exxos's Atari, Amiga & retro forum

UniTerm is another classic ST terminal.

Pacman wrote: ↑Mon Mar 15, 2021 12:48 pm Is the VT52 terminal ACC (from the Atari language disk) the easiest terminal to use for this?

It's a perfectly workable solution, yes.

I've received the Exxos diagnostic cartridge and nullmodem-cable, and connected the faulty Mega STe to the working STe, but nothing on the terminal screen on the STe (VT-52 terminal emulator).
I don't know if I'm doing it correctly, or if the Mega STe is "too dead" for it to work. Here's what I've done:

1) diagnostic cartridge with jumpers configured for the Mega STe, plugged into the Mega STe and the correct way (jumpers, IC and other components facing upwards)

2) Exxos nullmodem cable connected between "Modem 1" (Mega STe) and "Modem" (STe). The Mega STe has 3 modem/serial ports, so I'm a little uncertain about this.

3) I have the Atari VT-52 terminal accessory (EMULATOR.ACC) running on the STe. I've never used it before, but click it once and I get two choices: (1) UNDO to return to desktop or (2) HELP to configure terminal. I assume at this stage something should come up a few seconds after powering up the Mega STe, right?
I checked the default configuration and it appears to be set correctly according to what's suggested earlier:
Baud rate: 9600
Parity: None
Duplex: Full
Bits/char: 8
Strip bit: On
Xon/Xoff: Off
Rts/Cts: Off


So is my procedure/setup correct?

Your procedure sounds fine, although I don't know about which serial port you should use on the MSTE. On the TT, the diag cart output comes out of the "primary" port that is on the motherboard. I assume you have tested the others?

Do you have another, working ST you could use to verify you do get output from that one?

I've just tested all three serial ports (they all have a 9 pin D-sub connector which fits the cable) but with no different results.
So next I reconfigured the cart jumpers for "STe", plugged it into the STe and powered up just to see if it was OK or I had used it incorrectly somehow.

Strange thing though.... the menu came up on the screen but very slowly, one letter at a time. It probably took 2 minutes for the entire menu to appear. I'm sure it's not supposed to be like that but I suspect it may have to do with: (a) the MonSTer board installed and (b) the two TOS EPROMs have been physically removed (needed for the MonSTer to work properly). The jumpers on the diagnostic cartridge were apparently correct as the title said it was for the STe (I assume the jumpers only address different diagnostic programs inside the ROM and don't do anything else?).
I don't feel like removing the MonSTer as I don't want to risk another non-working ST, and it's all working so well now.

I "only" have two STs: the working STe and malfunctioning Mega STe, so nothing else to test with. Looks like I need to do some more troubleshooting in the MSTE hardware though I'm not sure where to start.
Today I completed re-installing a SIP-header type socket so I could easier check shorts between the pins and other circuit traces/nearby vias, and also got to check possible damaged vias. All seems OK there (from and around U1), and I'm very happy with this solution compared to using a standard socket.
I've also pushed the 68000 PLCC socket pins inwards (following parts of this guide) to ensure that wasn't the cause of my problems. Still not display output or sign of life other than the spinning PSU fan and power LED.

May be the CPU is not working. The CPU PLCC Socket is bad ...

Yes, that may be a possibility although I tested the same CPU in the STe and it boots and works fine.
But as others have pointed out -when inserting/removing the MonSTer board several times this might be causing contact problems, so even though all contacts appear OK there might still be some issues...
I will use my multimeter to check for continuity from all those pins, but actually that'll only confirm contact between the PLCC socket and to the rest of the computer. There's not enough room to insert a multimeter probe to each pin of the 68000, so I guess the way to do that is to check each signal (but lacking the knowledge and a proper oscilloscope makes that hard).

But the 68000 should be a good place to start for narrowing down the problems?

A silly question perhaps, but might be worth asking.... could it be that even though my various 68000 CPUs all work in my STe but inserted into the Mega STe won't make it work that the CPU might need replacing anyway? Let me explain....

The one from my STe is marked: MC68000FN12F
I also have one: MC68000FN8
They both work in the STe, but neither makes my Mega STe boot up. So I'm wondering if the lacking 16 MHz capability might be the cause -or wouldn't that make any difference when booting up?
The Mega STe came with an MC68000FN12F with an additonal "16 MHz" marking. That one works in the STe as well, so the above statement then wouldn't make any sense unless the Mega STe uses some address lines or other parts of the CPU which is damaged and the STe doesn't use.

Could it make a difference if I buy a 68HC000 (Exxos item #0092) which I understand can handle all the way up to 32 MHz?

the MSTE boosts to 16mhz which means other cpus won't likely work. But if the CPU works in a STE then its unlikely to be damaged. Even so, the CPU in the store may help, but assume not.

Have you checked the bus resistors? In that you get 10k pull up on most CPU pins?

Mega STE boots always with 8Mhz / Cache off without the General CPX to the Desktop ...