Amp crackles and dies

[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

 

[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.

 

[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...&CTL_CAT_CODE=&STK_PROD_CODE=M30994&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...&CTL_CAT_CODE=&STK_PROD_CODE=M30994&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...CAT_CODE=30351&STK_PROD_CODE=M29506&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

 

[Nuuk]

I have no experience of using the wallwart PSU's but would presume that they are fused.

 

[pinkmouse]

Why not just buy a couple of 12v batteries and a charger? Some people actually prefer that setup anyway.

 

[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.

 

[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

 

[Davide82]

Yes wire the wall warts up just like the batteries.

Avoid batteries, you will need other things and money to recharge them....

 

[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

 

[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.

 

[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

 

[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.

 

[DD_Davo]

thanks ill try that, since it still doesn't work