Just got a Mattel Aquarius, and it has issues...

[DistantStar001]

Like the title says, I just received a Mattel Aquarius but it isn't working.  Power light comes on.  It responds to the RESET button.  But all I get is a garbage screen.  

I tried reseating the only socketed IC (I think it's the ROM), and tried booting without it.  The only difference was that instead of the characters shown there were small rectangles on the screen.  However, they were in the same locations on the screen.

 

Any ideas?

[MattPilz]

When it's powered on (with volume on your TV up) press RETURN and check if you hear a BEEP and if anything visually changes on the screen. Then press CTRL + G to listen for another beep. If you at least hear the beeps, your system ROM and CPU are fine. At which point it could be bad RAM. There are two 2K RAM chips in there.

 

If you do get the beeps, you can try typing this in (blind) and press enter to see if the border changes to 'A' or any other change.

 

POKE 12288,65

 

There are two ULAs (plus a character ROM) that can go bad though I find that is rare, and unfortunately those are unobtainable beyond a donor Aquarius.

Edited April 14, 2023 by MattPilz

[DistantStar001]

32 minutes ago, MattPilz said:

When it's powered on (with volume on your TV up) press RETURN and check if you hear a BEEP and if anything visually changes on the screen. Then press CTRL + G to listen for another beep. If you at least hear the beeps, your system ROM and CPU are fine. At which point it could be bad RAM. There are two 2K RAM chips in there.

 

Sadly no beeps.  For that matter, no response at all to any keyboard input (except reset).

 

 

[DistantStar001]

I dug out my oscilloscope, and started probing the pins on the CPU.  In a nut-shell, I'm getting activity on all of the address lines, but none of the data lines.  Pin 6 has a good clock signal and there is activity on the refresh line as well.  However, the reset line is holding high immediately upon power up and stays there.  So I don't think I'm getting a reset signal.  

 

Please tell me that signal is not generated by either of the ULAs!

[MattPilz]

It has symptoms common with a corrupted system ROM. The Z80 attempts to read the RESET call on power up, from ROM, but if the ROM is ruined it may not get very far. If you hold in the RESET you'd generally see a pure black screen and that'd change to 'something' if at least that was working right.

 

Your board may have a socketed character ROM based on you saying it was all squares when you removed it, my sets always had every IC hard-soldered. Below is where the SYSTEM ROM is. Assuming it's not socketed, you'd need to desolder and add a socket to attempt swapping. It is pin-compatible with a 2716/2732/2564 EPROM and the S2 ROM is easily available (see attached).

Still wouldn't rule out a bad CPU, but would start with this system ROM.

 

aquariusS2.rom

Edited April 14, 2023 by MattPilz

[DistantStar001]

42 minutes ago, MattPilz said:

It has symptoms common with a corrupted system ROM. The Z80 attempts to read the RESET call on power up, from ROM, but if the ROM is ruined it may not get very far. If you hold in the RESET you'd generally see a pure black screen and that'd change to 'something' if at least that was working right.

 

Reset button turns the screen black, but the screen comes back exactly as before.

 

43 minutes ago, MattPilz said:

Your board may have a socketed character ROM based on you saying it was all squares when you removed it, my sets always had every IC hard-soldered.

Sadly, I was wrong.  It wasn't the ROM Socketed, but one of the RAMs.

 

45 minutes ago, MattPilz said:

Below is where the SYSTEM ROM is. Assuming it's not socketed, you'd need to desolder and add a socket to attempt swapping. It is pin-compatible with a 2716/2732/2564 EPROM and the S2 ROM is easily available (see attached).

Unfortunately, I don't have anything capable of burning E-PROMs.  Is there someplace I could acquire one pre-made?

 

47 minutes ago, MattPilz said:

Still wouldn't rule out a bad CPU, but would start with this system ROM.

Not ruling it out, but it is the part I have.  I'll start looking for the ROM first.

 

Curious.  Does the Aquarius's behavior change without its keyboard?  I'm probably grasping at straws, but I have a number of machines that can get finicky about that kind of thing.  I know the RESET key works, but I can't say the same for the rest of it.  

[DistantStar001]

IT WAS THE PROCESSOR!!!!!   

 

I would say it was a hunch.  But the truth is that I have a couple of Z80s lying around, and a 40-pin socket or two, so I figured couldn't hurt.  Also, I have no idea where to get a replacement ROM.  And I have yet to get an E-Prom burner (really need to though).  In any case, after I removed the old processor, it occurred to me that if that were the problem, then the fault screen would either resemble or be the same as what I was getting.  so I tried it without the processor and got the same screen as before.  Popped in a new Z80, and TA-DA!!!  Working Aquarius!

 

Also, to answer my last question.  No. The Aquarius's behavior does not change without its keyboard. In fact, it boots just fine.  

 

Now that it's working, I've noticed some video quirks. For instance, the initial screen pic shown is monochrome.  For some reason, my Samsung TV won't display any color with it.  It has a similar issue with Atari 8-bits and Cocos.  But usually changing the channel fixes that.  The Aquarius, on the other hand, is strictly monochrome on this screen.  I did get color on my little Sharp Aquos.  But there was intermittent, but significant graphical glitching.  Fortunately, it looks great on my old Sharp CRT TV from the '90s!  Still, has anyone else noticed their Aquarius not playing well with LCDs?