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Old 15th September 2010, 12:06 PM   #11
tuneman is offline tuneman  Australia
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removed 101 and 201,

sound remained unchanged.

a side note, to begin with i removed the transistors and checked for the sound and it was gone, then i realized i had removed 102 instead of 201!!, opps my bad
i dont know if this means anything or not,
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Old 15th September 2010, 02:46 PM   #12
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That would seem to indicate that the problem is in the 100 series channel. That channel may have a leaky transistor. With no power applied, you may be able to find the defective component by measuring the resistance between the legs of the individual transistors and comparing them to the readings in the other channel. The components with similar names (Q103, Q203) should be the same in each channel.
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Old 16th September 2010, 12:38 AM   #13
tuneman is offline tuneman  Australia
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ok, i have a bit of a probe around!, see what i come up with

thanks for helping me to, much appreciated!
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Old 16th September 2010, 03:20 AM   #14
tuneman is offline tuneman  Australia
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i did some checking and it seams(according to my measuments anyway!) that theres 3 or 4 of the various trans are measuring differen't, i might just replace the whole lot on that side theres only 10 or so.

i might have to put another post up cause i carnt seem to find the numbers on them in any documents i have,

on another note, i had it setup for testing and i noticed that when the amo is at idle with no input and its just outputting what sounds like hiss or pink noise that channel(right) the one making the noise, isnt as loud a hiss as the left channel, but when playing music theres no difference.
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Old 16th September 2010, 02:40 PM   #15
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Initially, the complaint was that it made a noise after switching it off. Is the hissing a new problem?

Before you begin replacing large numbers of components, there are a few other things you should confirm.

Is pin 12 on the power supply IC immediately going to 0v after you remove remote voltage?

Does the noise/hiss with/without RCAs plugged in? You stated it hissed with no input but that could be with the RCAs plugged in with the signal source volume set to 0.
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Old 16th September 2010, 03:42 PM   #16
tuneman is offline tuneman  Australia
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Join Date: Feb 2004
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the hiss has always been there, to hear the initial problem better i used a 1" titanium horn motor and flare that i had lying around, similar to what i have in my car, because these are quite efficient( 109db) they tend to show up amp hiss and anything else

all my checking was done with no rca's plugged in, i dont have an audio scorce where i was checking the amp, only power, and pulling it in and out of my car is a pain.

i was just switching the driver between l-R channels and it was a noticible difference in horn hiss with the left being quieter, i probably should compare it to a good one, i also bridged it across the 2 channels out of interest and it still made the noise as well.
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Old 16th September 2010, 04:00 PM   #17
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That may not be a good speaker to test this amp. It's ~20dB more efficient than the average speaker. The level of hiss may be perfectly normal for this amp and wouldn't be obvious with a more conventional speaker.

Is pin 12 on the power supply IC immediately going to 0v after you remove remote voltage?
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Old 18th September 2010, 04:01 AM   #18
tuneman is offline tuneman  Australia
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dosen't drop completely 0, it drops to 5-600mv or so according to my meter and slowly reduces from there,

the hiss is normal but i assume it shouldn't be louder in one channel, and by loud i mean i still have to put my ear in the horn mouth to hear it so im not talking massive hiss

Last edited by tuneman; 18th September 2010 at 04:04 AM.
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Old 18th September 2010, 01:12 PM   #19
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If it's drops instantly to less than 1v, that's good enough.


The his is louder on one channel in some amps because additional active components are required to invert one channel (so it can be bridged).

What voltage do you read on the third leg of transistors Q101 and Q201 as remote is applied, after 5 seconds and immediately after the remote voltage is removed?
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Old 19th September 2010, 03:21 AM   #20
tuneman is offline tuneman  Australia
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101 - when remote applied, varies between a couple mV then in 4 seconds goes to 23.5 mV and stays there, drops to 0 in about 10 seconds when remote removed.

201 - when remote applied it does the same except goes to 37.6mV and stays there,
does the same as 101 on turn off as well.
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