inside a cheap eBay 1 to 8 way DMX buffer.

I thought it would be worth looking in one of these units to see if it follows the rules for proper buffering of a DMX512 (one direction RS485) lighting network as used in the theatre and show industries.
It turns out that the circuitry is quite standard with a proper MAX485 receiver and 8 matching transmitters, but it's also a bit odd in that the circuitry is clearly based on a fully isolated buffer, but with the isolation defeated by the use of a single power supply.

With an application like this I would recommend swapping the supplied power supply for one from a reputable supplier. That way you can choose one amply rated for the task, plus avoid any isolation issues that could cause data corruption or damage other devices on a network.

Here's a typical search link on ebay com to find these units. :-
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_sop=15&_nkw=8+channels+output+dmx512&rt=nc&LH_BIN=1

If you enjoy the channel you can help support it with a dollar for coffee, cookies and lighting gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm