Amp trouble - infinity Kappa 202a

[silversweden]

Just kidding i did find both the datasheet And
the component to buy!

BCX68-10,you forgott the "C" wich made me
confused

it will be a challenge replacing them, any tips
using just standard equipment.

Dont have a hot-air thing. maybe i have to
buy a simple one, or is it possible to make it
without it?

Three legs and just one tip, can be a problem =)

[Perry Babin]

Sorry about the typo. Hopefully you remembered the SMD codebook and found the correct part number quickly.

I've never had a hot air work station and have never had any trouble removing any component from any circuit board.

If you have a good, hot soldering iron, apply enough solder to bridge all 3 legs. Then go to the top and apply solder to the tab. If you quickly go back to the 3 legs and apply heat, the transistor will slide from the pads. The extra solder gives the leads extra thermal mass and prevents them from cooling before you can get back to the other legs. Don't use excessive force. When the solder is hot enough, the transistor will easily move off of the pads.

Clean the pads with desoldering braid and apply solder to one pad. Heat the solder on that pad and set the component in place. Then solder the rest of the leads.

Don't forget to insert the resistor in the b+ line (between the PWM board and the lamp board) before applying power.

[NanoFrog]

Hi.

Try this for hot air soldering.

http://www.makezine.com/blog/archive...t_air_sol.html

[silversweden]

Hi Perry, i replaced the blown transistor on the
lamp board. One of the leds also broke so i
replaced that one as well.

The good thing is that all the leds now lit as they
should. But they are not equally bright.

It looks like this:
(this is the green lights that i replaced with blue leds)

One of the leds are really bright.
The second one is just bright.
And the third is not so bright.
The last is barely visible at all.

I measured and they all have 3,35 volts.

What happens??

[Perry Babin]

It's never a good idea to run LEDs in direct parallel. Unless the LEDs are very closely matched, the brightness from one LED to the next can be significant.

The forward voltage of the LEDs may be different. If you cut the trace feeding one leg of each LED and insert a resistor in series with each LED, the brightness should be close to the same for all of the LEDs. If you have a resistor in series with each LED, you can remove the one in the B+ line (coming from the PWM board).

You'll have to calculate the resistor value from the desired LED current and the B+ voltage.

If you only changed one LED and the rest were in the circuit when the transistor failed, the others may be injured and won't work properly (they will need to be replaced).

[silversweden]

Hi perry i understand what you are telling me.
But its strange because the led thats the brightest
one now after replacing the transistor and the led.
Its in the same place as the led that broke before!
Seemes suspect to me.

Its almost easyer to just make a completly new
led board =)

[jol50]

I have an issue with LEDs in an audiobahn. One does not work, and the power led goes on/off at random but the others work ok. I tested and got 4.9V in the whole circuit. There is a resistor on each led that drops it to roughly 2.8v I think it was. They are all the same, the non working one tests very slightly higher in ohms on its resistor....but if I jump a working one after resistors to it they both don't work. It shows same resistance as others in the led. Maybe I don't know how to test them but still why the power one going on/off at random? I checked a similar amp and found the same 5v for the lights. I thought maybe it had AC in the 5v but my meter freaks out when I try to test that if it is not supposed to. But this amp is not worth that much and I am running out of time on it. The amp does play music fine. I half looked for a shorted cap/resistor in the 5v power area but found nothing.

[silversweden]

hello! it was some time since last but now i am trying to finish what i started. i replaced the leds with real 12v mini bulbs... but now none of them lit - the voltage seemes to be to low, i had one connected first and it lit very weak, now with all of them in place no one will light.

does anyone have a schematic to this beast?

[Perry Babin]

The LEDs had current limiting resistors in series with them. Those would limit the current too much for incandescent lamps.

Email me for the service manual.
babin_perry@yahoo.com