Mike Sen had been retired for a couple months from Honolulu-based Senetics when the Bank of China came calling for help.

The country’s third-largest bank had a problem. Its main vault door at a repository in an unmarked building in Shanghai could barely budge, and it was taking three people to open it instead of one. The vault is where all the cash for Bank of China branches in Shanghai is stored, and the government-owned bank couldn’t find anyone in China with the expertise to fix the door.

Sen, the former CEO of Senetics, Hawaii’s largest security safe and bank equipment company, said the 15-ton, American-made door had been installed in the 1930s, and its measurements were based on a fractional decimal system rather than the metric system used in China.

That meant all the tools and parts needed to repair the door had to be based on the fractional system, including the ball bearings and rotor bearings, Sen said. The door was 17 inches thick of solid steel, or 23 inches including the bolts, and was 7 feet tall and 4 feet wide.

"I guess we were the closest in the United States to Shanghai that could take care of the repairs, so we got a call," Sen said. "The door is American-made, so it required some American expertise or people with American vault doors to do some repairs on it."

After nine months of troubleshooting through discussions and emailed photos of the door, Sen diagnosed the problem as being the bearings in the hinge. So Sen, 72, and his stepson Reid Takeshita, 47, left last month for Shanghai with different-sized ball bearings and steel rods to do the repair work since they didn’t know the exact size of the door’s internal components.

But when they removed the hinges to look inside, they discovered that not just the bearings, but the top and bottom bearing plates were cracked. They had to remove the bottom hinge, half buried in concrete, to get to the plates.

Since Bank of China’s vault had three entry doors, Sen and Takeshita thought they might be able to borrow plates from one of the other, rarely used doors until parts could be ordered from the U.S., but upon closer examination they discovered the plates were cracked in that door as well.

"So we had two doors now that had the same problem, and we searched for about half a day to locate a foundry in Shanghai to fabricate the hardened steel bearing plates inside the hinge for us," Sen said. "We were lucky to find a foundry in Shanghai to do it. They did it in three days."

The whole repair job took Sen and Takeshita a week and a half.

Senetics, which was founded and is owned by Sen’s wife, Frieda, started operations in 1977 and has 23 employees for its two divisions. One division sells, installs and services office furniture, and the other division sells, installs and services high-security safes and bank equipment. Senetics services about 80 percent of the financial institutions in Hawaii.

In the case of the Bank of China’s vault door, Sen said it was unusual because the back side of the door had identical controls as the front side. So someone accidentally locked inside the vault could open the door from the inside, Sen said.

"Most vault doors don’t have an emergency device on the inside, not bank doors anyway," he said.

Accessing the vault was like a scene from a movie, Sen said.

He said armed guards with shotguns stood outside the entry to the vault area. Getting inside the vault was even more intense.

"We had to go through several man traps and a sliding steel door before getting to the main entrance to the vault," he said. "For the man traps, you enter one door into a little space, then close the door behind you, and then another door opens. No two doors are open at the same time."

He said bank employees watched them the entire time they were on the job.

"We could see all the cash being sorted, counted and bundled," he said. "I stood in front of millions of yuan. Unfortunately, they wouldn’t let us take any pictures (of the cash)."