car amp help

[jleaman]

can any one help me with a car amp im looking for schematics for a Infinity Kappa 255a Amplifier the amplifier powers up and all 4 front and read channels work but the sub amp channel doenst i dont know if i can power this amp up with out the heat sink on or not. Can any one sujest some thing to me. It doesnt blow fuses at all either.

Help.! me fix it for my friend Thanks.

 

[JOE DIRT®]

Jason...you can power it up without the heat sink for a short period of time....idle current is Low with no load......I would trace back from the outputs and find your problem...if it is not blowing a fuse good chance its something minor....there are fuses inside besides the external fuse


Cheers!!The DIRT®

 

[jleaman]

ill look at at that again. thanks for the tip. i really want to get it going as it is a nice amp for my friends car 50w x 4 a 200watts x 1 5 channel amp.

 

[jleaman]

i cant see any other fuses other than the 2 x 40a ones on the out side.

 

[Diode]

Do you have power on that channel? Check the collectors of the outputs. Trace back from the supply to the outputs to see where the rails should be. Is the low voltage supply, for the pre-amp and drivers shared by all channels? If not, chances are, they use a zener regulator and resistor for +/- 15V. Check for and make sure that it is there too. Check for any bad or questionable solder and resolder it. Gray or dull solder is ALWAYS suspect. Make sure all RCA jacks have good solder and look for broken pins on them. Make sure that any or all gain pots are in good working order. They are a great place to lose signal. Be sure that the filter caps are soldered in good and no broken pins. If you have power on the outputs, your answer is in the preamp part of the circuit. If you have a scope, follow the signal. If you don't have power, do the voltage checks at the PWM and feedback circuit and see if things are working. If you have a scope, check the gates of the power supply for drive waveform. If that isn't there or comes and immediately goes off again, the PWM is in what we powersupply jockys call "burp" mode. This means there is a problem with the circuit such as bad FETs or some diode or the feedback section isn't right. There could be a shorted turn on a filter or transformer, hell, it could be a bunch of different reasons. If it is NOT blowing fuses, chances are it is not either an output or power supply FETs, which is good BUT a "burp" situation isn't really good either, as it may be a pain to find and repair.

I hope these things help lead to something. Without looking at it myself, I really don't know......

Good luck!

Chris

 

[jleaman]

well i did all that the psu is working just fine. i mesured all voltages and it seems fine i could not find any other fuses so yeah. my next step is to put ossiliscope on the out put and start taping around the pre amp section and see if i see any thing. I hope i can get it working. the fets are all ook and every thing tests ok.

 

[JOE DIRT®]

Jason...a thing I built years ago was a signal injector...2 dollar circuit and I still use...it shows you excatly where you have a failure....people might laugh here...but it has saved my butt many times..LOL

Cheers!!The DIRT®

 

[viperguy]

Did you ever found out what was wrong with it? I have the same problem also.

 

[jazzdane]

255a

Jason, Did you ever find the trouble? I've got three of these animals. Jeff.