Hiss in old Panasonic amplifier

[CivicProtection]

I got this shabby looking Panasonic at a thriftstore.
Covered in grime and dust. Paied $8. Brought it home switched it on, works.
The tuner is actually really nice, the dial is full of stations even without an external ant. Bought some Pledge spray same time as the unit (for the unit)
and picked one with more conditioner. The wood solid aluminum and glass were all polished and it looks nearly new, beautiful craftsmanship from another era.

Back to the original point: it is a Panasonic Stereo RE-7070C.
27 transistors 17 diodes. RCA jacks for speaker output and only one input, phono in. The unit has an 8 track player.

I hooked it up to the computer and it works, but though my headphones, the ones I talked about in another thread here, there is a loud hiss, the bass is "flabby" and the sound is meak, not volume, the sound is meak. Don't know how to describe it.

Being it is PHONO IN, could it be that that is the problem? Feeding
the audio in there? I opened another amp earlier and I looked at the
"aux in" and "phono in" inputs inside. The "phono in" had resistors all over it and the "aux in" did not. If I feed my mp3 player into the "phono in" it sounded like ****. That might account for the flabby bass.
By the way when I switched over to FM-Stereo, the sound sounded great, but the hiss was still there.

It will never have a record player hooked to it, if I reopen it and find a mass of resistors hooked to the "phono in", can I remove them and recolder the wires back t o the terminals for an unresisted connection? And what would happen IF a record player were hooked to the moddifed input?

Anyways it is nice wood, chassis is built like a tank, thick steel sheet, the front is made from thick aluminum and good plastic dial. It has lightbulbs.
Maybe from late 60's 70's?

Thanks for any help and feedback!

[CivicProtection]

If it means anything, I opened the back and attached to the chassis near the back panal I just removed are a pair of Matsushita 2sb473's.

I forgot that glued to the inside of the wood cabinet is a complete schematic diagram and diagnostic instructions. Wow.
There really was a time where companies gave a s.h.i.t........!

[CivicProtection]

One modification that has to be done, is adding a capacitor to the power switch!
It has non I assume, as it makes a loud ear busting POP! when I switch on with the headphones on my head. Might add caps to other controls don't know, but the power switch is a must.

Don't be shy; POST

[jaycee]

Flabby bass and hiss is probably due to worn out capacitors.

The Phono In will have RIAA correction on it, which will distort the sound of a line in signal - also it probably has amplification for a MM cartridge which would clip with a line in signal.

[ampimp]

Jaycee is right
You are overloading the phono input with a line level signal .
The hiss you complain of on fm radio is more than likley to be the result of a weak signal. A good and properly alignd fm antenna will give much better sound quality.
Regards ian