Piggyback RAM - TMM41464AP??

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Por bennyroger

Expert (74)

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22-09-2012, 14:32

Its been interesting to read this Colemu :-D, almost like in the old days, trial and error and usually in the end... happiness ;-)
Must look for a Sony myself just to have some fun now ;-) Oh.. I have 4 Spectravideo 738's to play with, look like junk, but they are fun projects...

Por Colemu

Hero (535)

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22-09-2012, 14:47

If I can do it, anyone can!

Been a rollercoaster, but enjoyed every minute Cool

Highly recommend the Sony HB-F1XD, excellent machine.

Still available on Fleabay too Wink

Por Colemu

Hero (535)

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22-09-2012, 18:00

Here are pictures of the top and bottom for anyone who's interested:
https://vstuff.virginmedia.com/n/50-17/uid/HUNH9V1Pu1FpDaZO/...

Por jltursan

Prophet (2542)

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22-09-2012, 18:06

Indeed, thanks for a very interesting thread!. I'll probably try myself the upgrade; so the more details about the upgrade, the better Smile

Por RetroTechie

Paragon (1563)

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22-09-2012, 20:27

Very nice you got everything working, Colemu! Smile2 Good you fixed those S1985 wires with hot glue or something. Some notes though:

  • Some isolation tape around that diode wouldn't hurt... But if I try to follow /X5 signal (pin 78), it looks like you could have picked up that signal MUCH closer to D13 / D14 (circuit trace near pin 50/51 of S1985). Or am I mistaken?
  • It looks like you connected the SRAM's /CE input to /CAS signal of a DRAM? oO

Wish I had a really simple circuit to make this MA18/KBDIR selection in any S1985-equipped MSX2. For most of these machines, there will be similar simple ways to do it. Problem is it's different for each machine... (and some actually use KBDIR)

Por Colemu

Hero (535)

Imagen del Colemu

22-09-2012, 20:49

Do I need to Move the CE mate?
Seems to work ok...

I couldn't find anthing closer to the D13/14 diodes though. Check out that manual and let me know if you find something.

I soldered the wires to the relevant S1985 PIN's then used Epoxy resin to keep everything in place. I might just use some of that on the new diode (it IS a bit exposed!) oO

I have been using the computer all day, and the only problem I came accross was that FireHawk (HD patched) will not run in MSX Music mode (on my Philips Music Module 'MSX Audio bios 1.3'), it did before. No other problems encountered... yet....

Por RetroTechie

Paragon (1563)

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22-09-2012, 20:59

The SRAM's /CE should connect to a /SLTSL signal (/SLT33 here), is that the case? If it's really tied to /CAS, you're lucky it works at all...

Por Colemu

Hero (535)

Imagen del Colemu

22-09-2012, 21:08

Well luck's been on my side mate LOL!

I'll move it, it IS connected to CAS

Looks like it needs to be on PIN 56 of S1985.

PIN 78 traces upwards on the board, not down, that was the only handy solder point I could find...

Thanks for the info (again), kept me right all the way through! Tongue

Por RetroTechie

Paragon (1563)

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22-09-2012, 21:22

/SLT33 should be on pin 2 (or possibly, use signal on pin 3/4) of IC13 (74LS32). As usual: see schematic.

Por Colemu

Hero (535)

Imagen del Colemu

22-09-2012, 22:23

Used 56 as thats where the schematic said /SLT33 was.

Maps to 3.3 but doesn't pass TestRAM

I'll check out IC13 as you suggest

PIN 2 of IC13 is the same PIN (0 ohm resistance between PIN 56 of S1985 and PIN 2 of IC13)

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