Hiss in HD130 410

I just picked up an HD130 410 for a great deal. It had been sitting in a basement for quite some time. It was pretty grungy, but powers up and sounds good. The only issue that I'm having with it is that I have a fair amount of hiss as I turn up the master volume. If I turn the master up to 10 and then gradually increase the channel volume, the hiss does not increase as much. If I turn up the channel volume to 4 (about where I like the sound) and then turn up the master, the hiss gets much worse.
This amp has probably never had any maintenance done to it whatsoever. Still has the big bottle Sylvanias, I'm sure it hasn't had a cap job.
I am okay at "remove and replace" type repairs and rebiasing, but diagnosing a problem is not where I excel. Any ideas what I should look at to try and track down this hiss?

Forgot to mention - this one is the solid state phase inverter.

Noisy preamp chips? Don't know. Not knowing what you are expecting. There is a certain amount of hiss with amps but I don't know how to describe what is NORMAL. You might try unplugging the IC's and plugging them back in to clean the chip contacts. You sure it's hiss and not dirty pots?

The pots are a little scratchy. I haven't hit them with contact cleaner yet. It's not just as I'm turning the knob though, it's constant. I'll try cleaning the chip contacts, maybe just remove everything that is socketed and clean it up. Hopefully I can do that this evening or tomorrow and give an update.
This is definitely more hiss than I would expect for the volume level of the amp, considerably more than my 210-65. I'm excited about this amp. It looks like everything is original down to tubes. But that probably means I have some work ahead of me to get it sounding right.

When yo remove the chips, make sure you mark how they are oriented. They are easy to confuse.

Cool, thanks for the tip. I'll mark them with a pencil.

Mike, you did it! Cleaned the pots and the IC and transistor sockets, now the thing is nearly silent at idle. Thanks so much!

Good to hear. Glad you got it working right. Mike.