My Falcon went to black screen

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sety
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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 11:30 am

Can you confirm the floppy LED flashes several time fast followed by a pause without NVRAM fitted ?
Yep. That's exactly what it does.

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exxos
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Re: My Falcon went to black screen

Post by exxos » Tue Apr 28, 2020 11:40 am

sety wrote:
Tue Apr 28, 2020 11:30 am
Can you confirm the floppy LED flashes several time fast followed by a pause without NVRAM fitted ?
Yep. That's exactly what it does.
Awesome! thanks for posting a video as well I'm sure it will help people in the future!

My take on that is, the Falcon is telling us "NVRAM FAULT" . As mentioned earlier, I see that happen all the time when I forget to plug in the NVRAM :lol:

In terms of the original poster, he's not seeing that flashing happening, so I do not believe he has a NVRAM fault.. As I do not believe his machine is even getting that far.

I'm not sure about the CT60, but I think that will boot without the NVRAM fitted ?
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Re: My Falcon went to black screen

Post by exxos » Tue Apr 28, 2020 11:44 am

@christophe.griard

Am not following well this thread.. I'm not sure if your machine has a reset fault or not... Generally you should just check on the CPU RESET & HALT... press the reset switch and make sure these switch low when pressing the switch, and they will go high again a second later (and should stay high).

One thing which caught me out, was one machine I diagnose last year with a faulty Videl, the reset pin on Videl is actually shorting out the reset signal... When I lifted RESET pin on Videl, RESET on the machines started working as expected..

So it is always worth bearing in mind that the faults on machines may not necessarily be where you think they are...
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sety
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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 12:26 pm

exxos wrote:
Tue Apr 28, 2020 11:44 am
So it is always worth bearing in mind that the faults on machines may not necessarily be where you think they are...
Yeah the poor guy isn't out of the mud yet. That's the hardest part. These things are so integrated that the faults are difficult to find... The days of changing out every IC until it works are over because only two people in the world hold 99.9% of the remaining stock of custom ICs. :(

I feel sorry for the guy because he was actually using his computer when it stopped working. That's really unfair. If he were here in Aus I would repair it for free... that is, if I could get parts.

mikro
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Re: My Falcon went to black screen

Post by mikro » Tue Apr 28, 2020 1:31 pm

sety wrote:
Tue Apr 28, 2020 10:00 am
exxos wrote:
Mon Apr 27, 2020 8:30 pm
TOS404 in my Falcon will not boot without NVRAM fitted.
Well this is embarrassing... I've been telling everyone it will, but I was too lazy to remove ct60 when I tested it. I just tested mine without ct60 fitted and it won't! :oops:
Interestingly, Centurion has made a similar statement but with different outcome: http://atari-forum.com/viewtopic.php?f= ... 45#p395045

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Re: My Falcon went to black screen

Post by exxos » Tue Apr 28, 2020 1:35 pm

mikro wrote:
Tue Apr 28, 2020 1:31 pm
Interestingly, Centurion has made a similar statement but with different outcome: http://atari-forum.com/viewtopic.php?f= ... 45#p395045
:shrug:


I did try 402 as well as 404, and neither booted without NVRAM. I think others have said differently in the past as well. But knowing how unstable these machines generally are, is probably just dumb luck which ones do and do not boot without NVRAM. :shrug: But generally I would just go with the philosophy that the machine will not boot without NVRAM.
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christophe.griard
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Re: My Falcon went to black screen

Post by christophe.griard » Tue Apr 28, 2020 2:34 pm

Hello Exxos and hello Sety,

Thanks for your interest in my Falcon failure.

I did not interact during your discussion because I was on my Falcon trying to diagnose the DALLAS IC as much as my poor skills allow me.

