I'm no expert by far. Avionic, Merrylander and others here certainly are. There is no DC offset on the CR-1020, just idle current. I did a lot of reading on Yamaha threads here before I adjusted mine, there are pictures of the adjustment points and everything in different posts here. Search for "Yamaha 1020 idle current". Basically, if I got it right, idle current is adjusted on the two amplifier boards in the center of the unit. IIRC, there is a TP0 with no wires and a TP1 on each board with either a brown or yellow wire, depending on which board you're on. The TPs are on the front end of the boards and next to each other.
Before I adjusted my unit, I played about 3 hours of tapes on it at a medium level, easy listening. Then I zero'ed out or defeated all the adjustments so it was flat neutral, centered the balance, turned the volume completely down, switched to an unused and empty phono input and waited 10 minutes.
I carefully put mini clips on the two TPs of one board and used a non metallic screwdriver on the pot that is on top of the same board and to the rear to adjust the idle current to 10mv. The pot is really sensitive and a little adjustment goes a long way, so take it easy. I played 90 minutes of tape, set up the unit and then checked the adjustments again. For some reason, they were about .3mv high (10.3mv), so I backed them off, played the other side of the tape and went thru the whole process again. This time they were right where I had adjusted them so I called it good. One board came out at 9.9mv, the other at 9.8, that was good enough for me.
Avionic suggested cleaning the pre-amp switch on the back of my unit, so I did that and it helped with the speaker output and clarity, I think. I don't use headphones, but I'd bet there's probably some corrosion in yours (and mine too). If you sprayed some Deoxit in the holes and then inserted and removed your phone jacks a few times, turning them a little while they're seated, before the Deoxit dried out, it would clean them up, but maybe someone with more experience has the definitive answer. You might do a search on that too. Good luck, I hope your unit comes out sounding as nice as mine, it's been playing almost non-stop since I finished it and it seems to sound nicer every day.