Super turbo PCB layout

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By SkalTura

Champion (328)

SkalTura's picture

24-04-2021, 15:30

Forgot one...

By Alexey

Guardian (3163)

Alexey's picture

24-04-2021, 17:59

Mounting the board on top of Z80 with thermal-conductive glue is a better idea IMO.

On this board the pins are soldered directly to Z80's pins and this board takes just a little more vertical space above Z80. Good for mounting in tight places.

By jltursan

Prophet (2534)

jltursan's picture

24-04-2021, 18:33

The bottom version somewhat neater as you don't need to directly solver over the Z80; but of course, it's taller and needs a socketed Z80. The top version fits better when there's small spaces and can be piggybacked over every Z80 outthere. How much pins you need to solder over the Z80?

And talking about this boards, how many flying wires have and how they are mounted/configured?, I've no idea about them; but I remember how many problems they have with the slots clock and music pitch...

By Alexey

Guardian (3163)

Alexey's picture

24-04-2021, 19:05

You need to solder only 4 pins to Z80. The pads near the diodes need to be soldered to devices that need the clock to slow down (disk controller, for example). Bas has more info about this board.

By Pentarou

Champion (389)

Pentarou's picture

24-04-2021, 19:21

Since the original Z80 is going to be replaced anyway, why didn't someone put an SMD version directly into the PCB instead of a socket for a DIP Z80?
And if it's just 4~5 pins to solder it's not worth do do a board like that: Keeping it small (under a square inch) would allow to order a 2 layer PCB from OSHpark for 4~5 Eur/3Pieces INCLUDING shipping.

By SkalTura

Champion (328)

SkalTura's picture

25-04-2021, 07:20

Pentarou wrote:

Since the original Z80 is going to be replaced anyway, why didn't someone put an SMD version directly into the PCB instead of a socket for a DIP Z80?
And if it's just 4~5 pins to solder it's not worth do do a board like that: Keeping it small (under a square inch) would allow to order a 2 layer PCB from OSHpark for 4~5 Eur/3Pieces INCLUDING shipping.

An SMD version of the Z80 would be possible too, but that would make the design of the board even more difficult to get all the Z80 pins to line up with the original DIP40 layout of the MSX PCB...

And a board under a square inch would be very difficult to make, since all the parts toghether are probably already pushing the limit of that size, and then you would still need to add the traces, so that would quickly become a multi layer board.

By SkalTura

Champion (328)

SkalTura's picture

25-04-2021, 07:28

Alexey wrote:

Mounting the board on top of Z80 with thermal-conductive glue is a better idea IMO.
On this board the pins are soldered directly to Z80's pins and this board takes just a little more vertical space above Z80. Good for mounting in tight places.

This board from RepairBas uses the (obsolete?) Z8581 clock generator.
Much less components than the board using the 74HC components...

By S0urceror

Master (176)

S0urceror's picture

25-04-2021, 17:20

Nice PCB. You can remove one of the XTALs. Because that is the existing clock of the MSX. Or do you do 3,58 / 7 and 10 MHz?

By Pentarou

Champion (389)

Pentarou's picture

25-04-2021, 18:38

SkalTura wrote:

An SMD version of the Z80 would be possible too, but that would make the design of the board even more difficult to get all the Z80 pins to line up with the original DIP40 layout of the MSX PCB...

AFAIK the 2 commonly available SMD versions of the Z80 (SOP & QFP) have an 1/1 relationship (same pin#/function) with the DIP pinout, very easy to adapt.

Quote:

And a board under a square inch would be very difficult to make, since all the parts toghether are probably already pushing the limit of that size

Current board seems it would already fit just right, if you remove the 40 pin sockets/pin stripes and group things a bit.

Quote:

Much less components than the board using the 74HC components...

There's a 3rd version, it condenses the TTL ICs in just one GAL/PAL.
Just one chip and it also can (could) provide software enable/disable.

Finally IMHO, I think people who are looking to have this board manufactured would prefer the Eagle/KiCad files instead of the printouts.

By jltursan

Prophet (2534)

jltursan's picture

25-04-2021, 20:36

GALs are getting harder and harder to find good ones, at least the through-hole models. Some 74HCT SMD components are far easier to buy.

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