Science Of Cambridge MK14 Replica build

[stephen_usher]

[rubber_jonnie]

OK, so ultimately it's a fail for the PCB.

All is not lost however as I have plenty of board left so I'll try again.

Main issues?

Well the pads broke apart whilst drilling, so I need a smaller drill bit that's for sure, and I think at least for the sockets, I need a jig to drill the holes, but that's a small issue and easily sorted.

I also need to be sure I have a good enough layer of etch resist too, though it was mostly fine.

[rubber_jonnie]

OK, so I went for it with a 2nd PCB

Better results this time for sure:

IMG20241110185822.jpg (155.65 KiB) Viewed 336 times

That's not to say there aren't issues because some of the long traces coming from pins 5 & 6 really thinned out despite having the same amount of etch resist as some of the other thicker traces.

However these are easily repaired and there aren't many of them.

What helped massively, and you can see the through holes are much more precise, is that I used protoboard as a drill guide/template and the 0.8mm drill was perfect for the holes, which I drilled before etching, so there was no danger of the drill tearing the pads.

What I may do is use this one as a drill template for another couple of PCB's and look to get a better etch resist pen before making any more as it isn't the best. I'll test on some spare PCB to find the best options before etching too.

[rubber_jonnie]

Well, it's been a while me getting round to testing, but my tape interface for the MK14 works!!

It's a little sensitive to volume, but once you get there it works just fine and I can repeatably load data to a specific spot in memory

I'm going to come back to the PCBs as I need a better etch resist, as the one I received is just a permanent marker, so I'll do some testing with alternatives, but otherwise it's progress all along and I can use the PCB I just made as a drilling template for another two PCBs now I have a small bench top pillar drill and some decent .8mm bits

[PhilC]

Have you tried the toner transfer method? You need a laser printer, some glossy paper and an iron

You simply print out the circuit in mirror image and then use the iron to transfer it to the copper PCB.

Oh and you can use less chemicals by dabbing it on with a sponge rather than bathing the PCB in the etching chemical.

[rubber_jonnie]

Have you tried the toner transfer method? You need a laser printer, some glossy paper and an iron

You simply print out the circuit in mirror image and then use the iron to transfer it to the copper PCB.

Oh and you can use less chemicals by dabbing it on with a sponge rather than bathing the PCB in the etching chemical.

I don't have a laser printer any more so that's not something I can do, unless it's possible to do with an inkjet. This would be ideal, I did watch a Mr Carlson's lab that showed this process.

Dabbing with a sponge would be possible but I suspect it would take a very long time to etch.

[stephen_usher]

Yay! It lives!

[rubber_jonnie]

Yay! It lives!

It does!!!