White screen with STacy

[Roberto]

Also did you countinuety check all ROM pins back to the CPU ? Do with ROM chips in place..

Hi Exxos, I was able to identify the addresses of the ROMs and what path they travel, and therefore to understand where they end up on the CPU. I have seen that they go through 17 resistances; I tested the continuity of the ROMs up to the end of the resistors and then I did the same on the other end, up to the 17 pins of the addresses on the CPU (the remaining addresses I don't know where they come from and I have not tested them since you told me to check the ROMs). everything ok I would say, do I have to proceed also for the data?

[exxos]

Yes test address and data back to the CPU.

[Roberto]

Yes test address and data back to the CPU.

perfect, I thought it would take much longer but it seems that I have taken a hand ... while the addresses are in contact with each other (i.e. the A1 pin of the ROM HI is bridged with the A1 pin of the ROM LO), then they go both to the CPU interspersed with a resistor each, the data pins are not in contact with the same data pins of the two ROMs but go into contact directly with the CPU (with no resistor in between). all addresses and data have therefore been verified and have continuity (0.00 k ohm on multimeter). as for your request to put a peak-to-peak volt limit, I couldn't do it.

I was only able to see the min and max limit of the signal voltage on the display.

3AA9DF42-EB7E-467F-81BE-2EB3EDE8F43B.jpeg (419.64 KiB) Viewed 1666 times

[exxos]

I was only able to see the min and max limit of the signal voltage on the display.
3AA9DF42-EB7E-467F-81BE-2EB3EDE8F43B.jpeg

Can also you scope the 5V from the PSU ?

Also I know you checked all chips have 5V on them.. but did you also check all the GND connections ?

Can you scope power pins directly on the CPU ?

[Roberto]

Can also you scope the 5V from the PSU ?
Also I know you checked all chips have 5V on them.. but did you also check all the GND connections ?
Can you scope power pins directly on the CPU ?

I hope I understand what you asked me to do ....

I took some time to do things calmly and well done. So for each chip I made a report; consider that I have set the multimeter to check the grounding of each chip by putting 20K Ohm as scale, so that you can also see any resistances. Direct contact (without resistance) is 0.0 K Ohm. which means the correct grounding of the pin.

As for the voltages I used my oscilloscope to measure them.

I made the check directly in the contact of the chip and not in the socket (except those with the square socket that I checked in the socket contacts since the pins of the chips are inaccessible).

I found problems in the SHADOW chip and the SHIFTER Clock (see report below).

MFP 68901:
Pin 11, Vcc + 5V (OK)
Pin 21, / RESET + 5V (OK)
Pin 35, 4 MHz (OK)
Pin 36, GND (OK)

MMU:
Pin 5, 16MHz (OK)
Pin 10, Vcc A + 5V (OK)
Pin 19, 4 MHz (OK)
Pin 20, 8 MHz (OK)
Pin 27, GND A (OK)
Pin 44, Vcc B + 5V (OK)

DMA:
Pin 20, GND (OK)
Pin 28, GND (OK)
Pin 39, 8 MHz (OK)
Pin 40, Vcc + 5V (OK)

SHADOW:
Pin 11, Vcc + 5V (OK)
Pin 12, GND (OK)
Pin 13, Vcc + 5V (OK)
Pin 21, GND (OK)
Pin 32, VCC + 5V (OK)
Pin 33, GND (OK)
Pin 35 (in the pinout of the diagram I found there is a Vcc, while in the logic diagram it says GOUT2) No voltage
Pin 45, GND (OK)
Pin 47, GND (NO !!!! Maybe a schematic error?)
Pin 53, Vcc + 5V (OK)
Pin 54, GND (OK)
Pin 55, 16MHz (OK)
Pin 66, / RESET + 5V (OK)
Pin 74, Vcc + 5V (OK)
Pin 75, GND (OK)

ACIA:
Pin 1, GND (OK)
Pin 12, Vcc + 5V (OK)

