Switch not saving SRAM & SRAM_CLR help - {SOLVED with new SRAM chips}

Started by HIggy, June 05, 2023, 04:35:41 AM

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HIggy

Hi,

I thought I had successfully fixed an Expert 2 (fitted PicoPSU and coin cell battery for SRAM).

But when I went to setup SASI with Bootset and Switch I could not save settings.

The original SRAM showed 8mb, I only have standard 2mb. I used SRAM_CLR (CLR and CLEAR commands) and now the Command text when booting is larger!?! And I still can't save. So it looks like the SRAM has been erased.

Switch now shows 1mb and SASI driver location ED0100 is in RAM not ROM, I can't seem to install it to ROM.

Are my SRAM chips dead?

Does anyone know about the SRAMLOAD.Lzh programs? Can I write to SRAM a saved .DAT from another X68000/Emulator? SRAMSAVE.R generates a .DAT file.

I can boot and play R-Type and the computer seems fine (gfx and sound)

I've also modified Master Disk V2 with SRAM tools and Memory Test, I had to delete RESTORE.x to gain space.
It is nicer to have a setup and diagnostic disk all-in-one.

Thanks

Golga

Have you checked you have power to the Nvram(s) when powered off?

HIggy

@Golga not yet.
Looking at PCB pictures on the Internet it seems that maybe only 1 +positive pin is connected (maybe they are joined underneath on the otherside if the PCB?).
I might have soldered the + battery terminal to a non connected pin?

I think I need to take out the lower PCB and investigate.

It is strange how the text has got larger? So SRAM_CLR did do something.

I have passed all but 'Main' on memory test MTEST (text, graphics, sprite and system). I don't know how to unload module to allow this test to run.

Golga

Well it will do something when the machine is powered on because the Srams are powered by the PSU's +5.
I recently bought and repaired a Expert HD but I assume the battery is still in the same place as the Expert II.

I'm not sure how to attach pics but on mine there is a little diode next to the battery labeled D209. Get your multimeter and make sure you are getting 3 volts to and after the diode.
You should be able to access the battery withe the side removed from the machine.

HIggy

@Golga I checked battery area last night. The battery holder I fitted already had a diode!, so it went from 3V to 2.6V then down to 2.2V after motherboard diode. (I did not spot that the Expert battery is non-recharable, it was very dirty!).

I removed the battery holder diode and I am now getting 2.6V after the motherboard diode.

TIME and DATE are being saved.

Where is the SRAM? On the main side PCB?

amazin

HIggy, one of my Pros had a program on the S-RAM that I couldn't remove. The only way to be 100% sure of erasing completely the S-RAM is using the `db` command, which is the debugger that comes with the C Pro Compiler, as mentioned here:

https://gamesx.com/wiki/doku.php?id=x68000:sram_issues

See if it changes anything. For me it did the trick, I was suffering with parameters on the IPL not sticking, and this solved everything.

-Amazin


HIggy

I have just pulled out the main side PCB.
It looks really clean, I have found the 2 SRAMS.
Although I see there is also another set of SRAM 64k. On the Expert 2 the PCB is labelled SRAM but on Expert it is not:

https://eaw.app/images/X68KG_60.png

@amazin I did try that, I will try it again.
I wonder if there is more than 16K (16+64k) of SRAM on Experts do more of address need wiping?

SI.r (system information) crashes my system.

But R type plays fine??!?

I am measuring ok voltages, but might redo power connector, just need JST terminals and crimper to turn up.

HIggy

Update: I have put the PCB back in (without metal shield) and it is not booting.
If I move around my power cables the internal speaker pops like the system has just got power.

I am going to redo the lead (6pin power connector) to the PCB. Capacitor leakage had crept all along the cable and the female connector has lots of crust.

Golga

#8
I had a similar issue when I got my Expert which made me think I bought a dud. If the main board with shielding isn't locked properly into those 3 metal tabs at the back you can create a short. It's very fiddly to get the board locked in properly. For some reason I can't upload a pic so a bit hard to explain.
I only recently bought my first x68000 which turned into 3 (2 OG and 1 Expert HD). I've managed to repair all 3. I've been slowly documenting my progress on Aussie Arcade.

Edit: I just reread what you said about the leakage and installing without the shielding.


HIggy

#9
Hi,

After remaking the PSU power leads I still had the same problem, so I decided to replace the SRAM chips.
And now I can save settings to my SRAM!!

SRAM_1.jpg
SRAM_2.jpg

@Golga - thanks for info on shielding, when putting it back together I had a problem! I have left off top shielding