Sansui AU-G11X Amp - Help

Gandalph · 2nd March 2006, 01:20 PM

Greetings from Norfolk

Can anybody help please, I have this Sansui Amplifier which I use for a dance class, BUT it has a speaker protection circuit which seems to be either

(a) not working properly or
(b) the amplifier output is out of limits for some time.

The effect is that when switched on the output protection circuit operates to protect the speaker and remains in the 'protect' state for a long period (many minutes) Once it has operated (i.e. to output signal to speaker) then if switched off and then on after a short period the delay is much shorter.

I suspect either a leaky capacitor, or an out of adjustment on the dc level of the output. Can anybody advise with data to enable me to rectify.
I have traced out most of the protection circuitry, but parts are not sensibly accessible, even to determine values.

Richard

Netlist · 2nd March 2006, 01:39 PM

Monitor the DC status before the relay. If that is fine, suspect the protection circuit. Look for capacitors, sometimes bipolars are used in that area.
If sufficient DC is present, change some caps in the signal path.
Measure and suspect the diff pair. A schematic would be handy in this particular case.

/Hugo

Gandalph · 2nd March 2006, 02:53 PM

Greetings from Norfolk

Having looked into the circuit to the extent that I have identified the area of the circuit, it is either the protection circuit timing (a 47 uF charged via 180 K from 3 V, 'clearing' the protection circuit when charged to 1.36 V. The rate of charging also appears to be controlled by some other factor than the resistor (180 K). dc monitoring of the amp output signals is also probably a factor - there is an 'integrated / thick film circuit' which takes these signals in, as well as others and appears to be involved in the protection.

Richard

anatech · 2nd March 2006, 03:00 PM

Hi Richard,
The IC is probably a SIP, TA7317P. It has AC detect too, if they are using it. This IC is seldom defective.

Look for a single diode charging a 1uF (normally) cap. If you look at the waveform with a 'scope, it should be DC with a 60Hz sawtooth on it. They go open so the DC component is reduced as the capacitance goes down.

Other problems have been detailed by Hugh.

-Chris

fonon · 14th October 2007, 07:59 PM

Hi,
My new – old AU-G11X needs to be repaired. I have a problem with the top plate. How to remove it? There are only two screws at rear panel (cover). The both sides aren't connected with the case. The top plate seems to be connected with plastic front panel in the central part. Can You help me?
Regards,
fonon

Netlist · 14th October 2007, 08:29 PM

In 'cases' like this, I take out every screw I can find, till the whole lot falls appart. No kidding.

/Hugo

anatech · 15th October 2007, 12:52 AM

Hi Fonon,
If it has wooden side panels, the other screws are under there. Some have a top panel that will slide back if you undo those two screws.

Hey Hugo,

Quote:

In 'cases' like this, I take out every screw I can find, till the whole lot falls appart.

Ever do that and hear a heavy thump inside? Followed by the sound of little pieces rolling around?

-Chris

fonon · 15th October 2007, 06:36 AM

Hi,
it's not the Sansui's golden age case. The side panels and the front are plastic. The top plate, the bottom plate and rear panel are metal. Look at the attached picture.
Regards
fonon

Netlist · 15th October 2007, 06:38 AM

I noticed you got some nice replies at Audiokarma.
Did you try what was suggested there and also in this forum?

/Hugo

fonon · 15th October 2007, 11:09 AM

Only one post... I don't know still how to do it.

2nd March 2006, 01:20 PM	#1
Gandalph diyAudio Member Join Date: Dec 2005 Location: Norfolk	Sansui AU-G11X Amp - Help Greetings from Norfolk Can anybody help please, I have this Sansui Amplifier which I use for a dance class, BUT it has a speaker protection circuit which seems to be either (a) not working properly or (b) the amplifier output is out of limits for some time. The effect is that when switched on the output protection circuit operates to protect the speaker and remains in the 'protect' state for a long period (many minutes) Once it has operated (i.e. to output signal to speaker) then if switched off and then on after a short period the delay is much shorter. I suspect either a leaky capacitor, or an out of adjustment on the dc level of the output. Can anybody advise with data to enable me to rectify. I have traced out most of the protection circuitry, but parts are not sensibly accessible, even to determine values. Richard

14th October 2007, 07:59 PM	#5
fonon diyAudio Member Join Date: Mar 2007	Sansui Au-G11X - problem with the case Hi, My new – old AU-G11X needs to be repaired. I have a problem with the top plate. How to remove it? There are only two screws at rear panel (cover). The both sides aren't connected with the case. The top plate seems to be connected with plastic front panel in the central part. Can You help me? Regards, fonon

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2nd March 2006, 01:39 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Monitor the DC status before the relay. If that is fine, suspect the protection circuit. Look for capacitors, sometimes bipolars are used in that area. If sufficient DC is present, change some caps in the signal path. Measure and suspect the diff pair. A schematic would be handy in this particular case. /Hugo

2nd March 2006, 02:53 PM	#3
Gandalph diyAudio Member Join Date: Dec 2005 Location: Norfolk	Greetings from Norfolk Having looked into the circuit to the extent that I have identified the area of the circuit, it is either the protection circuit timing (a 47 uF charged via 180 K from 3 V, 'clearing' the protection circuit when charged to 1.36 V. The rate of charging also appears to be controlled by some other factor than the resistor (180 K). dc monitoring of the amp output signals is also probably a factor - there is an 'integrated / thick film circuit' which takes these signals in, as well as others and appears to be involved in the protection. Richard

2nd March 2006, 03:00 PM	#4
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Richard, The IC is probably a SIP, TA7317P. It has AC detect too, if they are using it. This IC is seldom defective. Look for a single diode charging a 1uF (normally) cap. If you look at the waveform with a 'scope, it should be DC with a 60Hz sawtooth on it. They go open so the DC component is reduced as the capacitance goes down. Other problems have been detailed by Hugh. -Chris

14th October 2007, 08:29 PM	#6
Netlist diyAudio Moderator Join Date: Jan 2003	In 'cases' like this, I take out every screw I can find, till the whole lot falls appart. No kidding. /Hugo

15th October 2007, 06:38 AM	#9
Netlist diyAudio Moderator Join Date: Jan 2003	I noticed you got some nice replies at Audiokarma. Did you try what was suggested there and also in this forum? /Hugo

15th October 2007, 11:09 AM	#10
fonon diyAudio Member Join Date: Mar 2007	Only one post... I don't know still how to do it.

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