;
Have a look here:
http://www.maplin.co.uk/Module.aspx...ldID=3&doy=19m3
should you buy and wire by yourself remember to put right fuses and pay attention.
I think buying 2 new wall wart 12V and only 1A wouldn't be cheaper and would be sonically inferior.
You should use two separate transformers only if:
- you already have them and the quality and power you get is enough for your tastes
- you don't want to wire by yourself
If you already have two transforners hanging around even very small (few hundred mA) you could have a try connecting them as I said before for a test and in order to hear how much power you can get... |
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| DD_Davo |
Thanks, that 50Va 12V one would suit it perfectly, its just i'm not too good with mains voltage.
If i was to purchase 2 wall wart transformers, then should they be regulated or is unregultaed ok, such as
http://www.rapidelectronics.co.uk/r...29506&XPAGENO=1
Finally, if i was to use one of those 50Va transformers (I'd buy from rapid rather than maplins probably) could you tell me how i would wire it up.
http://www.rapidelectronics.co.uk/r...30994&XPAGENO=1
Thats the link for it there, there are 4 pins on the input 4 on the output, so i would presume the middle two pins on the input are birdged and the the outer ones connected to live and neutral
then on the output bridge the middle 2 and connect them to the ground, and the outer ones connect to + and - on the PCB.
Is that right?
Thanks for your time and help |
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| Davide82 |
unregulated is OK.
The 50VA type should be connected depending on the voltage in your country: if you have 240V then primary windings whould be in series; if you have 120V then they must be put in parallel.
The secondaries should go as you said.
Remember to put fuse with the mains wire (a 0,5A fuse).
If you prefer just go with the wall warts, they should be ok... and are already protected. you won't get much power but you can upgrade after... |
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| DD_Davo |
240V so series then, so 4 pins if the outer two are for the live and neutral (+ and -) ill bridge the middle two.
So if i fuse the live wire on the input side, which would be fused by the plug on the end of the cable, but you suggest i use a 5A fuse rather than 13A?
I may stick with unregulated ones then thanks. |
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| Davide82 |
| I mean 0,5 A fuse, not 5A! |
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| DD_Davo |
a 0.5?
I thought that the only fuses that existed were 13A 5A and 3A |
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| Davide82 |
| wrong, there are even 0,1 A! |
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| DD_Davo |
I;m trying to find these fuses in www.rapidelectronics.co.uk
Why would i need such a small fuse though, and also where would i place this fuse, becuase the two wall wart transformers would already be fused.
Thanks |
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| DD_Davo |
ah thank you :) so its the 500ma fuse, quick blow i would guess would be ideal?
So where would i be using this fuse, as the trasnformers will already be fused?
Thanks |
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| Nuuk |
DD, a word of caution! If you don't know where to use the fuses, how will you determine what rating you require?
If you buy a transformer, it wll usually tell you what fuse it requires and that would go on the primary side, ie before the mains switch. :att'n: |
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| DD_Davo |
Well thats the thing, i think i know how to wire one of these up, and is the correct transfomer for the cicruit (50Va)
http://www.rapidelectronics.co.uk/r...30994&XPAGENO=1
But i don't really want to mess around having live wires everywhere. So the circuit requires 2* 12V 2A transformer as shown in the manual here
http://www.rapidelectronics.co.uk/r...30994&XPAGENO=1
But hopefully as davide82 said, if i use two 12V 1A unregulated transformers and wire them up as the manual for my PCB shows for 2 batteries, then it should work i.e. these:
http://www.rapidelectronics.co.uk/r...29506&XPAGENO=1
What do you think?
Many Thanks
(oh forgot, yes so what i was trying to say was, if i purchase the transformers above, the pre wired ones if you know what i mean, the plug in wall ones, i shoudln't need a fuse, since they will already be fused, is that right?)
Thanks |
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| Nuuk |
| I have no experience of using the wallwart PSU's but would presume that they are fused. |
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| pinkmouse |
| Why not just buy a couple of 12v batteries and a charger? Some people actually prefer that setup anyway. ;) |
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| Davide82 |
You need to fuse ONLY IF you use the 50VA tranformer;
if you use the two wall warts, I read they are already protected and have overload cut-off.
For simplicity I suggest you take these two wall warts: you won't get much power but it's simple and reliable. Just plug in.
AND it's always useful to have them laying around because if you plan to make some other electronic projects...
You can always upgrade later. |
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| DD_Davo |
great thanks, ill stick to that then for now, and i just wire them up as shown in the manual for the amp
http://www.velleman.be/Downloads/0/Manual_K4003.pdf
Like two 12V batteries?
I have just looked on rapid for 12V batteries, they sell them but there capacity is low so i doubt they'd last long. Hopefully though if i use 1 12V 1A transformers (totalling 24V 2A) the amp should perform quite well.
Thanks |
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| Davide82 |
Yes wire the wall warts up just like the batteries.
Avoid batteries, you will need other things and money to recharge them.... |
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| DD_Davo |
I'm going to use them transformers, but i've just tried two brand new duracell M3 9V pp3 batteries. Now, i put them on the speakers pop (so theres power going through the amp) but nothing happens. However if i unplug one battery, then wait 5 seconds, connect it again then unplug it again quickly the amp sounds for about a second (and sounds perfectly fine) but it lasts for about a second.
Now I would have thought 2 Alkaline M3 Duracell 9V batteries should indicate the amp to be working (even if its not very loud) but it didn't function very well. SO do you think that the capactiors could be damaged or the IC since the IC supply voltage (18V) was high enough
Thanks |
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| Davide82 |
I think that if you wire up the batteries in the correct way (+, GND, -) as told in the manual it should work.
But the capacitors should be ok, because the only way they can be damaged is reversing polarities (very important) and overvoltage.
The IC could have been damaged but it's too strange it works for a short time!
Further investigation have to be done...
If you have a multimeter you should check the current consumption through the batteries and re-check all the assembly work you've done on the board. |
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| DD_Davo |
well the capactiors should be in the right way, well im 100% certain so they should be fine. I'll take a multimeter to the board tomorrow and see, its annoying me though becuase those baterries were wired up as
- + - +
VB ground Va
which is correct,
If i leave one battery connected and plug in another, the speaker pops, then if i unplug one battery the speakers pop again about 3 seconds later as though current has been discharged from the circuit, so power is gettin through. Also theres the input and output side for audio, if i bridge the input and output pins on the board audio goes from source straight to speakers, so audio is getting through, its just when you turn the amp on it doesn't seem to do anything. Very odd. Can you test capacitors with a multimeter?
Thanks |
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| ROVSING |
| This might not be the best way of testing the capacitor, but you can unsolder the capacitor and then "load" it with a 9v batteri put on your multimeter, if the current is falling slowly something like 0,1v each step the capacitor will be ok. If it "unloads" fast it might not be ok. |
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| DD_Davo |
| thanks ill try that, since it still doesn't work |
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