It took me some time to find on the web the data sheet of my DALLAS IC : below is the link to it in case it can help someone in the forum/community :
https://datasheet.datasheetarchive.com/ ... 033128.pdf

I did not see anything strange for voltage measurements (I saw some strange signals on my small oscilloscope but not enough sure to say something about it): here is the Voltage I can see on the 24 pin of DALLAS IC:
Pin 1: 5V (MOT) => means Motorola bus timing => seams to be ok
Pin 2: 6mV (No function)
Pin 3: 54mV (No function)
Pin 4: 2,3V (AD0 Multiplexed Bi-Directional Address/Data bus)
Pin 5: 2,3V (AD1 Multiplexed Bi-Directional Address/Data bus)
Pin 6: 2,3V (AD2 Multiplexed Bi-Directional Address/Data bus)
Pin 7: 2,3V (AD3 Multiplexed Bi-Directional Address/Data bus)
Pin 8: 2,3V (AD4 Multiplexed Bi-Directional Address/Data bus)
Pin 9: 2,3V (AD5 Multiplexed Bi-Directional Address/Data bus)
Pin10: 2,3V (AD6 Multiplexed Bi-Directional Address/Data bus)
Pin11: 2,3V (AD7 Multiplexed Bi-Directional Address/Data bus)
Pin12: 0V (Ground) => normal
Pin13: 5V(E)
Pin14: 8mV (AS)
Pin15: 47mV (W)
Pin16: 2àmV (No Function)
Pin17: 2 mV (DS)
Pin18: 5V (reset) => normal
Pin19: 150mV (IRQ)
Pin20: 136mV (No Function)
Pin21: 6mV (No Function)
Pin22: 125mV (No Function)
Pin23: 0v (SQW)
Pin24: 5V (VCC) => normal

Concerning your question Exxos, I made a new check (I already did it during a short exchange with PhilC) and below is what I see on the expansion port for pin 17 (Reset), pin 18 (HALT) and pin 19 (Bus Error):

- Pin 17 (Reset) :
- Just after power on, I see 5V and then rapidly 0V (instead of 5V)
- when I press the reset button, I see -5v that then goes rapidly to 0V

- Pin 18: (HALT)
- just after power on, I see +5V that goes rapidly to 0V (instead of 5V)
- when I press the reset button, I see -5V that goes rapidly to 0V

- Pin 19:
- just after power on, I see 5V that goes rapidly to 0V (instead of 5V)
- when I press the reset button, no action on signal that remains at 0V

I will try to locate the right reset pin on the VIDEL chip to see if something strange can be seen : what yould I see exxos if I succed in measuring this reset pin on VIDEL IC?
For your information, I ordered some weeks ago a COMBO IC and a VIDEL IC from Best Electronics and the parcel is on its way...

Thanks again for help and advice with all these informations.
Interested in computers / computing, especialy 8 bits/16 bits/32 bits computers from Commodore and Atari.

sety
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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 2:45 pm

christophe.griard wrote:
Tue Apr 28, 2020 2:34 pm
For your information, I ordered some weeks ago a COMBO IC and a VIDEL IC from Best Electronics and the parcel is on its way...
Be careful posting that, because if he finds out you're talking to me, it'll be the last time you ever buy from BeST. :(

christophe.griard
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Re: My Falcon went to black screen

Post by christophe.griard » Tue Apr 28, 2020 2:55 pm

Ok... I was not aware that if I talk to you Sety I would not be able anymore to order some parts from Best Electronics...

I always had nice exchanges with Bradley Koda : I obviously not know him personaly but he seems to be a nice guy and has always answered rapidly to my questions for ordering some parts from him...

So I do not fully understand the fact that I would not be anymore able to order some parts from him as I only try to make a Falcon come to life again... Probably there is some history behind that but I was not involved, so I hope I will still able to get some parts from him...
Interested in computers / computing, especialy 8 bits/16 bits/32 bits computers from Commodore and Atari.

christophe.griard
Posts: 62
Joined: Tue Feb 04, 2020 8:36 pm

Re: My Falcon went to black screen

Post by christophe.griard » Tue Apr 28, 2020 3:02 pm

Update: I had a look to pin 1 (reset) of VIDEL : I measure a stable +5V...

Very tricky this failure...
Interested in computers / computing, especialy 8 bits/16 bits/32 bits computers from Commodore and Atari.

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