People often dismiss Gobots as unsuccessful and obscure, and in the grand scheme of things it probably is. But the received wisdom of the Gobots line as 'the other transforming robot line' is a little false, as back in the mid-1980s it seemed everyone was trying to do the same - Buddy L had RoboTron, Ertl had Pow-R-Tron, Tomy had Super Alternators, Remco had Zybots, Mattel had Powerbots and so on.
The bronze medal, in America anyway, arguably went to Select's Convertors line. This only lasted a couple of years (something like 1984-1985, the boom years), and had no media tie-ins, but is still remembered fondly by a small clutch of collectors. At least, the moulds are generally well-known - outside of North America, the figures were released in a hotchpotch of lines, and a lot of people probably own moulds related to the series without even realising it. The moulds were all licensed from a Japanese company named Mark, who specialised in licensing figures from other manufacturers and making cheap, plastic versions of them, though they also designed some figures themselves.
The first series, released in late 1984, consisted of already extant Mark designs. The series' scant mythos pitched the heroic Defenders against the evil Maladroids, with the former protection Earth from an invasion by the latter. It would seem the Convertors were largely intended to be sentient robots - while some packaging refers to the Defenders being created by "Earth's central computers", they do all have brief personalities listed, and no mention of human operators.
Four different assortments of Defenders were issued. The all-plastic standard Defenders figures numbered four - three were taken from Mark's version of the Dorvack figures, with the fourth (First Track) being a re-release of the same company's version of the robot from Sasuraiger (Takatoku's original toy is better known as Batrain). Around the same size were the Motorized Defenders, added towards the end of the series. There were two friction-powered, boat-based moulds, each recoloured as two different characters (around this time, Select re-released the other Defenders in new colour schemes as well). I'm not sure at the moment if these were pre-existing or designed for the series, but it's likely they were Mark designs either way. The Super Defenders were four larger figures with diecast parts, all taken from Mark's toys for the anime Super High Speed Galvion. Finally, there was a single Jumbo Defender - Bull - of uncertain origin. This featured diecast parts and was the largest toy in the Convertors range.
opposing Maladroids had to make do with just two ranges. The standard
Maladroids were around the same size as their Defender counterparts, and
again four were issued. Similarly, they were drawn from Mark's budget
figures based on Takatoku designs - in this case, figures from Macross
and Orguss. Continuing the symmetry, later in the year Select devised
their own colour schemes to replace the Mark colours on the first batch
of figures. The other range was the Motorized Maladroids - these also
used friction motors, but were much smaller than their heroic counterparts,
being four versions of Mark's super-deformed Macross Valkyrie figure.
As well as the Defenders and Maladroids, there were two other subgroups to the line. The Mini Bots were four small cars "created as local defense systems to aid the Defenders locating Invaders that may have gone undetected". The figures were taken from Mark's Robo Car line, and contained diecast parts. The other were the Spies - small versions of household objects taken from Mark's Gokin Robo series. While the four figures were unaligned, their short bios painted them as mercenaries at best, devious bastards at worst. The two Mark lines are notable for obviously being an attempt to cash in on Takara's recent Diaclone Car Robot (Robo Car) and Microchange (Gokin Robo) lines - while being much smaller, and unique designs, a number of alt modes and colour schemes were the same.
Convertors managed a fair measure of success presumably - most transforming robot lines did from mid-1984 to 1985, as Transformers kicked off a craze Hasbro weren't prepared for, and there weren't enough of their own figures to satisfy demand, meaning kids would often settle for something else. It certainly did well enough for Select to commission a batch of new moulds for 1985.
The Defenders and Maladroids made way for the heroic Avarians and the evil Insectors - themed as transforming into birds and insects respectively. Five of each were made - the majority seem to be new moulds, though two Insectors used Mark's version of figures from Takatoku's Beetras line. The two sides even had a vacuum-formed playset made - this was bundled with four figures from each faction, which can't have helped sales much even if it was a generous (desperate?) move.
They were joined by new figures in the Mini Bot and Spy brackets. For the former, Mark's designs followed the same transformation as the first releases, but based on vehicles more likely to be found on American roads (the assortment was even patriotically renamed 'American Mini Bots'). The New Spies also took a change of tack, with the robots turning into working amusements (well, and a till) - I'm not 100% sure whether these were designed for Convertors, or taken from an existing Mark line. They do bear the Select stamp like most of the commissioned designs (anything Mark had produced prior to working with Select seems to be unstamped, making identifying bootlegs fun), but who knows how this pair of bottom-feeding companies worked...
Sales weren't as good as the initial transforming robot boom turned into a mild bust. Hasbro got their act together with Transformers, and the high profile series began to assert itself over the copycat lines (and the pre-existing - just about - Gobots). To carry on with the common sense assumptions (that are most likely wrong), my guess is that the 1985 series didn't sell as well, and Select cut their losses rather than commissioning more moulds from Mark.
Sadly, many of the toys were very cheaply made, and while they're a lot cheaper than Transformers or even Gobots on the secondary market, finding examples of many that are in good condition is tricky. While the figures are a mixed bunch, the line explored some territory its' competitors didn't, and is a fun bunch of curios to collect.