STE V1.5 32MHz BOOSTER - STATUS

[exxos]

Still waiting for the PCBs.. But the plastic squares just arrived...

stesq.jpg

[troed]

What's the dimension and needed tolerance of those squares? You're saying that they're really expensive ..

3D printers have very different capabilities depending on how much you spend on them. The one I have (Ultimaker 2) has very good tolerance levels. The first layer gets a bit squished and needs to be filed down but otherwise I've been very happy with what I've printed.

With PLA, which has a substantially smaller shrink effect while cooling down, I got positioning accuracies down to 0.1mm on nearly any dimension, coming mainly from the play of the belts. However, bores will always be up to half a millimeter smaller in diameter than they should and outer contours 0.1-0.2mm larger.

It's nearly impossible to predict. Or it would require a software similar to the software used for tool design in injection moulding. The usual way to go is try and error. Print the part once, measure the important dimensions and adjust the model, print again etc.

https://community.ultimaker.com/topic/5 ... of-prints/

I'd be happy to spend a few hours on seeing if I can get the tolerance level needed (I assume I only have to check for a snug fit in a PLCC68 socket?) if it's a substantial cost saving for you. Unless you already ordered all the plastic you needed .. :)

/Troed

[exxos]

I'd be happy to spend a few hours on seeing if I can get the tolerance level needed (I assume I only have to check for a snug fit in a PLCC68 socket?) if it's a substantial cost saving for you. Unless you already ordered all the plastic you needed .. :)

These squares are costing about £7 each at the moment and I got five of them made with a precision engineering company in the UK.

I did consider 3-D printing them, something I just don't have the time to mess about with... Course of no objection if you want to try :)

These are 24.40mm square, 5mm thick, with a 5 mm rounded corner.. Basically it's just got to fit snug in the socket like the CPU does. Problem is too small and it won't hold the pins on the socket, too large and it physically wont fit.

[troed]

These are 24.40mm square, 5mm thick, with a 5 mm rounded corner.. Basically it's just got to fit snug in the socket like the CPU does. Problem is too small and it won't hold the pins on the socket, too large and it physically wont fit.

Perfect - I'll try to get something done this week. I need to do at least _some_ printing every now and then to justify the cost of the printer ;)

[rubber_jonnie]

So the idea would be that it ends up like a hand assembled version of this:

R244686-01.jpg

Will the idea be that the plastic square will be fixed to the PCB?

[exxos]

So the idea would be that it ends up like a hand assembled version of this:

Yes and no.. If you look at the images in previous posts you can see how it plugs in.. The only issue is this a bit wobbly as nothing to hold the pins in place inside the socket.. It is a pretty tight fit, but need some sort of pressure on the pins to make sure they contact under a little bit of pressure.

Will the idea be that the plastic square will be fixed to the PCB?

Likely not.. We talking factions of a millimetre tolerance , it would be near impossible to do that I think.

The pins on the booster go on the outside of the pins in the socket, those PLCC plugs connect on the inside of the pins just like the CPU does. This is a better idea and method in general, but I cannot do this because I need to solder the CPU onto the PCB and the pins would be pretty much underneath the CPU pins, so be basically impossible to solder together . Not only that, some of the signals are broken and run via the GAL, so I cannot have the CPU directly on top of the pins.. The only methods to solve this is to move the pins away from the CPU, which means the pins push into the outside of the socket on the motherboard...

This is exactly how the 4MB RAM board I also sell works... There is a image which shows it better....



The idea does work, but it is more of a bugger to fit than the proper PLCC plugs. The MMU DRAM board fits in pretty easily as there is only 3 rows of pins, but in this case there is 4 rows, and it is lot more difficult to fit. Though I am thinking of soldering the pins on the bottom side of the PCB making them shorter and hopefully less likely to bend about while trying to insert it.. I have seen this done before on some other Marpet RAM upgrades.. Of course soldering the pins in the first place and keeping them perfectly straight is also a bit of a challenge in itself..

In any case, as there is no CPU in the socket, I use the plastic square is instead to hold it all together and in place.. Of course with the DRAM board, the MMU itself does that job..

[rubber_jonnie]

That is pretty much as I expected, as in similar to MMU adapters. Not dissimilar to the way Alan H's IDE board plugs into the PLCC socket, albeit with a CPU in place.

I guess the question I have, is when plugged in like this, does the plastic square support the PLCC socket spring connectors enough, since it doesn't have contacts that extend outside of the dimensions of the square, like the CPU does, which would normally put pressure on the PLCC socket contacts when the CPU is installed.

I hope the way I explained that made sense, otherwise I'll have to draw you a photograph :o

[exxos]

I guess the question I have, is when plugged in like this, does the plastic square support the PLCC socket spring connectors enough, since it doesn't have contacts that extend outside of the dimensions of the square, like the CPU does, which would normally put pressure on the PLCC socket contacts when the CPU is installed.

Don't know yet :)

I guess if Troed is printing them, he can add the "dummy pins" to the CPU as well if needs be.

[rubber_jonnie]

Don't know yet :)

I guess if Troed is printing them, he can add the "dummy pins" to the CPU as well if needs be.

Fair enough, would be good to see the results from both options. Shame I don't have a 3d printer myself, or I'd give it a go. Maybe later in the year....

[exxos]

12.jpg

If anything, the squares might have to be fraction smaller than the CPU. Square is actually quite hard to fit in even with just one row of pins inserted.