Genesis FOUR CHANNEL

[pippolonia]

Good afternoon,

your help about a Genesis four channel amplifier ... may I say: "half working".

It came into my desk with one channel in short circuit (two darlingtons blow and 47 ohm SMD resistance on a preamp stage broke); after replacements the amplifier works only on right channels.

Main voltages: + and - 18 are ok; +31 on positive rail, -28 on negative rail: is this little difference right ?

Another question: why signal of R channels is present into INV pin of the preamp stage (and these channels play good music), but into L channels pin INV is not connected ?

Sorry but without a schematics it is difficult to understand input stage and, mostly, the crossover circuits and the subwoofer module !!!

Thank for your help. Some pictures of the circuit are attached

Giovanni

 

[jkrokenberger]

The inverting is for bridging I believe. Did you measure the rail voltages to audio ground or power ground? That could explain the offset.

 

[pippolonia]

Hi jkrokenberger,

thanks for your reply.
I measured rail voltages at caps terminals and I noticed a difference (litte, of course) beetween + and -.

Boh, probably it's normal, but tomorrow I'll make some tests changing ground reference.

For the input into preamp module, probably you're right: for bridging purpose, R signal is inverted and L signal are in fase.

So if i don't have any signal into L modules into normal input, the problem are into input stage and / or crossover

 

[Lenin89]

Check the OP amps one by one, check for the Vcc and Gnd are OKAY. Then look what's going on - on every pin for each OP amp - input (inverted and non-inverted) and the output.

Clean up the potentiometers and the switches...sometimes they do some weird stuff.

 

[pippolonia]

Hi Lenin,

after measures you've suggest, i've changed all OP amps (the originals were TL074CN, but I've TL084IN only) and now signal arrives at the output stages; potentiometers and switches are OK.

I don't understand yet because there is a difference between both positive rails (+30 V) versus both negative rails (-27 V): investigations in progress

Do you know nominal idle current of this amp ? Without any TIP in place it consumes 0,8 A

Thanks and happy easter from Italy


Giovanni

 

[Lenin89]

According to my knowledge idle current seems OK.
I had many amps with 2-3volts of rail voltage differences and they all worked just fine, but I can't say if that is your case too.

Happy holidays to You !

 

[pippolonia]

Thanks Lenin. Probably this is one of amps with 2-3 V of difference beetween rails voltage, because there ins't nothing wrong in the circuit to explain this.

And and idle current of 2,0 - 2,5 A with all darlingtons in place are ok for you too ?



Giovanni

 

[pippolonia]

Hi guys,

I made some other tests because 2 - 2,5 A is too much for this amplifier.

Mi problem is my "sound source": an old Ipod with battery carger always connected because battery is broken.

Probably a short circuit between supply ground (connected trought a DC/DC converter to my Ipod) and audio signal ground is the cause of this high idle current (with another audio source, Genesis take 0,8 A only).

And sound is much better

Thank everybody.

Giovanni