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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 16th Jan 2021, 10:46 pm   #1
quiberon
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Default Sansui AU-G11X Broken Speaker negative connector

Hi,

The plastic section that locks the speaker negative wire in place has broken away from the threaded metal centre, this means I can no longer attach the wire.

I'm considering attaching the wire to the other channel negative speaker connection, but...

...The user manual that came with the amplifier states;

"Since the output stage of this unit is in the form of a bridge, the speakers negative terminals (-) must no be connected in common; they also must not be connected to the GND terminal (chassis) of other components".

But I have the service manual and schematic and it would appear otherwise, as it shows the speaker negative terminals are actually connected together and to ground. Also I have done a multi-meter continuity check which also appears to confirm this.

Can anyone else verify this.

Other than occasionally having to servisol the selector switches it has had no problems.
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Old 17th Jan 2021, 10:03 am   #2
vidjoman
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Default Re: Sansui AU-G11X Broken Speaker negative connector

Look at the back of the terminals to see if they are wired directly across. A meter may give false readings if there are protection relays that short the outputs when switched off.
Those look like common terminals and can be easily obtained. Even if you only use the plastic nut.
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Old 17th Jan 2021, 11:17 am   #3
ms660
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Default Re: Sansui AU-G11X Broken Speaker negative connector

The loudspeaker terminal board appears to show separate ground feeds in the manual.

Lawrence.
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Old 18th Jan 2021, 3:19 am   #4
quiberon
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Default Re: Sansui AU-G11X Broken Speaker negative connector

Hi vidjoman,

These are the loudspeaker connectors, the plastic is moulded around the threaded metal shaft and can't be replaced on it's own. Basically the nut part is in the base of the connector and it is the captive threaded part that moves in and out.

Click image for larger version

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What I am going try to do is attach the speaker cable to a solder tag, I think there is enough of a form of head on the threaded shaft to secure it firmly enough.

Click image for larger version

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According to the schematic the protection relay only opens and closes the speaker connections, it doesn't short them. Also the headphone socket still has an audio output when the speakers are in operation, but at much lower level.

The negative connections are all common-ed to chassis.
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Last edited by quiberon; 18th Jan 2021 at 3:33 am.
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Old 18th Jan 2021, 10:36 am   #5
snowman_al
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Default Re: Sansui AU-G11X Broken Speaker negative connector

Can you not use 4mm / Banana 'speaker' pugs?
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Old 18th Jan 2021, 10:41 am   #6
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Default Re: Sansui AU-G11X Broken Speaker negative connector

I'd just replace the connector post. All sorts of similar types are available, but you might not get an exact match, so just swap all four.

Broken ones on power supplies are quite common and I've swapped a good few.

In order to allow larger cross-section wire to be clamped, the wire holes have been made larger over the years and that's left damn all metal supporting the outer parts. If you crank the terminals up tight, they can break, if you plug in heavy cables, any sideways load breaks the posts.

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Old 20th Jan 2021, 12:26 am   #7
quiberon
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Default Re: Sansui AU-G11X Broken Speaker negative connector

They are not sockets, there is no electrical connection within the plastic grip.

I've managed to use a crimp terminal to secure the speaker lead to the connector as in the pic, there is just enough of a head on the threaded shaft to hold it in place.
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Old 20th Jan 2021, 4:11 am   #8
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Default Re: Sansui AU-G11X Broken Speaker negative connector

Those are complete terminal/socket units. The bit of metal you've crimped onto goes right through the panel and it's all held together with nuts on the inside.

The plastic insulation between your crimp and the panel and a matching one on the inside comes with the post/socket unit.

You just undo the nuts inside and take the whole thing out. Most parts suppliers have a range of these things, pick a matching one and assemble it into the panel, reconnect inside and you have a proper job.

You might not get a perfect cosmetic match, but if you change all three the no-one will notice.

Intermittent speaker connections (either polarity) are a very common way of burning out transistor power amplifiers.

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Old 20th Jan 2021, 4:48 am   #9
quiberon
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Default Re: Sansui AU-G11X Broken Speaker negative connector

The connectors aren't actually mounted directly on the rear panel, they are on a sub-panel which is held in place by the screw in centre of the four connectors.

The F-4821 PCB is then soldered onto the rear of the connectors. It is not possible to get the assembly out of the case without disassembly as the rectifier on the main PCB is directly behind it, and stands about one inch above the main PCB.

The connection I have made with the crimp terminal is more secure than than the one in the pic looks.
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