Building the Tiny Giant amp

[PRR]

> a switching jack

Very difficult. There is a jack which will do it but more expensive than a switch, or just un-plugging the device not in use.

[butch199]

I have put together tiny giant using verified vero board on this forum, but I am at a lose for why it is not working. Here are volts of :
tl072
1=5.84
2=5.82
3=5.95
4=0\511.64
6=11.24
7=11.23
8=11.64
tda7240a
1=5.51
2=5.48
3=5.43
4=0
5=5.49
6=11.64
7=5.54
when I audio probe the signal, there is a signal going to the speaker out plug but not enuf to drive speakers,  the signal will play thru an amp, but to clarify it does not drive speaker cab. When I plug into cab I here total silence. Ideas?
I appreciate any assistance

[butch199]

bump=can any one assist.
Thanks

[garcho]

Vero is notoriously treacherous. Maybe take some pictures of your board and wiring and post them here.

[butch199]

The first TG I built worked great, I have built from the kit 2 addition TG's with no sound, after many hrs of looking for a bad solder connection, wire or ?, I gave up and determined that it must be the IC TL072  or the TDA. So I took the IC and TDA from the non working amps and replaced in my working TG. I determined that both TDA's that came with kit were not working. I get what looks to be correct voltages but the amp are not amplifying the signal. Talor, could you have gotten a bad batch of TDA's? I have order 2 more kits and will let you know the outcome
Thanks for any assistance or ideas.

[Taylor]

I determined that both TDA's that came with kit were not working. I get what looks to be correct voltages but the amp are not amplifying the signal. Talor, could you have gotten a bad batch of TDA's?

Hmm, I will discuss this with forum member Waltk who is the one sourcing the parts/putting the kits together. On one hand, in my own experience of building over 1000 electronic doohickies over the years, I don't think I've ever been able to blame a problem on a bad chip. On the other hand, as parts get harder to find, as is the case with the amp chip here, I suppose it becomes more likely that the few you can get could be dodgy. I haven't heard from any others recently that they had this problem, but if anybody else thinks they might have a bad chip, please chime in. If it turns out that there is a bad batch of parts I'll certainly refund anybody affected.

[waltk]

Hey Butch199.  The TDA chips that Taylor sells with his TG kits are purchased in batches of 100+ (with many successful builds), so I think a "bad batch" is pretty unlikely. 

The TDA7240 has a boatload of on-chip protection built in - however, I've heard of them "going bad", and managed to blow up a couple myself.  Unfortunately, once the chip is blown, there's no recovery.  So it's possible that something about your second and third builds killed the chips, and swapping them into your first (working) build wouldn't tell us when or how they went bad.

Taylor provides exceptional customer service, and I'm sure he'll help you get back on track.  Meanwhile, maybe there's something we can figure out about what happened with these last 2 builds. 

Do you have a way to post a picture here?  A good high-res picture of your build might tell us something.  Also, were there any other differences between your first successful build, and the last 2 that aren't working?  Power supply? Enclosure? Wiring/jacks?  Did you verify that neither the speaker output terminals are grounded?

-Walt

[butch199]

Walt;
I agree, Taylor has been great and I use my successful build to play out. I will take some pics and send them. The voltages all seem normal(as compared to my working amp. When I trace the audio it goes to the speaker out but is not amped. Is there one of the resistors or caps that I should pay particular attention to that could be causing my problem?

[butch199]

Walt and Taylor;
My bad! figured it out, bad volume pot and broken wire haunted me on both builds that were not working.
Thanks for a great project

[Taylor]

Glad you were able to sort it out!

[waltk]

Well done!  So just to wrap this up, were you able to get both of them working after finding the problem?

[butch199]

correct all is working, I actually got some bad 10K pots from china. 5 out of 10(10k audio pots) were bad ,
I appreciate all of your assistance

[kinski]

Hi, could I use this battery to run the Tiny Giant? If so, any idea how many hours I'd get out of it? Not having to plug it in would be great. I'd bypass the regulator.

DC 12V 6800mAh Rechargeable Li-polymer Li-ion Battery:

http://www.ebay.com/itm/DC-12V-6800mAh-Rechargeable-Li-polymer-Li-ion-Battery-w-US-Plug-Power-Adapter-/261808093692?pt=LH_DefaultDomain_0&hash=item3cf4fa79fc

[waltk]

Yep

[PRR]

TG loaded in 4 Ohms, played steady-LOUD non-stop, will drain a 6.8AH battery in around 3 hours.

In more normal playing (some soft passages, breaks, etc), perhaps "all day".

It's not a bad choice.

You maybe can locally find a lawnmower battery of more AH for about the same price, but much heavier and no charger and it will slop acid if mistreated.

[fatecasino]

I intend to build a battery powered tiny giant too.
I am thinking of using a 12V lead acid battery, which means it starts around 14.2 volts.
Now,
1 - if I keep the lm338, what will it happen when the battery goes under 11volts?
2 - if I remove the lm338, will the amp chip manage the 14.2 volts?

[Taylor]

If you only ever want to power it with a battery, I think you're probably better off leaving the regulator out as in the diagram above. The amp chip will have no problem running up to 18v or so.

[Jonsuit]

Hello, I am working on the Tiny Giant, and have a bare minimum of experience with electronics. This is my first attempt to build. I have had a few problems and am working through them as I go.

However, I believe I may have ruined the TDA7240 chip. (I connected power to ground and vice versa on the PCB then plugged it in). I am not as careless as that makes me sound, but no less, I did it.

My trouble is finding a replacement chip. I can't seem to find one through large name distributors, and many I find through eBay and the like are expensive for what it is.

Is there a know alternative? I was looking at LM1875, but don't know what all I might need to consider before determining if this is a suitable alternative.

Thank you for any advice and time.

[PRR]

> 12V lead acid battery.... will the amp chip manage the 14.2 volts?

This IS a Car Sound chip. MADE for "12V" lead battery plus heavy charge/discharge currents. While modern cars rarely hit 14.0V, older cars did. Car regulators fail and put higher voltage. "Load dump" when a heavy inductance (motor or field winding) is cut-off causes short 40V spikes.

Unless your busker-rig has massive chargers, the TDA7240 will be fine right off the battery. (With a fuse, as Jonsuit shows.)
________________

> eBay and the like are expensive for what it is.

Prices I see on eBay run US$2 for one, $15 for ten(!), to $5-$10 higher-price (which may not be better). Considering what is in there, and what it does, $10 is not "expensive" IMO, though I would try the $2 ones because it is not rare and not liable to fakes.

[Jonsuit]

Thanks for your reply, PRR. I adjusted my expectations, and bought 2 for $10 with free shipping. This way I'll have a spare one to blow before finding a new hobby.