White screen with STacy

Problems with your machine in general.
Roberto
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Re: White screen with STacy

Post by Roberto »


:dualthumbup: Okay, ROMs successfully written and verified working in a Stacy, with the diag cart to boot.

Will drop these in the mail to @Roberto tomorrow.
Uauuu,
Thanks Derkom! While I was reading your post higher up, where you said that you had some problems with writing the EPROMs, I was already thinking of sending you mine to be able to test them in your STacy and therefore expected another hypothesis, but since you succeeded, not I look forward to receiving them!
Roberto
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Re: White screen with STacy

Post by Roberto »

stephen_usher wrote: Sun Jul 10, 2022 12:17 pm Indeed.

The diag ROM requires that the machine can at least run the first few instructions in the ROM so that it can check for the existence of a cartridge and transfer execution to the code in the cartridge.

What equipment do you have available to you?

If you just have a multimeter this is going to be difficult, but you can check a few things, e.g. is the /HALT line on the CPU low? Are the voltages on the address and data lines sort of in the region of 3V - 4V? (If so then they're probably active. If they're 5V or 0V then they're not.)

With an oscilloscope then they are in a far better place to diagnose things.
Hi stephen_usher, unfortunately I only have a multimeter, I don't have an oscilloscope, but I am so determined to find the problem with my STacy that it will be the next step I will take; of course I will first see if with the new EPROMs that will arrive I will solve the problem. In the meantime, I can check what you advised me to do.
Roberto
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Re: White screen with STacy

Post by Roberto »

:dualthumbup: Okay, ROMs successfully written and verified working in a Stacy, with the diag cart to boot.

Will drop these in the mail to @Roberto tomorrow.
they have arrived !!!!!!!!! thanks derkom! now the question (not trivial) is this: is the HI-LOW position correct or should I exchange them?

F4AB78A2-829A-46EF-B3CA-D22A321E55F8.jpeg
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update: removing the old EPROMs I saw that below are labeled HI and LO. However (unfortunately) they don't seem to be responsible for the problem, as I still have a white screen. now I leave the stacy on for a while hoping to see which component is heating up, since the motherboard draws 1 amp!

second update: maybe I hadn't been careful before, but feeding the stacy motherboard with + 5v from an external power supply through floppy cables, it absorbs 1 ampere, while from the power supply through the jack on the back (16 V), it absorbs 0.40 amps; maybe because if the volts are less it is normal that it draws more current? However, it seems that no component heats up more than it should.
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derkom
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Re: White screen with STacy

Post by derkom »

Glad to hear the chips finally made it! Too bad they don't fix your problem, but at least you have a spare set now. Regarding HI and LO positions, the Stacy board is labelled something like ROM 0 and ROM 1, 0 being LO and 1 being HI. But you also shouldn't trust that I labelled things right. :lol: You'll do no harm in swapping the chips.

Regarding the current draw, I don't have any reason to imagine 1 amp is too high. I've never measured the current draw myself. If nothing is heating up, then there's no particular reason to suspect anything is amiss with power consumption.

However, moving forward, this is where things start to get more difficult, and also beyond my ability to direct.

You might start with the procedure under "troubleshooting a dead unit" in the 520/1040ST service manual: https://archive.org/details/atari520st1 ... 7/mode/2up

However, some of this diagnostic work requires an oscilloscope. You can do some of the procedures with a multimeter, but it's hard to produce conclusive evidence without a scope.

Maybe some others have some other advice on how to proceed?
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derkom
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Re: White screen with STacy

Post by derkom »

Oh, heh, when looking through the service manual myself, I'm reminded that serial does not work on an ST if you don't have +/- 12V. So powering 5V via the floppy power plug is fine for checking screen output, but not sufficient for looking for diag output on serial.

Have you looked for diag cart output on serial with the DC-DC PSU installed, or just with the floppy power connection? And while you're at it, have you verified that the DC-DC PSU is producing both +12 V (pin 4) and -12 V (pin 5)?
Roberto
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Re: White screen with STacy

Post by Roberto »

derkom wrote: Tue Jul 26, 2022 5:34 pm Oh, heh, when looking through the service manual myself, I'm reminded that serial does not work on an ST if you don't have +/- 12V. So powering 5V via the floppy power plug is fine for checking screen output, but not sufficient for looking for diag output on serial.

Have you looked for diag cart output on serial with the DC-DC PSU installed, or just with the floppy power connection? And while you're at it, have you verified that the DC-DC PSU is producing both +12 V (pin 4) and -12 V (pin 5)?
Hi derkom, I tried to swap the EPROMs (HI, LO with LO HI, of course always respecting the reference notch), but still white screen. So I really think the problem doesn't lie with those chips. I then measured, as per your advice, the voltage in the DC / DC module and I got this:

+ 12.25v in the pin marked with the red arrow in the photo;
-11.77v in the pin marked with the purple arrow in the photo.

