The GM Voice

fonik · Posted: Sat Jul 05, 2008 8:05 am Post subject:

i tried the new LM7805 regulators on the breadboarded circuit. same effect: the regulator immediately gets hot as does the protecting 22R resistor i use on the positive 12V power rail. the voltage on the +12V rail drops to about 8V.
as soon as i use a stand alone PSU for the 5V everythings going well. i am still puzzled.
where does the heat come from? why does the protecting 22R resistor get hot? could the +/-12V PSU be the cause? i believe not. i tried two different: the power one from my modular and my small switching PSU from my working bench (never have had any problems with both). what would happen if they could not provide enough current?
Question

absolutely clueless.
should i replace the ICs one by one?

blue hell · Posted: Sat Jul 05, 2008 8:36 am Post subject:

Matthias this is nuts ... Shocked

could you draw it as a schematic?

fonik · Posted: Sat Jul 05, 2008 9:41 am Post subject:

jan, thank you so much for taking care. i will surely provide you with a schematic tomorrow.
actually i used thomas circuitry without the PSU. i wanted to derive the 5V from the 12V rail (as done before) by using a LM7805. on the current breadboard i bypass the input with a 100uF to GND and the output with a 100n cap to GND.

blue hell · Posted: Sat Jul 05, 2008 10:18 am Post subject:

You know of course that those regulators can't all be defective, so there must b e some thinking error somewhere, or an unexpected connection, something like that ... or maybe a HF oscillation involved pulling you a leg. Do you have a scope?

fonik · Posted: Sun Jul 06, 2008 3:54 am Post subject:

hello jan, thank you so much for taking care.
i do have a digital scope. unfortunately my workbench is far from my desktop pc since our move to the new house. i will install the scope software on an old laptop today.
i will draw a schematic of my breadboarded circuit, too.

what i really don't get, and i have no idea about this: with no db50xg installed everything works fine even with the 5V regulators. as soon as i connect one of my three db50xg boards the 7805 regulator and the protecting 22R get hot and the 12V rail drops to about 8V (the circuit actually works at this stage, i can use it for a few minutes before it gets too hot).
OTH with the db50xg installed everything is working fine as long as i use an separate PSU for the 5V.
these observations apply to the PCB i etched and to the circuit on the breadboard as well.
so the circuit is actually working, the db50xg boards and regulators are okay.

so give me just a day or two to draw a sketch of the schematic/setup and to install the scopes software (hope it works on this old pentium II 300 machine).

fonik · Posted: Sun Jul 06, 2008 5:29 am Post subject:

this is not my day!?

tried to install the scope on my old laptop using the parallel port. i used the same parameters for base address and interrupt, plug and play and such as on my desktop. i took care not to use an IRQ allready in use. the software does not recognize the scope! as soon as i plug it into my desktop it works! my new toshiba laptop does not have a parallel port anymore! Laughing

what is going on here? i shall not have a Gmvoice? i shall not have an oszilloscope at my workbench (but two floors above)?

sigh...

i stop for now and take a walk in the woods. my wife will appreciate it.

blue hell · Posted: Sun Jul 06, 2008 7:30 am Post subject:

fonik · Posted: Thu Jul 10, 2008 8:19 am Post subject:

hello jan,

still no oscilloscope working, but here are the two schematics.

1st the schematic as i breadboarded the GMvoice.
2nd the schematic according to the board i etched.

since it is actually working it has something to do with the PSU, i think. again, the 22R protecting resistor R100 and the regulator are getting really hot. i have to shut the circuit down in order to prevent them from smoking...

any ideas?

i hopefully i will build a wallwart based PSU (ray wilsons design) soon and try that one.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

blue hell · Posted: Thu Jul 10, 2008 2:00 pm Post subject:

From one of your earlier posts :

fonik · Posted: Fri Jul 11, 2008 4:01 am Post subject:

removed the 22R and got rid of the voltage drop! great. again you saved my day, jan.

simply maths. unfortunately this is exactly what i am missing Shocked

however i am now in need for a appropriate heatsink.
P = V * A, am i right?

how do i calculate the Watt dissipating at LM7805 when sucking 150mA from 15V? Watt = (15V-5V) * 0.150A = 1.5W ?

this question may be silly, but i don't know much about these things. the maths of electronics is still a kind of holy grail for me...

blue hell · Posted: Fri Jul 11, 2008 4:24 am Post subject:

Good, glad it works now Cool

And your calculations are correct.

RF · Posted: Fri Jul 11, 2008 4:38 am Post subject:

Good call, Jan Smile

fonik · Posted: Fri Jul 11, 2008 8:39 am Post subject:

thank you very much, jan.
i had never thought a 22R resistor could cause such problems. i will have to learn more about the maths and general rules and definitions. that's clear to me but i still fear it...

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus

Hey folks, I swear I had an account here but maybe it disappeared. Anyways - I really want to build one of these, and am having a bit of trouble finding an appropriate daughter board. Aside from this:

link

I haven't been able to find any daughter boards, or even a sound card with one attached. Based on the descriptions from the wiki article:

http://en.wikipedia.org/wiki/Sound_blaster

I tried to narrow down the sound cards I'm searching for, just to the ones with the wave blaster connector:

link

Still nothing though (I looked at all the pictures for daughter boards and didn't see one). Any other tips? Ideally I'd like to get a couple because I want to try to mess with them a bit to get some stranger sounds, and may fry it. I know that I might be missing some with the quotes, but I wanted to do a description search in case they just called it a sound blaster in the title. Any tips? Is there a list somewhere of which sound card model #'s have the connector? Anywhere I can buy the daughter boards online for a fixed price (hopefully less than $40 ea shipped)?

Thanks!

-Colin

blue hell · Posted: Mon Jul 14, 2008 7:07 pm Post subject:

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus

blue hell · Posted: Mon Jul 14, 2008 7:27 pm Post subject:

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus

Dan Lavin · Posted: Mon Jul 14, 2008 7:55 pm Post subject:

Colin:

There's a guy in Shagnhai selling Yamaha db50XG daughterboards for US$25 each + US$15 for postage to the USA. I'm assuming you are in Columbus Ohio and not a Columbus in Latin America. HIs name is double-fish1981 for something simliar. Do an ebay search for db50XG under sound cards and he should pop up. A number of folks in the USA and Europe have gotten cards from him, so he seems dependable.

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus

Jackpot!

https://vsr.informatik.tu-chemnitz.de/twiki/bin/view/Sonstiges/WaveTableSoundCards

-Colin

expanoncolin · Joined: Jul 14, 2008 Posts: 17 Location: Columbus