How to work out what goes where? Ribbon from print heads

Blacksheep99

Hello, I'm a novice trying to learn how to install a Duet 2 Maestro in to a broken printer. I have an old ST3Di 280 printer where the control board was blown. I'm hoping to upgrade and fix it. So far I've managed the relatively simple part and got the power X & Z plus end stops wired up.

I am now faced with taking the two ribbons from the print head (It's a dual print head so extra complexity.) and working out what goes where. It's this I'm struggling with, how best to approach it? I have a multimeter which may provide some help.

I wonder if others have faced a similar problem? Any advice is greatly appreciated. I've included a few photos which may help show what I'm facing.

Thanks.

Blacksheep99

Veti

it looks like the rib cable was used to go from the controller board and and connect to the breakout board on the hotend.

you could potentially just remove it and wire the parts up directly.

Veti

also the white belts tend to have steel cores.
they could cause trouble.
see
https://reprap.org/wiki/Choosing_Belts_and_Pulleys

Blacksheep99

@Veti yes that’s how it was connected. I have thought about doing as you suggest. I’m fact I think trying to modify a ribbon to accommodate multiple connectors is near impossible and hence I’m left with no other option.

A Former User

This is what I did for a Up Mini 2 conversion:
https://www.thingiverse.com/thing:3465278

As for how to work it what goes where, you can either reverse engineer the PCB at the far end, or use a multimeter to measure out which pins are connected where. Neither of which is a quick and easy method unfortunately.

Blacksheep99

@bearer said in How to work out what goes where? Ribbon from print heads:

This is what I did for a Up Mini 2 conversion:
https://www.thingiverse.com/thing:3465278

As for how to work it what goes where, you can either reverse engineer the PCB at the far end, or use a multimeter to measure out which pins are connected where. Neither of which is a quick and easy method unfortunately.

That’s a great idea with the DuPont. Thanks.

I’ve got the pcb out. I’m trying to reverse engineer to the ribbon pins. Is there a good guide online to explain how a pcb works?

Blacksheep99

jay_s_uk

@Blacksheep99 that should be fairly easy to work out as you can see all the traces

A Former User

The PCB is just an alternative to wires, you can see the copper traces connecting the pins of the ribbon connector to the other connectors (however its possible there are internal layers, which would be surprising, but (at a glance) seems to be unused pins in the ribbon cable if not)

I usually mirror one picture and show top and bottom side by side to get an idea of what the board does; but you could also "just" measure from one pin on the ribbon cable to each of the other pins of the other connectors making a not of what goes where, and work through all the ribbon pins. Its possible multiple ribbon cable pins go to the same pin on the other connectors to carry more current than a single wire in the ribbon cable could do.

Blacksheep99

@jay_s_uk I hoped that was the case. I just need to improve my understanding of pcb's. Are you able to help me with an example? Say taking the E0 motor on the bottom left as you look at the back of the board. Now I know each stepper requires the two pairs of wires. So the four pins on the ribbon connection are the 4 on the left side from the back view, correct? I think I have to work out the tracks on front and back?

Sorry I know I've a fair bit to learn.

jay_s_uk

@Blacksheep99 yes, that's right.
Two pins are on the bottom of the PCB and the other two are on the top.
If you have a multimeter, you can confirm your suspicions.
It'll be worth drawing out an image of each connector so you can mark it up.

Blacksheep99

@jay_s_uk Thanks. I've printed out both pictures and started to mark them up. I have a multimeter so next step is to check the traces. What's the best way to go about that?

A Former User

The meter usually have a speaker-like symbol that beeps when you short the probes, saves you looking at the screen.

if not measure resistance and watch when it drops to near 0

Blacksheep99

@bearer Thanks. I'm making some progress now with this approach. testing my dexterity for sure

A Former User

when doing lots of probing on 2.54mm connectors I tend to take a dupont wire and clip one of my meter probes to a male end, and use the female end to plug onto the pin in question leaving me to only focus on holding one probe.

(or swap male/female if probing a female connector, but then usually remove the housing of the female end of the dupont wire to clip onto it)

Blacksheep99

@bearer Nice tip. thanks