Smonson's slow H4 build

[rubber_jonnie]

Sometimes using a reclaimed chips can be a pain in the a%% getting all the pins in the holes. I purchased this pin straitner that helps a lot getting all the pins aligned so they cane inserted in a socket.

https://www.jameco.com/shop/ProductDisp ... ctId=99363

@PaulJ Hmm interesting. At the moment I use a pair of small pliers with a flat, parallel nose, it works very well, but I may invest in something like that.

[PaulJ]

@PaulJ Hmm interesting. At the moment I use a pair of small pliers with a flat, parallel nose, it works very well, but I may invest in something like that.

Its not perfect but it really improves your chances of getting a used chip in the socket without going crazy. The pliers were my old solution but does work better than that.

[rubber_jonnie]

@PaulJ Hmm interesting. At the moment I use a pair of small pliers with a flat, parallel nose, it works very well, but I may invest in something like that.

Its not perfect but it really improves your chances of getting a used chip in the socket without going crazy. The pliers were my old solution but does work better than that.

@PaulJ Yeah, I can imagine they help massively. I recently got a proper chip puller, it works great for TOS ROMS and anything up to about DMA/Shifter/AY size. Bit expensive (£33!) but worth it IMHO.

Actually, I also got a cheap Chinese chip puller off eBay that was only about £5, and it isn't too bad, but it isn't as easy to use as the other.

[Smonson]

So, I started on my el-cheapo EPROM programmer. Gonna use an Arduino Mega, since it has lots of IOs and a USB serial port, and slap a bunch of voltage regulators on it since you need 5v (for normal reading), 6.5v (for program verification), and 12.5v (for programming). I'm going to generate these voltages from adjustable LM317s. From Jaycar, the Mega and the shield are $63 AUD ($40USD). I think I have everything else I need on hand.

Wiring up the PLCC-44 is going to be a bit of a job.

eprom-programmer-1.jpg (86.11 KiB) Viewed 5397 times

[Smonson]

The programmer works - not quickly mind you! But considering that it only comprised about $20 USD in parts I'm not complaining.

I have to erase the chip again now

[PhilC]

To quote Hannibal from the A team, "I love it when a plan comes together "

[Smonson]

To quote Hannibal from the A team, "I love it when a plan comes together "

Classic!

Here are the final pics with the interesting wiring underneath. I had to cut a couple of analogue pins off (analogue! hah! who needs 'em!) to fit all the wires through the gap.

Whoever designed this IO board shield with the wiring connectors on the far side of the inter-board connectors is now on my people-to-murder list.

eprom-prog.jpg (173.56 KiB) Viewed 5347 times

eprom-prog-underside.jpg (166.33 KiB) Viewed 5347 times

Tell you what I should have done: worked out which pins go to which IO ports on the ATMega 2560 before I wired this up. I probably underestimated how much extra time would be wasted shifting bits around to get the right data to go to the right pins. Patience is a virtue I don't have time for

[Smonson]

It's so close, I can smell it. It smells like... burning PVC.

I have RAM and I've burned TOS into the second half of the EPROM (I hope that's what the jumper near the ROM socket does). I seem to have lost my optocoupler but it's on the manifest so it's gotta be somewhere in the garage, perhaps on the floor???

I've done all the mods apart from the 470-ohm DMA resistors one. I've got the only socket on there that really matters: the one for the shifter.

I'll probably be able to hit the power button this weekend if I can find enough jumpers! Albeit without the luxury of a floppy drive. That connector's still in the mail.

smonson-h4-3.jpg (542.22 KiB) Viewed 5308 times

[exxos]

It's so close, I can smell it. It smells like... burning PVC.

I have RAM and I've burned TOS into the second half of the EPROM (I hope that's what the jumper near the ROM socket does).

yep

I seem to have lost my optocoupler but it's on the manifest so it's gotta be somewhere in the garage, perhaps on the floor???

Just don't use the original opto, it doesn't work

I'll probably be able to hit the power button this weekend if I can find enough jumpers! Albeit without the luxury of a floppy drive. That connector's still in the mail.

[PhilC]

Pop a serial socket on it maybe?