Author Topic: need tda7240 guitar amp schematic  (Read 22452 times)

jogina111

Re: need tda7240 guitar amp schematic
« Reply #40 on: September 21, 2012, 12:23:31 PM »
yeah, Im still looking for a psu...so far, 800mA is the highes I can find...

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #41 on: September 21, 2012, 02:08:42 PM »
BTW- There is another option if you can find an AC to AC wall adapter that has 12-35VAC out and is rated at 2A or more. With a few diodes and capacitors, we can easily get you fixed up with the DC power you need.  You'd need to put the extra components on a separate small board. It'd be a good learning experience about power supplies too.
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #42 on: September 21, 2012, 10:19:45 PM »
maybe I could... I need to earn some money first so I could buy a bare transformer. I already got one here but its a 9 volt transformer..
« Last Edit: September 21, 2012, 10:31:45 PM by jogina111 »

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #43 on: September 21, 2012, 11:32:13 PM »
maybe I could... I need to earn some money first so I could buy a bare transformer. I already got one here but its a 9 volt transformer..

Or scavenge one from an old radio or something. Just be careful of the capacitors when you're cannibalizing. They can hold a charge for a long time after they were last powered up.

The reason I mentioned an AC to AC wall adapter is that you won't have to get near the mains power. You could build a plug-in power supply from the ground up, but you better know what you're doing to keep things safe!
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #44 on: September 21, 2012, 11:41:02 PM »
oh! I found one it says:
HT 4098
2A/28VDC
1A/220VAC
COIL:12VDC
Could it be that this is a dc to ac transformer? And I dont even know which poles should go to the mains...

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #45 on: September 22, 2012, 03:43:02 AM »
The "mains" refers to the voltage at the wall plugs in your country. I understand that you have 220VAC or 230VAC at 60HZ there in the Philippines.

The adapter you found takes 220VAC from the wall and puts out 12VDC (I think).  I'm a little confused by the specs showing two different DC outputs, but only one AC input. Do you have a URL that you could post so I could look at it?
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #46 on: September 22, 2012, 09:17:22 AM »
you mean a picture? I'll try to upload it tomorrow...

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #47 on: September 22, 2012, 03:04:47 PM »
you mean a picture? I'll try to upload it tomorrow...

I was hoping to get a URL (web address) for the item and look at a data sheet.  I searched for HT 4098 and couldn't find anything.

I guess that you're looking at a model at a store. If you could get a photo of the specs on the package, insert sheet, or the unit, that might work. The more detailed, the better.  The manufacturer's name would help too.
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #48 on: September 22, 2012, 08:21:19 PM »
oh..i just found it..Not at a store. Its just a scrap.

jogina111

Re: need tda7240 guitar amp schematic
« Reply #49 on: September 23, 2012, 09:53:13 PM »
maybe a transformer from cfl's will do, since a cfl can deliver 18 to 23 watts?

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #50 on: September 23, 2012, 11:56:32 PM »
I don't think so. Too small.

I=P/V

I=23W/220V

I=0.1A  or 100mA

Nice try. :)
R.G. Keene: EXPECT there to be errors, and defeat them...

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #51 on: September 24, 2012, 12:21:09 AM »
Actually, I may be wrong in my last post. If we assume that the secondary is 12V (I have no idea what it really is), then it might handle close to 2A.

I'm just not able to intelligently help you with the CFl transformer idea given that I don't have the actual specs of the transformer in the CFl.  I'm not going to guess due to the danger of being wrong and getting someone hurt or burning your home down!  Maybe someone else knows.
R.G. Keene: EXPECT there to be errors, and defeat them...

PRR

Re: need tda7240 guitar amp schematic
« Reply #52 on: September 24, 2012, 12:40:00 AM »
Compact Fluorescent Lamps do not have anything like a conventional transformer.

I'm real nervous about *any* line-power work by an electrical novice. A mistake on a signal jack gives bad/no sound. A mistake in wall-wiring burns the house down, or stops your heart.

What about a car battery charger? 12V 2 Ampere is a common car-batt charger, is isolated, is polarity-marked. Car-batts do not need filtering, audio does, so you hang a 3,300 uFd 25V capacitor on the "12V DC" output and get around 16V DC no-load.
  • SUPPORTER

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #53 on: September 24, 2012, 01:08:52 AM »
Great idea Paul!
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #54 on: September 24, 2012, 03:06:23 AM »
Okay! I got one! 12volts, 2.1 Amp wallwart... I just hope its not noisy..

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #55 on: September 24, 2012, 10:26:32 AM »
Good news!  We can do things about noise. Is the output 12VAC or 12VDC?
R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #56 on: September 24, 2012, 10:45:22 AM »
it says ac-dc adaptor/charger input:220v-60Hz 
output:12v 2.1Ah

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #57 on: September 24, 2012, 11:46:25 AM »
Are there any symbols next to output labeling such as

______
----------      or       ~




R.G. Keene: EXPECT there to be errors, and defeat them...

jogina111

Re: need tda7240 guitar amp schematic
« Reply #58 on: September 24, 2012, 12:21:18 PM »
yes the--- under ____ is between 12v and 2.1A
and its 220v~60Hz..

Jdansti

Re: need tda7240 guitar amp schematic
« Reply #59 on: September 24, 2012, 12:43:37 PM »
Good, that's 12VDC. So now we just need to decide whether you keep the LM338T voltage regulator in the circuit or just use the raw 12V from the power supply. If you use the regulator, the circuit will have around 10V at the regulator output, which will reduce the amp's output volume.  I like Paul's suggestion of leaving it out.
R.G. Keene: EXPECT there to be errors, and defeat them...