Sony saw40 sub problem

[Scott_drake]

Hi

I just brought a second hand Sony saw40 subwoofer. at low volumes the sub sounds alrite, (unsure of how it should sound). But as the volume is increased it seems to make a strange noise, as if the sub is bottoming out or clipping. ( Im sure its not bottoming out) This seems to only occur at some frequencies am thinking of replacing the filter capacitors and rectifying diodes incase something is faulty in this area. I may also replace the two power Transistors ( mn2488 & mp1620) with replacement type ( 2sd2488 & 2sb1620 )

Does anyone know what this noise could be? Is it a good idea to replace the 6800mF with 8000mF. Or would it be best to put the new caps in paralel with the old ones for more capacitance.

Thanks in advance for any input.

Scott Drake

[Scott_drake]

Hi

I have now replaced the output transistors and the power rectification diodes. I started the sub up and YES there is much less of this "clipping noise" at high volumes. But im still not fully satisfied with the performance. As this is quite an old sub would it be best to also replace the filter caps with ones i previously talked about?

Would i put these caps in paralel with the old ones for more capacitace or just simply replace them?

Please help


Scott Drake

[gni]

If you are going to take the time to work on the Caps. . .replace them!

If they are in the Power Supply, it will clean up ripple and give a
better, stable DC voltage for the amplifier to amplify.

I would check for mechanical issues. . .especially in a sub.

Chris

[Scott_drake]

Hi - Thanks for the reply, what do you mean by mechanical issues? what should i be looking for?

[gni]

A subwoofer by nature must move a large volume of air
in order to produce sound at low frequencies. The bolts that hold
the woofer in place can come loose. The driver itself can "ring."
Parts on the driver (solder plates) can buzz and rattle. The box
itself may be old and the glue is failing. The electronic parts may
be vibrating and adding noise to the output.

All can be solved. . . gentle pressure to various part while operating
can usually detect the mechanical vibration. . . gunk the bad areas
with something to deaden the vibration.. . sheetrock screws work
well for glued cabinets that are coming apart.

That about does it. Had "noise" problems with a pair of JBLs a few
years ago. . .did all the above. . .and gave another 6 years of life to a
pair of loudspeaker.

Chris