Absolutely. the only difference between a 3 running the Rev E and a 4 is the enclosure and where the board was mounted. otherwise they were/are identical when new.
Pull the enclosure off of the 4 and it would look almost identical to your 3.

setting up the Rumba is a pretty easy process, but will require you to flash the firmware to it.
You will need to change the connectors for the thermistors, but all others can use the screw connections.
If you need help with any of that, just ask.
oh yeah.. you will most likely need to drill a new hole or two to mount the new board, too. again, pretty easy.

1. Geeetech anything is usually garbage. made with the cheapest components that can be found, assembled by what amounts to slave labor.

You are probably right in regards to the slave labor thing but I have bought great quality stuff from chinese suppliers.

I was just trying to find the family of board that the Rev:E is compatible with and this board looks practically the same except may be the connectors. That is why I was looking at it. Not because it was cheap.

Point taken but again i have bought some great quality stuff through that site.

http://wiki.solidoodle.com/multimeter-testing here is where I got that image.

OK would it be as compatible to the SD3? I am cool with going ahead with that plan just to get it back to functioning as it did.

I have since noticed I have some life in the board. The heatbed is heating and the hotend is heating, hotend fan is running and the thermistors are reporting accurate temps to the screen (laptop running repetier-host connected via usb). It is localised to a problem sending commands to running the motors X,Y,Z and E.

Cheers for the response.
I appreciate your time.

Cyberfez

2. cheap stuff is just that - CHEAP. it will not last. If you are ok with replacing every 6mos to maybe a year, go ahead. If you want to only do it once and be done with it, be prepared to spend a little more.

3. if you want quality parts, do not shop on Aliexpress.

4. not sure where you got that pic for checking voltage, but it is definitely the wrong way of doing it, which is most likely why you are now looking for a replacement.

so, i have two SD4s running the Rumba board i linked above. They have been running on said boards for several years, trouble free. The one has more than 2000 hrs of print time and still going strong. the 2nd one is probably around 1200 print hours. Both are reliable workhorses.

then nothing worked.

My personal choice is still a genuine Rumba, but there are a multitude of others out there.

whatever you decide, do your homework, and buy from a reputable source - somewhere that offers some kind of guarantee/warranty for the potential doa.

The  led is lit on the mobo.

no smell of magic smoke or anything.

here is a video of the original issue - https://youtu.be/NtxZoumyfes

What should I try next? What usually blows in them?

If I am up for a new mobo - what will drop straight into my Solidoodle 3?

Here are the images of my mobo.

Cyberfez