I ripped the track a little from the edge of the pcb.

I´ll buy more fuses and try this at afternoon.

I using 1,5 A fuse for each rail, fast blow. Its ok?

Thanks for you help.

Hi there:

Had been a long time since my last post.  We survived Puyehue´s eruption, and my new house building, so here i m again.

Now i return to guitar amp construction hobby, cause i still playing with my ruby version, and last week try to play with other guy´s, equiped them with a Roland 30 cube & Gibson SG  8|, other guy with a Traynor 20 and a Squier, and i with my old Faim and Ruby  :grr.  It is like trying to scream at front of Boca Juniors hooligans. I cant ear my self nothing at all.

So now i working in a Gainclone like http://www.generalguitargadgets.com/projects/13-amps/58-lm3886-amp

I mounted a power supply with a 24/24 6A trafo, rectifiers, 2 4700uF electrolitical per rail, so i have +34.9V,0V,-34.9V.
I put a fuse between each rail and V+ and V- of the gainclone, so goes like this:


---Vcc+ --> Fuse----Vcc+(gainclone)

---Vcc- --> Fuse----Vcc-(gainclone)


I switch on, and fuse at Vcc- blows.

I checked disconecting the gainclone, new fuse, at -34.9V ok. No blows.

I checked the pcb and founded a short between Vcc- and Pin11 (pin 11 says datasheet that not conected, anyway, i removed the short). Regard of this, every looks ok.

The tab of LM3886 are insulated from heatshinker with a mika film and a plastic ring in the screw. I measured continuity between the tap and heatshinker, and read something, and quickly goes infinit.

Can you help with some tips?

maybe thats the problem. i dont know how is your circuit, but, as you mentionted, looks like you are making some voltage divisor, so if nothing conected to it, voltage is practically the same as your power supply.

Can you post some draw of your circuit?  Cant figure out wich resistor/cap you are talking about...

Quote
Am I correct in assuming the upper far left connector is ground?

In first page of datasheet, at fifth feature, you can see that it has a "DC OK LED Indicator w/remote indicator contact". I am not 100% sure, but i bet that this"far left connector" is for use to connect for example to a PLC or SCADA system, for "power fail" indication. May be it is a relay output that change of state if power supply shut off. For check it, you can set up you tester for measuring Voltage DC, connect red probe at "far left connector" and black probe at any (-) or ground terminal, at far lower right. You will read something.. don´t know what, but i guess probably something around 5V. Next, without changing the probes setup, unplug of AC your power supply. Keep reading tester display and it should be change to 0V.
If something like that occur, this "far left connector" is NOT GROUND 100% sure.

J M comes first, 

I had asnwer that...

Hi, welcome to the forum.

For kick answer:

If you looking for...

1W:  google for little gem (a circuit with a fet, a LM386, couple of resistor, capacitor, few work, and that´s it.)

around 15 W:  Look for TDA2005 datasheet, bridge circuit. It uses 12V, and work really god. Easy to mount. Few components too.

around 50W:  LM3886 is sure bet. Look in this forum or Gainclone at google.

Hope help.

Dont hesitate to ask.

I found Micron site at http://micronpower.com/products/selection_guide.php

Maybe you can find your model on that table and identify properly how much tension you can expect at terminals.

The picture posted looks like MD120-24-1 model.   Datasheet says that it has an adjustable output of 22-28 V

Here datasheet http://micronpower.com/pdf/MD120-spec.pdf

Hope help.

Maybe you can try the next:

First change the tone pot for a 100K resistor between both 100nf caps, and see what happens with all the other pot at max.

Second part: Change the above resistor by a jumper, and see again what happens with the others at max.

If nothing bad with both test, then the pot is guilty, else look for other place.

Maybe you need to take in count, that in datasheet of LM386, when you short pins 1 and 8, is for max gain of the chip, they suggest you to put a 10uF electrolitic capacitor between this pins. (positive with 8, negative with 1). Perhaps it cause the trouble..? ...Not sure, but one more test that you could try.

By the way.... obvious think first......double check all conections.....specially pot conection, i mean, check where you conected each wire at pot tips.

TDA2005 bridge datasheet circuit !!  :tu: :tu:

Not clear yet about LED function that you want.

If perhaps you want to use it like a "power on" indicator, may i suggest use a resistor of 330 ohms connected in serie (like J M explained above) instead of 2200?

I say it because as rule of design, i think that a tipical LED has a 2V drop of tension, and is necesary flow about 22 mA of current trough it to bright it on. 

So, 9V-2V = 7V -->  by ohms law,  7V/22mA = 0,318 Kohms---  around 300 ohms.--- ¿330 ohms more aprox commercial value?

About power used by LED connected like that...

If we use an 330 ohms resistor, current will 21.2 mA,  so, Power = V*I = 9V * 0.021 mA = 0.19 W

Hope help you

I would look two main characteristics for a speaker (behind of its size, of course).

First:  Bandwidth ( from around 30-50 hz to 5800-6000 hz ).

Second: SPL  (the higher value, the better) SPL is how much sound pressure produces the speaker with 1W of signal, measured at 1 mts of distance. The unit for this are [db] so a difference of 3 db means twice the sound pressure. You actual Alpine speaker push 84 db. If you find the same speaker model but with 87db, it pushes twice.  Figure that with the same ruby you produce a lot more of noise  :trouble

I already mounted an about 15 W amp stage using TDA2005 datasheet circuit (bridge one). It work pretty good too.

Simple, few commons components and it work with 12V.

It is another option that you could choose for use with Projet 27 preamp...

About your speaker, i think that the main bad think it has is it´s  frecuency response (31hz-700hz), because guitar´s frecuencies goes from few hertz til around 6 Khz. Probably your guitar will sound very bass, and without any bright.

I used a satellite speaker from my home theather in a try with Ruby Amp and it sounded really good.

Hi Trent:

Welcome to the board.

May i suggest you to go straight forward to the Ruby amp.

It is ideal for begginers. It is easy, very cheap, the parts are very common, and best of all, if you make every step reasonably well, it work pretty good. It´s only disadvantage is very low power (about 1 W), but is ok for a practice bedroom little amp.

Here the link www.runoffgroove.com/ruby.html

Basicaly this circuit use an LM386 chip, which is an operational amp. Here you got the datasheet of him. LM 386 Datasheet

Ruby has an improvement of the suggested circuit at the datasheet, and use a FET as buffer stage, it really worth it.

By my little experience with this amp, it will sound as good as good be the speaker that you use with him. Maybe you can try several til you get one that you like.

Any question, don´t hesitate to make it.

I see.  Magazine paper seems to be better than any else (..usually existing at home). Ironed around 2 mins at half temperature.

But one more question remains.... there are a lot of kind of magazine paper. To make an example, wich one to use? Say.... similar to newspaper? I mean... some magazines papers (inside pages, of course) looks similar to newspaper.  Other magazines.....let me think one similar for any country.... perhaps playboy centerfold page? (ejem....never see one, a friend of mine told me 8|)

Or wich other your says?

I hope be enough clear...

Hi folks:

I had been making some pcbs, for ruby and for a bluesbraker.  In past, i had been etched other PCB in my secondary school (around 90's) , i.e. for a laboratory power supply, really, no big deal, big traces, no very difficult at all. I used to make it with a couple of indeleble marker´s (a thin and a thick one). Then, it goes to Perchloride ferric bath.

Lately, when i mess around with ss-amp hobby, start using the "print with a laser printer, transfer to the pertinax with an iron and put the pcb in to Perchloride" method.

Its looks easy and better than pencils for difficult designs, but i can´t find the optimun combination between:

- wich paper best to use?: i tried regular bond paper and illustration coated paper, always printer with HP Laser. Bond worked acceptable, but not good enough, cause some track looks slighly corroded. Illustration coated paper didn´t work well with the printer. Looks like toner cant fix properly to the paper and see some "ghost" appear on the sheet.

- I use an iron of 1200W. Wich better? The hottest temperature that it can reach? I´m affraid that if too much hot, take off/detach copper of the pcb. How much temperature? How much time?

Any know a cheap, home made, method better than mine?

Can any name his own method that use? No industrial, of course.

Not sure if it is the right place of the forum to put it post. Please move it if not.