A2K Black Screen

[Toni Wilen]

Disconnect CPU /HLT pin temporarily. If it still goes active (low state), it is guaranteed that CPU halts because of double fault or it is broken (but it is very unlikely). Something prevents CPU from fetching ROM boot code properly.

[Pietro.tiberi]

how can I disconnect HLT pin?
please clarify...

Inviato dal mio Redmi Note 7 utilizzando Tapatalk

[Pietro.tiberi]

CPU is working because it was pulledof from a working A2000 (from a friend)

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[solarmon]

Originally Posted by Pietro.tiberi

how can I disconnect HLT pin?
please clarify...

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Without cutting any traces, the only other option is to prevent the _HLT pin (17) from making contact in the socket are:

1. Cover the pin legs with a non conductive material.
2. Bend the pin legs out to stop it from going in the socket.

Do this at your own risk!

[Pietro.tiberi]

I reseated CPU and ROM but still the same condition HLT is Low (43mV).
I'm sure that CPU and ROM chips are ok (tested on another A2K).

Any suggestion?

[Pietro.tiberi]

Originally Posted by solarmon

Without cutting any traces, the only other option is to prevent the _HLT pin (17) from making contact in the socket are:

1. Cover the pin legs with a non conductive material.
2. Bend the pin legs out to stop it from going in the socket.

Do this at your own risk!

But this is only to check if CPU is working? If this is the case it's not needed because it works.

[solarmon]

Originally Posted by Pietro.tiberi

But this is only to check if CPU is working? If this is the case it's not needed because it works.

It is to check that the CPU itself is not asserting _HLT. It could be that the CPU is detecting something else wrong and asserting _HLT. You just want to rule out whether the CPU is the one that is asserting _HLT.

[Pietro.tiberi]

Ok thanks I understand so I'll try to do this test.
In the meanwhile i checked all connections of U500 (the ROM): all Data paths to CPU are ok (connectivity check with a multimeter D( and A(), ROM PIN31 is connected to 4.94 V, and pin10 is GROUND.

PIN 12 (_ROMEN) is connected to GARY PIN 21 and it is 4.94 (so HIGH). Do you know if _ROMEN should be active LOW or HIGH?

[solarmon]

Originally Posted by Pietro.tiberi

PIN 12 (_ROMEN) is connected to GARY PIN 21 and it is 4.94 (so HIGH). Do you know if _ROMEN should be active LOW or HIGH?

If the name of a signal has a leading "/" or "_" (or sometimes, trailing) it means that it is Active Low.

[Pietro.tiberi]

ok so is this correct? _ROMEN Not Active?

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[solarmon]

With _ROMEN you should be seeing activity signals going across it - so it should not be either staying low or staying high.

[solarmon]

I forgot a third option for disabling _HLT on the CPU.

You can use another CPU socket as a piggyback and bend the pin of that instead - then you don't have to do anything physical with your CPU.

[Pietro.tiberi]

ok I'll go for a second socket

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[Pietro.tiberi]

I changed the cpu socket, repaired a broken trace and now no more vlack screen...but after changing color 3 times it remains White.
Only power anx s-video is connected....what shoul I do?
The color sequence is Dark Grey, Light Gray , white.

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[Pietro.tiberi]

It looks like a monitor issue....the white screen should indicate all test s are ok?
Am I right?

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[jolly11]

Dark Grey: The hardware test has been completed OK, and the registers are readable.
Light Grey: The software side has passed.
White: The initialisation is correct and the system is ready to boot.

in bocca al lupo pietro!

[Pietro.tiberi]

So I’ll try with another monitor via RGB...

Grazie


Inviato dal mio iPhone utilizzando Tapatalk

[jolly11]

maybe with rgb it shows some other colours in the booting test
by the way, white screen could be a cpu problem (cpu failure, broken tracks or dull cold joint or broken pads)..or maybe needs recapping

[Pietro.tiberi]

No i don’t thing so. CPU problem is black screen. I checked all track ...Recapping on A2000 should not be needed...let’s see....))


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[jolly11]

http://wiki.classicamiga.com/Amiga_b...r_code_colours

seems that black screen=no cpu detected
white screen=cpu failure

Non so però se quello che dice il sito sia affidabile al 100%