I took the ground from one of the three pins marked with the black arrow.
I think the values ​​are in the norm with this difference (correct me if I'm wrong, I also post a photo of this measurement because I would not like to have the wrong pins to carry out the voltage checks),

ingrandimento.jpg
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I performed the test with the serial and the diagnostic cartridge, both using the power supply in the floppy pins, and using the DC / DC module, but in both cases I had no results in the serial data terminal.

I had already downloaded the PDF of the service manual, and I think the time has come to put into practice the procedures for identifying a dead unit.

To do this I created an extension to connect the DC / DC module (see photo), so that you can also perform measurements in the CPU, as was suggested to me by stephen_usher (I hope you are reading me right now). I would like to take those measurements you advised me to do. Currently with a multimeter, but if you give me advice on which oscilloscope to buy, that would be appreciated, as I don't have a clue which one might work for me in this case.

Thank you!!!!

IMG_6735.jpg
IMG_6735.jpg (449.53 KiB) Viewed 1130 times
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derkom
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Re: White screen with STacy

Post by derkom »

Roberto wrote: Thu Jul 28, 2022 8:04 am + 12.25v in the pin marked with the red arrow in the photo;
-11.77v in the pin marked with the purple arrow in the photo.
Those voltages are fine.
To do this I created an extension to connect the DC / DC module (see photo), so that you can also perform measurements in the CPU, as was suggested to me by stephen_usher (I hope you are reading me right now).
Be sure to check your voltages somewhere on the board after making this extension. I did the same thing for troubleshooting an ST some years ago and accidentally gave myself additional problems because my extension was dropping a volt and reducing to a point where the ST wouldn't run reliably. However my extension was poorly made with cheap components and yours looks pretty good, so I suspect you're okay.
I would like to take those measurements you advised me to do. Currently with a multimeter, but if you give me advice on which oscilloscope to buy, that would be appreciated, as I don't have a clue which one might work for me in this case.
This question I'll leave open for others to comment on, as I'm a bit clueless on scopes myself. I have an Digilent Analog Discovery 2, which does the job, but there may be better choices for you.
Roberto
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Re: White screen with STacy

Post by Roberto »

stephen_usher wrote: Sun Jul 10, 2022 12:17 pm Indeed.

The diag ROM requires that the machine can at least run the first few instructions in the ROM so that it can check for the existence of a cartridge and transfer execution to the code in the cartridge.

What equipment do you have available to you?

If you just have a multimeter this is going to be difficult, but you can check a few things, e.g. is the /HALT line on the CPU low? Are the voltages on the address and data lines sort of in the region of 3V - 4V? (If so then they're probably active. If they're 5V or 0V then they're not.)

With an oscilloscope then they are in a far better place to diagnose things.
I was finally able to dedicate myself to my STacy, and, before buying an oscilloscope (derkcom, I saw that what you have costs about 400 €, that's why I'm trying to make as many measurements as possible with the multimeter, at least until I'm forced to buy an oscilloscope), I made some measurements to the CPU and in the photo I reported the voltages detected. the motherboard, while taking the measurements, was powered with its DC / DC connected to an external color monitor (with the usual white color). I hope the scheme is clear.

D0BA113A-BF50-42D9-9962-0D7EDCF7E4EC.jpeg
D0BA113A-BF50-42D9-9962-0D7EDCF7E4EC.jpeg (487.56 KiB) Viewed 1033 times
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stephen_usher
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Re: White screen with STacy

Post by stephen_usher »

You don't need a €400 oscilloscope. Something half the price, such as this, is ideal:

https://www.amazon.co.uk/Hantek-DSO5102 ... B06XDK7C3S
Intro retro computers since before they were retro...
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Collection now with added Macs, Amigas, Suns and Acorns.
Roberto
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Re: White screen with STacy

Post by Roberto »

Hey guys! Hello Derkom! I'm here to tell you that I finally have my oscilloscope. :) I hope the summer holidays went well. I did some little experience with the oscilloscope (since I didn't have the faintest idea how to use it), and then I started following the dedicated part of the atari Service manual, where it says Troubleshotting a dead unit. I connected the ground of the oscilloscope clamp to a ground point of the STacy board, and the test lead to pin 15 (clock), and I get this figure:

6C21AE7A-6951-4C09-AD62-4A06EE6091F2.jpeg
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I then opened my Atari 520ST and did the same thing, and I get this figure:

954CA50B-61F5-47BF-ABA9-6ACFC5A63408.jpeg
954CA50B-61F5-47BF-ABA9-6ACFC5A63408.jpeg (171.76 KiB) Viewed 796 times

I also checked pin 17 of 68000 and I get the same signal for both of them:

37103264-AA91-41EC-B642-59ED4582158C.jpeg
37103264-AA91-41EC-B642-59ED4582158C.jpeg (180.38 KiB) Viewed 796 times

any advice on which measurement to take is now valuable. thanks for your availability.
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