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Genesis FOUR CHANNEL
Genesis FOUR CHANNEL
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Old 16th April 2019, 02:28 PM   #1
pippolonia is offline pippolonia  Italy
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Join Date: Sep 2014
Location: Italy
Default Genesis FOUR CHANNEL

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
Attached Images
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File Type: jpg modulo.jpg (140.0 KB, 105 views)
File Type: jpg alimentatore.jpg (181.6 KB, 104 views)
File Type: jpg ingressi.jpg (753.6 KB, 97 views)
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Old 16th April 2019, 04:11 PM   #2
jkrokenberger is offline jkrokenberger  United States
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Location: Central NY, USA
The inverting is for bridging I believe. Did you measure the rail voltages to audio ground or power ground? That could explain the offset.
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Old 16th April 2019, 04:35 PM   #3
pippolonia is offline pippolonia  Italy
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Join Date: Sep 2014
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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
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Old 17th April 2019, 01:06 PM   #4
Lenin89 is offline Lenin89
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Join Date: Mar 2019
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.
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Old 20th April 2019, 07:48 PM   #5
pippolonia is offline pippolonia  Italy
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Join Date: Sep 2014
Location: Italy
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
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Old 22nd April 2019, 08:15 AM   #6
Lenin89 is offline Lenin89
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Join Date: Mar 2019
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 !
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Old 23rd April 2019, 07:29 AM   #7
pippolonia is offline pippolonia  Italy
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Join Date: Sep 2014
Location: Italy
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
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Old 30th April 2019, 06:11 PM   #8
pippolonia is offline pippolonia  Italy
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Join Date: Sep 2014
Location: Italy
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
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