sansui ba 3000

[maclvrbr]

After the amplifier has been on for approx and hour the speakers develop a high static noise coming through them. This has happened with multiple sets of speakers being used to rule out x-over. Any ideas where to begin diagnosing, thanks

 

[vigman]

Does it happen with the front volume knobs turned all the way down ? What are you using for a preamp ? What is the history of the amp , recent service , restore.,E bay or found in grandpa's garage special?

 

[maclvrbr]

I have not checked with volume knobs fully CCW or at zero. I am using a mcintosh mc 28. No history on the amp I acquired a year ago and have been using it one a dy since then. I suppose I could incorporate another amp to rule out the preamp. Ideas?

 

[vigman]

Running an un serviced BA-3K ( or anything of that vintage ) could be a costly mistake, Checking bias ( and it's stability ) would be a must. If nothing else IF YOU HAVE THE SKILLS.... inspection of the Regulator board ( cold solder joints, clean pins ) and same for the driver board..There are some OL SKOOL semis in the front end that get noisy over time.... These amps are SO GOOD when all is well.. Another note is to find the serial # and somewhere around here is a lookup table for the production build date.. the early ones have additional issues on the driver board. Some of them have extra jumpers between the driver boards and it's mother board to prevent against pin failure.....

 

[vigman]

If the volume ( actually input pads since there is no gain ) is turned all the way down & the amp is up to temp, and no static, your problem is up stream...

 

[LBPete]

The BA-3000 is one of Sansui's best. Please post the serial number for the database. Click on the link in my signature block.

- Pete

 

[Overundr1]

Unplug the pre amp and see if the static continues
Will rule out that part of the chain

 

[maclvrbr]

Thanks for the ideas, Will check bias and dc offsett clean plug connectors as well. thanks Lee will unplug to rule out any other component.

 

[JOMARK911]

I own two of these. Before you do anything else, while static is happening select and deselect subsonic filter a couple of times. Like ON then OFF. If it stops , your problem is in the filter board that lies below the power meters.
Then we talk.

 

[maclvrbr]

I have let it run without an input for at least 2 hours without issue. I will continue to monitor it however may be looking at my preamp as possible culprit

 

[vigman]

I would now run an iPod or something external to see if the failure is under load or higher temp....

 

[maclvrbr]

Ok the issue is definitely in the amp with no input connected . When the static begins the left meter jumps with static. I pushed the filter buttons with no change.

 

[vigman]

Rebuild time !

 

[maclvrbr]

I would like to isolate the issue in the left channel first

 

[vigman]

1st yo have to check if there have been EXTRA wires soldered to your 2705 board... do you have the schematic?

 

[maclvrbr]

S/N 245060187

 

[maclvrbr]

Do you mean 2507 board? I do have a schematic.

 

[vigman]

Some " repair " shops added extra wires between the 2512 board and the 2507 to make up for possible pin failure... If you have those wires you cannot remove the 2507 for bench testing / visual inspection.

 

[maclvrbr]

There are no wires added to this board. I will remove and check all solder joints ( reflow) and clean pins at connector joints.

 

[vigman]

Check for tightness on the 2 final transistors on the 2507... AND whatever screwdriver you are using to remove re install the phillips that attaches that 2507 to the chassis INSULATE IT !
Piece of shrink tube, electrical tape , SOMETHING.... If you touch the transistor tab to ground ( either one ) you will have a bad day!