Help requested to cure hum problem of preamp

I guess posting some photos maybe helpful

CAT

Dear Cheapie,

One colleague got another Pre-amp from this person. He got the "grounding" problem.

You can check whether you got this problem as well.

1. Turn both Pre-amp and Power Amp ON. Volume can set to low level.
2. By using your finger, knock gently on the metal chasis / body.
3. Check to see if the "knock" will come out through the speakers.

TEST TWO

1. Turn on BOTH Pre and Power Amps
2. Don't connect any source yet.
3. Touch the volume. If the knob is plastic, remove the knob to show the metal part.
4. Touch the volume knob, you will probably hear "sss...sss" noise when you contact the metal knob.

CAT

Dear Accphoto,

These are the photos of my colleague's Pre-Amp. Please take a look and see if you can spot the source of the problem.

Thank you.

CAT

Dear Accphoto,

Thanks for your quick reply.

1. The Ground has not connected to the Chasis. I checked it out for him.
    Even after I connect the ground at the plug to the chasis, the problem
    is still there. I tap on the chasis, the "dong" sound came out from the
    speakers.

2. I can work on the Input wire and the e-caps for him. Will ask him
    whether he would like to spend the money first. No need for really
    expensive caps, right?

3. What is "HT"? You said one side of the HT should be connected to ground
    Please advise.

CAT

Dear Accphoto,

I see. HT = Heater. Thank you.

But I still got one point not clear.

"燈絲( i.e . 12AU7 4 和 5 腳) 加兩支 50ohms 1W 電阻，不用好的，中心落地"

That means ONE end of EACH resistor connect to pin 4 and pin 5 respectively and the other end twisted together and ground it?

Sorry for my lacking in knowledge.

CAT

Yeah, I got this same feeling with Accphoto. I would rather have it soldered.

CAT