I picked up a Scott A457 integrated stereo amp from a friend who was clearing out a house. It cleaned up nice and plays fine...But I notice it makes a fairly loud pop or crack sound when something is turned on or off on the same power line. I don't have a schematic, but tried a .047 cap, and a MOV across the line, no help. Any ideas out there to quiet this line noise/pop? It does have a power xformer.

:I picked up a Scott A457 integrated stereo amp from a friend who was clearing out a house. It cleaned up nice and plays fine...But I notice it makes a fairly loud pop or crack sound when something is turned on or off on the same power line. I don't have a schematic, but tried a .047 cap, and a MOV across the line, no help. Any ideas out there to quiet this line noise/pop? It does have a power xformer.
:

You will need to isolate where the popping noise is coming in to the amplifier: through the AC line, or into the input jacks. First short out the inputs then see if the noise still occurs; if so, it's coming in the AC line. If not, it is coming through your source audio.
Johnnysan-

Johnnysan, Thanks for the suggestions. Looks like it is coming in thru the 'main in/pre amp' out jumpers they put in the back of the amp. If I run an electric shaver near those inputs, it really generates some heavy static. I guess those buss jumpers, and running the associated lines longer thru the amp become an antenna of sorts.

:
:Johnnysan, Thanks for the suggestions. Looks like it is coming in thru the 'main in/pre amp' out jumpers they put in the back of the amp. If I run an electric shaver near those inputs, it really generates some heavy static. I guess those buss jumpers, and running the associated lines longer thru the amp become an antenna of sorts.
:

You might check the grounding of those input jacks. If they are RCA they could have poor grounds that allow noise to come in.
Johnnysan-

::You might try replacing the jumpers with a shielded patch cord. just a thought,
John
::Johnnysan, Thanks for the suggestions. Looks like it is coming in thru the 'main in/pre amp' out jumpers they put in the back of the amp. If I run an electric shaver near those inputs, it really generates some heavy static. I guess those buss jumpers, and running the associated lines longer thru the amp become an antenna of sorts.
::
:
:
:You might check the grounding of those input jacks. If they are RCA they could have poor grounds that allow noise to come in.
:Johnnysan-
:
:
:
:

There sometimes is a capacitor connected to the AC line input to ground. Find it and replace it with a safety cap (designed to fail open.) Reversing the plug in the wall socket may not prove fruitful, as sometimes they put two of 'em in. I'd personally lose them and rewire to use 3 wire with the green to the chassis.

On some of these sets, it pays to make little shorting plugs (rca plug wired shorted) to any unused input jacks.

Of course spray and excersise the selector switches, potentiometers and tube sockets with deoxit and let it dry overnight. Be very certain to make a map and label your tubes so they go back in the right sockets!

This is a nice vintage set and will be very nice when fixed up. You should replace all the electrolytic and tubular capacitors, and any resistors that have drifted up in value (I'd change out all of them myself, except for the wirewound sand resistors which are probably fine.

Finally if you are not going to use the magnetic phono or tape deck inputs, you can remove the tube(s) responsible for theses inputs and see what happens.

Plenty of help and opinions here.

:::You might try replacing the jumpers with a shielded patch cord. just a thought,
:John
:::Johnnysan, Thanks for the suggestions. Looks like it is coming in thru the 'main in/pre amp' out jumpers they put in the back of the amp. If I run an electric shaver near those inputs, it really generates some heavy static. I guess those buss jumpers, and running the associated lines longer thru the amp become an antenna of sorts.
:::
::
::
::You might check the grounding of those input jacks. If they are RCA they could have poor grounds that allow noise to come in.
::Johnnysan-
::
::
::
::
:
:

If you are going to use a 3 wire AC, you might want to try adding an EMI noise filter.
Here's one:
http://www.ebay.com/itm/6-Amp-115V-250V-AC-Power-IEC-Inlet-EMI-Noise-Filter-/130658137665?pt=LH_DefaultDomain_0&hash=item1e6bd4f641