Equi=Core Hum & Other Issues

@jea48  Jim, thanks for responding.
I'll answer as many questions as I can...
Philly rowhome built in 1939, new electric inside. Since I kept you in the loop during my upgrade, I know it's all up to code.

Meter socket is on the outside of the house flush against the wall.
There is an overhang above the meter (extension of the kitchen) so meter always stays dry.

All houses are attached with flat roofs. The pole feeds the first house on the block, then 
power line runs along each structure close to roof with small transformers mounted on side wall.

The drop attaches from this to my weather head which looks like a square box bolted to wall. Conduit runs downward mounted with U-clamps. Only the drop wire is exposed. 

Conduit travels 25' down then turns under the kitchen overhang into top of meter. Outside of meter is in good condition, corrosion is on wiring and contacts inside, one leg only.

Meter has heavy cable travel through exterior wall directly to service panel. This cable in good condition.

Electrician says the water leak starts at the top after the drop.

Appreciate the help Jim.

@cleeds 
It's clearly spelled out; the power company's responsibility ends at the drop.
They are responsible for the meter and not the pan.

I appreciate your help and empathy.

@lowrider57


Picture.
https://www.pinterest.at/pin/160300067962784594/

The picture shows a typical fed overhead electrical service where the meter socket and mast pipe are surface mounted. (Yes I know yours is concealed with a semi- flush mount front meter cover.)

What I want you to look at is where the power company’s triplex cable connects to the mast pipe. (May be in your case to an eye bolt).... Note in the picture the triplex is supported by an insulated mast clamp. Notice the mast clamp is below the bottom of the weather head? The point of attachment of the triplex must be below the bottom of the weather where the service conductors exit the weather head. That is a must!

Looking at the picture.
Next notice the loop, (called a drip loop), in the service wires that exit the weather head that are connected to the triplex. See the drip loop? The drip loop is a must! When it rains the rain water that collects on the three wires runs to the bottom side of the loops and drips down off the wires. If the point of attachment of the triplex is above the weather head that increases that side of the loop and will cause the rain water to run up into the weather head and run down the outside of the wires inside pipe onto the termination lugs of the meter socket. (Water seeks its’ own level)

Next go outside and look at your service.
Is the triplex attached to the structure above the weather head or below the weather head by around 6" to maybe 12"?

Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the bare neutral conductor that enter the weather head.
First the terminations should be below the weather head. That is must. If not if rain water can enter between the insulation and the stranded wire conductor the insulation jacket will work just like a siphon hose and the rain water will run down the inside of the insulated conductors and run out onto the lugs in the meter socket.

If you can, explain what the terminations look like.
Example. Inline hi-press sleeve type splice. Maybe like this?
https://www.gordonelectricsupply.com/p/Burndy-Es2W2W-4-4-Alcu-Sec-Sleeve/5674716?gclid=EAIaIQobChMIq...

OR???

Jim
.

OK @jea48 . 
 I can clearly see the drip loop and it's exactly like the one in your picture. I'll need to use my binoculars to see the rest.

So, I'll check that the mast clamp is below the bottom of the weather head... 6" to 12"

Next, I'll look for the triplex
terminations. And they should be below the weather head.

Now I understand how this design keeps water out of the conduit.
Will report back tomorrow.
Thanks Jim!

CORRECTION:

Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the bare neutral conductor that enters the weather head.

That should read:

Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the INSULATED neutral conductor that enters the weather head.

Sorry about that......

(Insulated neutral conductor will more than likely be black wrapped with white marking tape.)

Jim