I have personally been on both sides of this exact issue a few times... I think the "return full price" is a line of bull and a bluff on his part. Over the years and moving a few hundred machines I've had this exact quote said to me before when a machine failed after the buyer getting it home. I've even offered it to the seller and had them refuse... Its almost like this type of buyer is expecting a screaming price and a bullet proof machine or for you to answer the call everytime it goes down.
One of my personal experiences, I was selling an 80's Williams game also, to someone I knew and think of as a friend. We had done business in the past and always both were happy. Well, in my bend over backwards days I had offered to bring the machine out to him, cool. A few days later we decide that we can meet halfway when he's in the zone on the weekend and save me a bit of a drive, sweet! Now this stupid 80's William's game had been in my livingroom for months and I had played the crap out of it. Never so much as had a monitor geek or graphic geek, a crappy joystick but played fine. On moving day I didn't know how the weather was going to be so I wrapped the hell out of the game shrinkwrapping it and the whole 9 yards. Long story short, we met, exchanged money and game in a parking lot 1/2 way. When we were moving the game over to his truck I realized that the monitor was loose. We open it up to find that the monitor neck & board was damaged! It was 100% my fault, I didn't check if the monitor was tight and had lucked out when I moved it to my house and around my gameroom. I offer a full replacement monitor as I felt I should have known to check if there were bolts in it. He thinks the tube was OK and just the neckboard cracked, we verify model number, bingo I have a game with one! The next day I pull a working monitor chassis off one of my games from my collection and drop it in the mail to him. Either that night or the next day it takes and ugly turn for the worse! He had gotten the monitor to work but it came up with scrambled pictures! Power supply was bad. The PCB was bad. Now all of the sudden I am being accused of switching pictures, photoshopping working games into my livingroom, selling a piece of garbage that never worked, yada yada yada... WHOA WHOA WHOA! I was going to be bringing this machine to his house originally. I would expect somebody to punch me in the face if I was selling a machine and were dropping it off knowing that it didn't work and I would have to come up with a story when I got there, yet ask full price as well?! I immediately offered a full refund and to come out and pickup the game, but was rejected. What do you do at that point? I'm trying to come out and take the game back yet he wants to keep the non-working piece of crap... At the time and maybe now I believe he was trying to beat me up on price, and indeed it didn't work, but once he had crossed the line of accusing me of intentionally deceiving him and refusing my full refund offer my help stopped, I knew I would be married to the machine.
My most expensive machine to get in my collection was a hell of a long roadtrip. I bought a really nice pinball machine that I felt was a lower end of average price and higher end of quality. Make the drive out, play it, SWEET, SCHWING!!! Drive the 500 miles back home, unload, plug it in, play a few games, proceed to drink coffee and start a marathon play going through the whole night. About 15 hours later the next day when I had to goto work in the morning the machine had already developed a few problems... Didn't even bother letting the seller know, ordered the parts that I needed and I personally figured that I had used the flippers about 1,000,000 times over the course of a solid all nighter and they had probably never seen that kind of use and abuse straight!
What it boils down to is the type of buyer, offer minimal help but do not bend over backwards or take it in the rear end to keep that feel good mushy feeling because you'll feel worse in the end.
Personally I would get a couple of 4116 rams or an old parts board and bring them out to him, and SHOW him how to read the error and how to properly replace the chip. Explain how common a RAM error is on these machines and explain that he must keep his own in stock and understand how to diagnose. Email him a link to crazykong of the manual online. If I was feeling super nice I'd print it off for the person. If he expects beyond that he's being very unreasonable... If he's being accusatory or demanding in any fashion I'd tell him to pound sand since your warranty is voluntary and if he expects bulletproof for under $500 on ANY kind of coin-op machine and he wants someone else to do the work and front the parts repairs he's smoking better stuff than the rest of us!!
