My Falcon went to black screen

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exxos
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Re: My Falcon went to black screen

Post by exxos » Mon Apr 27, 2020 7:00 pm

Normally if RTC is corrupted, the drive LED will flash several times, but then stay blank for a couple of seconds, then flash several times again.. This is indicating that the Falcon is trying to boot, but when I asked about this at the start of the thread, he said this was not happening, which suggests his machine is not even trying to boot.
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christophe.griard
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Re: My Falcon went to black screen

Post by christophe.griard » Mon Apr 27, 2020 7:12 pm

Hello Frank and Exxos,

Thanks for the trick with the RTC but as reminded by Exxos, there is no led flashing after power on... And I think the machine does not start to boot...

I have updated my previous post with first measurements on the reset circuit (to make the small chip sketches more understandable)...

I am quite sure my SIM RAM is ok (99% sure). Nevertheless, I ordered one from Exxos shop to be 100% sure...
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mikro
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Re: My Falcon went to black screen

Post by mikro » Mon Apr 27, 2020 8:15 pm

christophe.griard wrote:
Mon Apr 27, 2020 6:44 pm
Another question: could you confirm that if Dallas is out of order, the Falcon would boot (with english keyboard, time been reset, etc.)?
Defect DALLAS IC can cause all sorts of crazy issues, absolutely don't trust it!

However: if you have TOS 4.04, it can boot without DALLAS nicely. TOS 4.01 and 4.02 can't. So if you have 4.04, just try to remove/replace the circuit first.

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Re: My Falcon went to black screen

Post by exxos » Mon Apr 27, 2020 8:30 pm

mikro wrote:
Mon Apr 27, 2020 8:15 pm
However: if you have TOS 4.04, it can boot without DALLAS nicely. TOS 4.01 and 4.02 can't. So if you have 4.04, just try to remove/replace the circuit first.
TOS404 in my Falcon will not boot without NVRAM fitted.
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christophe.griard
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Re: My Falcon went to black screen

Post by christophe.griard » Mon Apr 27, 2020 8:45 pm

Hello,

I tried a TOS 4.04 and as said by Exxos my Falcon does not boot...

I was wondering if I should replace DALLAS IC and see the result: I was at this stage trying to understand what going on before desolder DALLAS IC and replace it.

But if you think a defective DALLAS IC can cause a Falcon not to boot and can lead to reset signal/HALT/Bus Error to be raised (seen on the expansion port) then I have to reconsider the replacement of DALLAS IC (the motherboard has never been touched and is very clean,and therefore DALLAS IC has never been changed)...
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sety
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Re: My Falcon went to black screen

Post by sety » 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:

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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 10:07 am

Having said that, removing nvram doesn't seem to make reset get stuck low. :?

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Re: My Falcon went to black screen

Post by exxos » Tue Apr 28, 2020 10:16 am

sety wrote:
Tue Apr 28, 2020 10:07 am
Having said that, removing nvram doesn't seem to make reset get stuck low. :?
Can you confirm the floppy LED flashes several time fast followed by a pause without NVRAM fitted ?
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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 10:51 am

I'll give it a go! I've already taken it away but I'll set it up again. :)

I'll let you know in 5

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Re: My Falcon went to black screen

Post by sety » Tue Apr 28, 2020 11:15 am

Okay got it.

It pulses really fast when on. About 2 seconds on, 4 seconds off. It does this indefinitely.

https://www.youtube.com/watch?v=z6zu2y8oXhU

Ignore the fact that the pulses seem irregular, there's nothing special there. Pulses are regular. My tiny iPhone isn't fast enough to capture it as the eye would as the pulses are quite fast.

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