I hope someone may help as I read a book a good 30 years ago which I believe was three series consolidated into one book (the book had a blue cover and edge of pages were a yellow colour).
That was The Complete Venus Equilateral by George O. Smith, which collected the short stories and novelettes of his Venus Equilateral series in book form. There were several editions issued between 1975 and 1980; does any of these covers look familiar?
Anyway in the book it started with men finding Martian energy transmitters,
The Martian energy transmitters are found in the story "Lost Art" (from Astounding Science Fiction, December 1943, available at the Internet Archive). Quoting the Wikipedia plot summary:
Martian archeologists Carroll and Baler discover an ancient Martian electronic device. After getting the device running and experimenting with it, the two are able to deduce that the device is a relay unit for a wireless power transmission system. The Martian relay becomes the basis for power transmission networks throughout the Solar System.
these later were used to develop replicators
Quoting the Wikipedia plot summary for the story "Special Delivery" (from Astounding Science Fiction, March 1945, available at the Internet Archive):
Wes Farrell, now employed at Venus Equilateral, uses the Martian power transmitter to construct a matter transmitter. Kingman sues on behalf of Terran Electric, arguing that the matter transmitter is essentially a power transmitter, and thus falls within Terran Electric's licence. Channing successfully argues that the device is not a transmitter by using it as a matter duplicator, to create multiple copies of the judge's antique watch.
which caused a problem as the economy went haywire till they discovered an element which could not be replicated
Quoting the Wikipedia plot summary for the story "Pandora's Millions" (from Astounding Science Fiction, June 1945, available at the Internet Archive):
Now that it is possible to duplicate money and precious metals, an economy based on scarcity collapses. The people of the Solar System must fall back on barter, and those too poor to buy matter duplicators are left to their own devices. It is not until the staff of Venus Equilateral invents a material that cannot be duplicated that a monetary system can be re-established.
(it blew up the replicator they were doing this on).
Quoting from the text of "Pandora's Millions":
"Nope. We came to give you a hunk of something interesting. Wes Farrell hauled it out of space, electrons, and considerable high-powered theory. Identium. Corrosion-proof, inert, malleable, but hard enough for coins, and you can roll it out into ten-thousandths sheets and use it for paper money. But don't ever put it into a duplicator. It'll blow the top right off of your roof if you do. There's our medium of exchange, Keg."
From then the economy developed (a friend of one of the main characters bought his space shipping line back because of this). The book ended up with the main characters developing teleporter (like Star Trek) with the use of the Martian energy transmitters discovered at the beginning of the book. These were then used to transport two newborn babies who were ill to another planet to get medical treatment.
The babies are transported in the story "The External Triangle" aka "Interlude". Quoting the Wikipedia plot summary:
Twenty-seven years after "Mad Holiday", the Channing and Franks families live on a thoroughly terraformed Pluto, and the Channings' daughter Diane is married to the Franks' son Jeffrey. Don Channing, Walt Franks and Jeffrey Franks get together to try to come up with a teleportation device that will allow original objects, and not just their duplicates, to be transmitted across interplanetary space. They succeed in teleporting mice from Pluto to Triton, but the mice only live for five minutes. The plot thickens when Diane Channing Franks' newborn twins need urgent treatment for a blood disorder, and only the teleport can get them that treatment. Don Channing finally realizes that the teleport system was inverting the mice, and that their inverted hemoglobin was unable to carry oxygen, leading to their deaths. By teleporting an object twice, the inversion is cancelled out, so the twins are saved by teleporting them to a hospital on Earth via a relay on Triton.