I repaired a dead channel and some distortion in a Marantz 4220. After a recap of all the boards except for the ones relevant to the fm/am boards. Replaced the output transistors which were originally 2sc790 for new tip41 transistors. Also replaced the ic originally they were toshiba ta7109p in the right and left front channels. In the left and right rear channels there were toshiba ta7109ap. All four for were replaced with unused toshiba ta7109ap ic. The dead channel was in the right rear. Now the all channels are alive and working after the recap and new semiconductors and toshiba ic. My question is. Before I do my audio adjustments. I have read on some posts that using the new ta7109ap there has to be a 2k trim pot put in the r755-r758 positions on the amp board, for bias. Originally my amp board had no resistor or did it have markings for r755-r758. The schematic I aquired said that those should be a 15k. I found a place to install them, which would connect pins 5 and 6 by way of a 2k trim pot. But since this receiver a marantz 4220 already had the ta7109ap installed with no resistor or trim pot. Should I not even install the 2k trim pot. I just didn’t want to go into all this work and waste it by not putting this trim pots in, and ruining the work i have done. The pictures are of the original board before the recap and new ic. Also a picture of the schematic and amp board from the service manual. I hi-lighted the location of where the trim pot is supposed to go. Is it needed when switching from the toshiba ta7109p to the toshiba ta7109ap?