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

[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]

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]

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!!




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