SHIFTER:
Pin 2, 32MHZ (NO !!, There is an uncertain and noisy signal of about 1 Volt)
Pin 20, GND (OK)
PIN 39, 16 MHz (OK)
Pin 40, GND (OK)

GLUE:
Pin 1, Vcc + 5V (OK)
Pin 22, / RESET + 5V (OK)
Pin 34, 8MHz (OK)
Pin 35, GND (OK)
Pin 43, 500 KHz (OK)
Pin 52, GND (OK)
Pin 54, 2MHz (OK)

MC68000:
Pin 14, Vcc + 5V (OK)
Pin 15, 8MHz (OK)
Pin 16, GND (OK)
Pin 17, / HALT + 5V (OK)
Pin 18, / RESET + 5V (OK)
Pin 49, Vcc + 5V (OK)
Pin 53, GND (OK)

2 ROM:
Pin 16, GND (OK)
Pin 1 and 32, Vcc + 5V (OK)

All minor chips have + 5V voltage and correct grounding
except U11 (I think it's the one that drives the serial interface), which has + 12Vcc. and correct grounding.

on the Hard disk connector there is + 5Vcc on the red wire and + 16Vcc on the Blue wire.
On the two Floppy Drive connectors there is only voltage on the two red wires + 5Vdc, no voltage on the two blue wires.

As for the PSU, these are the voltages (on the three GND pins there is correct grounding):

IMG_7269.jpg (324.52 KiB) Viewed 1626 times

In the PSU board there are two connectors that are in contact with the motherboard. Should I also measure the voltages of the other connector? There is no reference to the tensions (tomorrow I will try to see in the logic scheme that now I do not have here with me).

IMG_7268.jpg (373.16 KiB) Viewed 1626 times

[exxos]

I took some time to do things calmly and well done. So for each chip I made a report; consider that I have set the multimeter to check the grounding of each chip by putting 20K Ohm as scale, so that you can also see any resistances. Direct contact (without resistance) is 0.0 K Ohm. which means the correct grounding of the pin.

Thanks. All that seems correct.

Just I was also asking for you to scope the 5V and post the image on here also just to make sure that is OK. But I think you're back to removing the CPU and wiring the address bus to zero etc to see what you get as by the looks of it you should really be running.

[Roberto]

Thanks. All that seems correct.

Just I was also asking for you to scope the 5V and post the image on here also just to make sure that is OK. But I think you're back to removing the CPU and wiring the address bus to zero etc to see what you get as by the looks of it you should really be running.

Ahh ok ... I'm still waiting for that guy who looks pretty busy and I didn't get to see him this weekend. According to you, as soon as I remove the old CPU and plug in the socket, can I turn on the STacy with the new CPU? Do I risk something? Or do I check address 0 first?

[exxos]

According to you, as soon as I remove the old CPU and plug in the socket, can I turn on the STacy with the new CPU? Do I risk something? Or do I check address 0 first?

You could try placing in a new CPU once the socket is there. But as we don't know if something killed the CPU or not, then you could risk blowing a new CPU. So it's up to you if you want to do that or not.

[Badwolf]

I would genuinely do this:-

Just I was also asking for you to scope the 5V and post the image on here also just to make sure that is OK.

Before this:-

You could try placing in a new CPU once the socket is there.

Because this should be in big bold flashy letters:

But as we don't know if something killed the CPU or not, then you could risk blowing a new CPU.

'Scope the VCC lines on the 68000 itself. If it has all those sawtooth peaks and troughs we saw earlier I would be reluctant to swap it out.

BW

[Roberto]

'Scope the VCC lines on the 68000 itself. If it has all those sawtooth peaks and troughs we saw earlier I would be reluctant to swap it out.

BW

@badwolf, @exxos

in addition to struggling with the STacy card I also have to struggle with my English… yes, now I understand what @exxos was asking me. here are the photos of the two Vcc pins of the CPU. the voltage seems stable and correct.

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