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Old 19th November 2005, 12:48 AM   #1
anatech is offline anatech  Canada
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Default Pioneer GM-X304

Hi,
I have a Pioneer GM-X304 in for service. The RCA ground is open to the amp ground. There is a 10V DC offset between the RCA inputs and everything else.

I'm guessing a resistor is open, unless they are using a referenced active ground.

Any ideas?

-Chris
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Old 19th November 2005, 02:08 AM   #2
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Most of the pioneer amps that I've seen in recent years use an active ground input.

What about failure of the negative 15v regulator?
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Old 19th November 2005, 02:14 AM   #3
anatech is offline anatech  Canada
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Hi Perry,
I am not familiar with the new Pioneers for sure, but what you say makes some sense. I'll test the regulator tomorrow AM.

If it helps, all speaker outputs are within mV of common ground. The previous tech (unknown) has replaced all the op amps, looks like twice.
The amplifier does not go into protection either.

Are the inputs referenced to ground via the car chassis? Right now there are left floating on the bench.

Thanks very much for the reply.

-Chris
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Old 19th November 2005, 07:11 PM   #4
anatech is offline anatech  Canada
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Hi Perry,
After some testing I have determined the following.

Both 15V regulators are running fine, but getting warm. The main supplies are + / - 25VDC.

The op amps on the input are not getting any supply power. The entire mess is sitting around 10 above ground.

-Chris
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Old 19th November 2005, 08:07 PM   #5
anatech is offline anatech  Canada
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Hi Perry,
A question. Found an open connection on C873. Unit works if I ground the RCA connectors as this is where the ground ref. is for the input stage. I don't like this approach.

Am I wrong, or is this the way it works?

-Chris
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Old 19th November 2005, 10:27 PM   #6
dce is offline dce  United States
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Default gmx304

anatech,

Did u check if there is a coil in the rca ground line...usually a green
one and very small... if there is check to see if they are open.
some pioneer amps the rca is not directly connected to chasis ground, it gets the ground fron the head unit, the rca ground on some models pass through a coil and goes to the one input of the opamp....can u take a picture of the heatsink and the inside
of the unit, maybe i have a service manual with similar model that we can compare. Ive got some late 90's service manual here.
I wish I can help you more.

dce
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Old 19th November 2005, 11:40 PM   #7
anatech is offline anatech  Canada
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Hi dce,
Thanks, I will try to send them to you tomorrow. PM me with your email address as the pic will be too large to post.

-Chris
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Old 20th November 2005, 04:13 AM   #8
dce is offline dce  United States
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Default pioneer amp

anatech,

email me here at:

cld2080@yahoo.com

regards,
dce
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Old 20th November 2005, 03:55 PM   #9
anatech is offline anatech  Canada
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Hi dce,
You have mail. Many thanks.

-Chris
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Old 20th November 2005, 04:53 PM   #10
dce is offline dce  United States
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Default gmx304

anatech,

thanks
I got the pictures, to me, the inside is look like gmx922 or 1022.
I am looking right now on my files.
It would be nice if you can take a picture of the top cover(heatsink) so I can find it easily on my files.
usaually if they have the same heatsink they are under the same series. thanks

dce

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