The 42-year-old, who cannot be named for legal reasons, planned to blow up the medical centre as payback against a doctor he blamed for contributing to his blindness.

The man spent more than a year sourcing the ingredients and parts to build the device, which consisted of four cylinders with two timers.

His plans were thwarted, however, when his estranged wife discovered the bomb hidden in a backpack in their garage while he was overseas in April this year.

Police bomb squad technicians who went to the home described the bomb as "elaborate", saying it was capable of detonating.

The court heard the man had repeatedly threatened to kill the doctor, whom he blamed for his descent into blindness.

The man's wife told police her husband first spoke of wanting to kill the doctor in early 2009.

He was subsequently admitted to Shellharbour Hospital's mental health unit for treatment and placed on medication.

However, four months later, the woman said she found a note in her husband's handwriting saying "hire a hit man", prompting her to have him reassessed by the hospital's mental health team.

In November 2010 the couple split and the man moved to southern NSW.

He would often return to see his children, however, staying on the ground floor of their two-storey Albion Park home.

In late 2011 and early last year, the man made two online purchases for three kilograms of potassium nitrate, a key ingredient used to make explosives.

The man's wife told police she found an entry in the man's diary late last year detailing doctors' phone numbers and addresses, as well as a list of chemicals.

It is alleged the man bought items from Supercheap Auto in February this year to use in the bomb.

Police received a tip-off about a possible attack on the doctor in early April and turned up at the Albion Park home on April 4 looking for the man.

However, his wife, fearing what her husband might do to her, told police that he was not at the premises.

The following day the man flew overseas on a one-way ticket.

Four days later, the woman discovered the bomb in the garage, prompting her to call police.

During a search of the house, officers seized several items associated with bomb making, as well as Nazi paraphernalia, including a swastika flag and documentation admiring Adolf Hitler.

Police later intercepted phone calls between the husband and wife, in which the man said: "I tried doing everything the right way and I've been put in the position to do it the wrong way," he said.

"I've got no choice, I've got to do what I've got to do and that's it."

He was arrested upon his return to Australia in August and has been in custody ever since.

Yesterday, his lawyer, Jane Healey, entered a plea of guilty to one charge of making explosives with intent to injure on behalf of her client.

The matter was adjourned to Wollongong District Court on February 14 for sentencing.