need tda7240 guitar amp schematic

[PRR]

> output:12v 2.1Ah

"Ah" ?? The "h" generally implies "hour". A battery has a discharge time; a wall-supply works forever (no specific hours).

Yes, it could be a typo. The people who write manuals and labels often don't know electricity.

[jogina111]

does wallwarts supply exactly 12 volts? Or it has some excess voltage? The TG schematic shows that its powered by 11.6 volts. Does that makes any difference using 12v?

[Jdansti]

it says ac-dc adaptor/charger input:220v-60Hz 
output:12v 2.1Ah

Does it really say 2.1Ah or just 2.1A?

Thanks for the catch, Paul.

[jogina111]

shop says "its designed for batteries..thats a typo. That charger doesn't discharge."

[PRR]

> The TG schematic shows that its powered by 11.6 volts

Read the chip spec-sheet.

It is made for CARS. Car radio etc.

A car's electrical voltage may be 12.6V full battery engine off, 10V on a weak battery on a cold dark night, 13.6V-14.4V when engine is revved or cruised on a full battery. You expect the radio to play in all these cases.

(A car's voltage can also fall below 10V when cranking a cold engine, or be jump-started with 24V... you don't expect the radio to play right in these cases, but the chip must survive. The TDA series will shut-down at 18V; in shut-down they will survive 40V for a little while.)

It is "legal" to run the TDA7240 with up to 18V supply. However at 18V it can get VERY hot; and if you touch 18.1V for an instant it may shut-down. Taylor decided it did not need to work that hard, or that close to shut-down, with laptop supplies which may range from 16V to 20V. That's why he added-on the voltage regulator chip. It could be tuned for 10V out and be fairly loud, 14.4V to match the factory show-off specs (except 14.4V is too close to the 16V of some laptop supplies). He probably penciled "12V", then when he calculated standard low-cost resistor-values to set the regulator, it came out as 11.6V.

Without the regulator you may run 10V to 16V, although at the higher end of that range with lower-ohm speakers you may run into over-heating. Power output rises with voltage, but 10V to 16V is not a "big WOW!" kind of change.

[Jdansti]

does wallwarts supply exactly 12 volts? Or it has some excess voltage?

Along with what Paul said, we don't know at this time whether your wallwart is regulated or unregulated. Most inexpensive models are unregulated, which means that the voltage without a load could be the stated voltage or even a little higher. This will change once you apply a load. Depending on the current draw of the load, the voltage could drop below the stated voltage.

The purpose of the 338 regulator on the TG is to make sure a laptop PSU, which could put out as much as 20V, doesn't damage the TDA amp (or cause it to shut down due to heat). If I understand Paul correctly, the TG will not be in danger of overvoltage from your PSU rated at 12V, even without the 338 regulator.  If it were me, I would bypass the 338 regulator if I were using a 12V PSU. One reason for doing this is that the PSU might not be able to deliver 12V to the input of the 338 regulator. If we assume that the PSU output drops to about 10V when powering the TG, you're going to lose as much as a couple more volts due to the operation of the 338 regulator. Now you've only got around 8V to power your TDA, which would not be optimal.

Please help me out, Paul, if I've misstated anything.

[jogina111]

oh! I'm going to my granma next week and Im gonna get a laptop psu.. She got an old one that she isnt using anymore!

[Jdansti]

Good news!  Grandma to the rescue!  You'll be set once the parts come in. 

[jogina111]

The laptop psu was damaged. I brought it to the best repairman I know but it cant be done... I dont know why...so Im stucked with a 12v 3A wallwart...which components should I ommit or what should I add?

[Jdansti]

The laptop psu was damaged. I brought it to the best repairman I know but it cant be done... I dont know why...so Im stucked with a 12v 3A wallwart...which components should I ommit or what should I add?

I'll look at it shortly and let you know what changes you'll need. Did the package arrive yet, or are you just preparing?

[Jdansti]

Here's what you'll need to do.

-Omit the LM338T.
-Install a wire jumper between the LM338T Vin and Vout pads as shown. Do not connect anything to the third ADJ pad.
-Omit the regulator's 1k resistor.
-Omit the regulator's 120R resistor.
-Supply +12VDC to the + pad.

[jogina111]

thanks! Im just preparing the power supply and the enclosure... Theres no mails today because its weekend..

[Jdansti]

If you get a notice to go to the post office to pick up your package, you should not have to pay taxes on it. Tell them it is a gift (which it is) from someone you know in the USA who has the same hobby as you do. Be persistent!  I've read horror stories about people being cheated by corrupt postal workers in the Philippines.

[Jdansti]

I hate the postal system!

I've been tracking the package with the TG kit and a bunch of other parts that I thought you could use to build other pedals. Your package was clearly addressed to your address in the Philippines on the Express Mail form, the Customs form, and on the package itself. Somehow, it was sent to Poland and it is sitting in a post office there waiting for you to pick it up. Grrrrr!!!

I spoke with a person today that handles international shipping problems at the US Postal Service, and they have started an investigation. They are going to ask the Polish postal service to forward the package to the Philippines.  It is possible that it could be sent back to the USPS, who would then try again to ship it to you.

Sorry for the extended delay. I'll stay on top of the investigation and keep you updated. 

[jogina111]

thanks John. Thats quite disappointing.  I  thought its on the way to the philippines. I hope it wouldnt get stucked to other places where it would stop over..

[Jdansti]

Yeah, it wasn't even supposed to go through Poland. Some one in Chicago must have thrown it in the wrong bin. The Philippines and Poland bins are probably right next to each other. It should have been routed east through California, not west. I'll stay on top of it.

[jogina111]

no need. I've just recieved the package.... I'll open it later. Thanks a lot John...

[Jdansti]

What???  Either it's been in the Philippines for over a week, or someone in Poland forwarded it to you. Glad you got it!  Hope you didn't have to pay anything to receive it.

[jogina111]

actually, I did... 40 pesos or 0.90$..

[jogina111]

actually, I did... 40 pesos or 0.90$..