H4G - Mongrel SMT Edition

[Icky]

- 1772 and DMA Buffers

A little more SMT reworking this time the LS245 buffers on the DMA and 1772. Plus the LS06 in the top left.

Note U1 the investor fix so we don't need the DMA patch board. Also has to rotate JP18 and 19 to get better routing so GND pins are now near the bottom of the pic.

Before:

Screenshot 2020-05-28 at 22.39.23.png (838.16 KiB) Viewed 8826 times

After:

Screenshot 2020-05-28 at 22.38.47.png (833.52 KiB) Viewed 8826 times

[DoG]

Just a suggestion...

Can we do a pull up instead of a pull down on Rx on the keyboard connector so if you forget to plug it in, you don't have to hear the clicking? Drives me crazy every time I forget to connect the keyboard.

In H4 schematics it is R35 (10K ohm) tied to GND.

[exxos]

I did consider that mod, but the beeping is useful to remind the keyboard isn't plugged in. In a way it would be removing a feature

EDIT:

I guess there could be a solder jumper on the resistor for 5v or gnd though..

[DoG]

I see your point. I guess it's a nice "feature"

EDIT: A jumper would be great, or solder blob.

[Icky]

- Moving Jumpers out from underneath the PSU

We have noticed when trying to use the jumpers such as ROM Select and the SND_CS / ROM_CE ones for the SEC Booster that they are underneath the PSU when fitted. This has lead to interesting ways people have balanced or mounted their PSU.

To fix this we have moved these jumpers out from under the PSU and in the case of the SND_CS and ROM_CE have placed them near the Expansion sockets.

Before ROM Select Jumper (purple lines denote where PSU sits):

Screenshot 2020-05-29 at 14.59.05.png (856.95 KiB) Viewed 8779 times

After ROM Select Jumper:

Screenshot 2020-05-29 at 15.03.19.png (159.45 KiB) Viewed 8779 times

Before SND_CS and ROM_CE Jumpers (purple lines denote where PSU sits):

Screenshot 2020-05-29 at 16.49.13.png (594.48 KiB) Viewed 8779 times

Before SND_CS and ROM_CE Jumpers:

Screenshot 2020-05-29 at 16.47.38.png (584.04 KiB) Viewed 8779 times

[Icky]

- Resistor SILs to SMT and power pin spacing

Last components to go to SMT are the resistor SIL networks. Here is a pic of the whole board with the SMT resistor networks boxed in green. We spaced out the power pins in pink box slightly as we noticed that if using JMX connectors they wouldn't all fit in as they were too close together.

Screenshot 2020-05-31 at 10.02.39.png (837.44 KiB) Viewed 8746 times

[terriblefire]

Which RNs did you use. I've been using the CAY16 BOURN ones since my first 030 board.

[Icky]

Which RNs did you use. I've been using the CAY16 BOURN ones since my first 030 board.

@terriblefire - I based it off of the ones available at JLC but they are a similar footprint to the CAY16's according to the datasheets so those could be used.

[terriblefire]

Which RNs did you use. I've been using the CAY16 BOURN ones since my first 030 board.

@terriblefire - I based it off of the ones available at JLC but they are a similar footprint to the CAY16's according to the datasheets so those could be used.

Sounds good.

[Icky]

- What no DIL MFP

@exxos and I have been discussing removing the MFP DIL and leaving just the PLCC socket in to make things easier. This has freed up a lot of space and also made the routing easier and cleaner.

Screenshot 2020-05-31 at 19.23.10.png (449.94 KiB) Viewed 8709 times

Now that all the fixes have been done we will now look at some of the suggestions such as the Gotek HD select line via the floppy cable as per @PaulJ's suggestion and the option for keyboard pull-down to stop the beeping when a keyboard is not connected by @DoG.

Of course there will be a mammoth task of clean up once we have everything sorted out.