I installed 512K RAM internally in my msx2 Hb-F9s, works...

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By RetroTechie

Paragon (1563)

RetroTechie's picture

06-08-2010, 17:10

Yeah that should be fine, as long as you get it in DIP housing and not some SMD variety...

By Dhampird

Hero (589)

Dhampird's picture

23-08-2010, 18:38

Hello, finally i tried the install with SRAM AS6C4008 (Static 512K x8 SRAM), in the image below you will see the the diagram that I have followed, i have problems with the X5 circuit, it seems that my hb-f9s hardware has some differences with the pattern of original Hb-F9s service manual, if i install the X5 circuit like the image below i get black screen on boot, if i do the older X5 circuit using the NPN and diode, sometimes i get 256K and sometimes 512K. After this i I followed the advice of Retrotechie told me:

"You could disconnect MA18/KBDIR (S1985 pin 3) -> SRAM (pin 1?), and wire *that* SRAM pin to either GND or +5V. Doesn't matter which, as long as it's a fixed logic level. Then you have 256K always, which should work reliable. Read: so that you can run mapper test programs etc. to make sure the SRAM works okay. And/or run Z80 at some higher speeds"

I desoldered the s1985 78pin to diode and all the IC22 wires, then i desoldered S1985 pin 3 and I reconected the SRAM pin 1 to Ground, the msx boot up with 256K all the times, i passed testram and no problems with 256K, seems to work right, also with some games. Seems that works great, only with 256K. Always shown in boot 256K.

img833.imageshack.us/img833/7509/staticraminstall.jpg

After this process, I have been investigating what differences there are with respect to my hardware and service manual, for now i could find some:

img840.imageshack.us/img840/8780/picture1l.jpg

img821.imageshack.us/img821/7507/picture2dr.jpg

img715.imageshack.us/img715/5456/picture3gg.jpg

img835.imageshack.us/img835/9831/picturediagram.jpg

It seems that the important difference is the pin 9 IC22 that goes to pin 97 s1985, i wonder if i could remove this paralell cable to let pin 9 IC22 dont conected to pin 97 s1985.
Also tell that the R77 and C60 components near the IC22 are not installed.
In picture 2 you could see like a cutted track problem was fixed for someone, i think so.

I´m trying to search more diferences respect original service manual.

Thanks.

By Dhampird

Hero (589)

Dhampird's picture

24-08-2010, 02:21

Hello, I managed to make something work, i did:

-I desoldered the parallel cable showned in picture 1 and 2, the red-black parallel, i removed only from point that conects this cable with the pin 9 IC22, ( in this test i have the SRAM pin 1 to GND= 256K), it seems that with this test the msx boot ok, without problems, then i removed all the cable and i conected a jumpwire instead the cable, where the red and black cables joins to yellow points in the Picture 2. Ok, the msx works without problems.

-Then i installed the new X5 circuit:
Pin 75 S1985 to Diode --> to Pin 8 IC22
Joined pins 9 and 10 in IC22
2nf Capacitor in pin 8 and GND
and resolder again SRAM pin1 to pin3 in S1985

After the install when i booted up i get 512K on boot, but after the boot when the msx goes to Basic, a rare scroll moves on, you understand this if you see below video, happen the same if the keyboard is not conected to the motherboard, seems like a bucle error. After that i desoldered the 2nf Capacitor and i saw for one time in boot 265K, after this always shows up 512K, but the "bucle in basic problem" persists.

I remembered having this same problem when trying to replace (in the old X5 circuit diode and NPN) NPN 2N2219A for one NPN BS170, same "bucle" problem happened, at that time i resoldered again the 2N2219A.

Youtube video with related problem:

www.youtube.com/watch?v=FSrSYt26fuQ

Thanks.

By RetroTechie

Paragon (1563)

RetroTechie's picture

24-08-2010, 08:46

Video shows characters in BASIC welcome screen being deleted (as if DEL key were pressed).

And... /X5 is a keyboard return signal. Don't know this particular issue you describe, but looks like the add-on circuitry continues to do something with /X5 input after reset signal has become inactive (=when add-on circuitry should leave /X5 line alone, so that it carries keyboard signals & nothing else).

By Dhampird

Hero (589)

Dhampird's picture

24-08-2010, 20:40

Hello, I think I found a possible solution using the old NPN method, mantain pin 9 and pin 10 from IC22 joined, B signal from NPN leading directly to pin 8 iC22, you could see that in yellow in the next picture:

img840.imageshack.us/img840/6864/solution.jpg

After doing this i tried some test, with games, carts, testram, etc. Now I always see in boot 512K, for the moment I have never seen 256K, I reset many times, and tested games, changing cartridges. For now always shows up in boot 512K.

By Dhampird

Hero (589)

Dhampird's picture

25-08-2010, 23:01

Ok, it seems that circuit above works without problems, i tried a lot of times and never seen 256K again, always the 512K show up in boot and fully working tested with Testram, anyways i remembered that a friendly user of the forum "NYYRIKKI" that adapted to me the HB-F9s roms to Msx2+ told me time ago a way to make a RAM test in BASIC, is this:

a.imageshack.us/img682/8233/poket.jpg

"If the mapper is working correctly you should see all numbers running from 224 to 255 and this should repeat 8 times... It there is any other result then there is something wrong with the mapper... Please run also this test few times... This should detect if the problem is in the page selection it self rather than actual reading or writing the RAM. This is pretty close same process as the boot program does..."

Ok, i did this test when i had problems with the first PseudoStatic 512K, and i get 256K and 516K, the problem is that this test seems working like expains above, but i cant see if the result repeats 8 times because the result screen goes so fast. I wonder if it will be a way in basic to pause the result comand in screen like as when we do it in MsxDos 2 with the DIR command:

dir /p

Anyways, if there is any ways to make more RAM test would be perfect to know about them.

NOTE: about the above diagram tell that the paralell cable showed in the previous pictures was desoldered from that blue point and then from pin 97 in S1985, when i removed only that i did was reinstall a Bridge between the pins in yellow where the black and red cable was joined (you´ll see that point in previous Picture 2), that paralell cable conected to the mainboard conected s1985 pin 97 directly to pin 9 in IC22, that is the issue by which the ram was not working properly?

I want to thank:

"A lot of thanks to RetroTechie for spend his time helping me with this RAM project, practically without his help I could not have done much, or finished the project. Thanks again"

Regards.

By lovemsx

Resident (41)

lovemsx's picture

20-12-2010, 12:14

Hello people, I want to know how can I put on my X5 hb-f1, turn the pin 78 of the s1985 through a diode, and then where can I call? Hugs

By Dhampird

Hero (589)

Dhampird's picture

06-10-2011, 05:00

Hello everyone again, it's been a while since my last post here because the problem with the X5 in my HB-F9s had been solved, but now, will be great if anyone with more skills than me could compare the two diagrams that i post below. First of all tell that the above full colour diagram, at the beggining in this post, is not much clear to understand, very confuse. I followed tracks in my HB-F9s to try clarify my actual X5 install, result:

img696.imageshack.us/img696/6035/actualx5hf9sinstall.jpg

And now, i found, in this link: http://www.basshp.msxall.com/HBF9S.html ,how build a X5 circuit for HB-F9s, it is different than my actual install diagram 1, i couldnt try this for now:

img716.imageshack.us/img716/4325/differentx5version.jpg

Then, be great if anyone could explain me differences between both diagrams, or maybe search a way to try simplify diagram1. Like i said diagram1 works ok for me, but i dont know if method that i used for my install, is perfectly correct or not.

By Dhampird

Hero (589)

Dhampird's picture

11-10-2011, 01:02

Any ideas?

By bch

Supporter (3)

bch's picture

30-09-2015, 16:41

Just refloating this thread to say thanks! I've suscessfully expanded my F9S to 512k. Im using a KM684000 ram chip plugged directly on the IC13 placement (with a socket) and wireing the missing signals. The x5 circuit is like the one posted right above. It works quite well. Thanks again!

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