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Old 20 March 2009, 19:18   #1
jbenam
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Hello fellow Amigans.

Here's a peculiar situation that needs a little of back-story:
Some months ago, I took my Amiga out again, in renewed interest thanks to CF cards et similia. When I went to power up my miggy with the composite output, it didn't display anything. Sadly I had lost my RGB-to-SCART cable long long ago, so I opened the Amiga up to see what was wrong. Then I noticed that almost all the capacitors had leaked. A real mess. When testing with a borrowed RGB-to-SCART cable, I noticed I had several input and serial problems. My Amiga also had problems starting sometimes, hanging on the Light Grey or the White screen. I had to reset it a lot of times for it to go, and sometimes the Keyboard led would stay on, and I couldn't use the keyboard. So I thought that changing all the capacitors was the way to go. Sadly, I had to give the RGB-to-SCART cable back, so I did almost everything of the next things without directly checking how my Miggy was after every operation.

When I started changing them, I noticed that there was a lot of electrolytic liquid under the Video Encoder (U12), so I desoldered it and cleaned it. The Composite output started to display something (even if deeply messed up) and I could almost clearly see the 2.05 Kickstart screen under it, so I guess my Amiga was still well back then. By continuing changing the capacitors, I also noticed the Reset Timer (U14) had a lot of leaking on it (and beneath it), so I thought that might have been the cause of the booting problems. After desoldering it, I cleaned it, but sadly, when resoldering it, some pads lift off (I dunno how it could've happened... probably the electrolytic acid corroding them?)... Seeing my Power LED wouldn't dim a bit on boot (it did that normally...), I thought something happened to the Reset Timer. But without a way to see the screen, I couldn't know what was really happening. Suddenly, I thought of building a RGB-to-SCART cable myself, and I finally got around to do it today morning (should've thought of it before ) and now I get a Yellow almost-Orangish screen. When I turn it off switching my PSU on OFF, the screen also turns RED for a while.

I've tried to remove the Kickstart to see if something changed, but it's the same, with or without the KS in. Also tried to do the same without the Reset Timer. The same with or without it soldered... so I guess it's that?

Now I've tried some alternate points (mainly just following the track back and soldering on it) but I can't get any results. I sadly don't know how to check voltages and things (someone got a good guide for that? ) but I guess it'd help greatly.

Also I can't really know if my self-built RGB cable really works... I followed these pinouts. I'll try to get a hang of another miggy (working) to test it. But I guess it wouldn't behave this way, if it really was a cable issue?

Now... sorry for all this long wall of text... and please, Amiga Hardware Gurus, help me

EDIT: If someone needs them, don't hesitate to request me a pic of the motherboard, I'll try my best to do a pic of the area!

Last edited by jbenam; 21 March 2009 at 21:26.
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Old 20 March 2009, 19:51   #2
JuvUK
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Hi jbenam,
don't know if these are any help to you?

You may notice that when you turn on or reset your Amiga a few different colors flash by. These actually mean something. Here you go:
Red Bad ROM
Yellow CPU Exception Before Bootstrap Code is Loaded
Green Bad Chip RAM or Agnus (check seating of Agnus)
Black No CPU
White Expansion passed
Grey CPU Passed

Constant white is failure of CPU.

Cheers, JuvUK
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Old 21 March 2009, 20:03   #3
jbenam
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Quote:
Originally Posted by JuvUK View Post
Hi jbenam,
don't know if these are any help to you?

You may notice that when you turn on or reset your Amiga a few different colors flash by. These actually mean something. Here you go:
Red Bad ROM
Yellow CPU Exception Before Bootstrap Code is Loaded
Green Bad Chip RAM or Agnus (check seating of Agnus)
Black No CPU
White Expansion passed
Grey CPU Passed

Constant white is failure of CPU.

Cheers, JuvUK
Thanks for this. I guess then it's a CPU Exception.
I don't have any clue on how to search what is causing it... Any hint?

Thanks again!
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Old 21 March 2009, 20:52   #4
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1st things 1st m8y, make sure ALL your chips are properly seated.

what we need is some Zetr0 help on this CPU exception thingy, i'll give him a call and let you know what i find out

cheers, JuvUK
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Old 21 March 2009, 21:04   #5
jbenam
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Quote:
Originally Posted by JuvUK View Post
1st things 1st m8y, make sure ALL your chips are properly seated.

what we need is some Zetr0 help on this CPU exception thingy, i'll give him a call and let you know what i find out

cheers, JuvUK
Thanks a lot... yeah, I guess we really need Zetr0 here

I'll give my miggy another look, and see if everything is properly seated.

By the way, some infos would be nice... here they are:

1) Without a Kickstart seated in, what screen colour should appear?
2) Without a Reset Timer soldered, what screen colour should appear? I guess the Reset Timer gives the miggy the reset signal.
3) Does the Amiga use the reset signal at the start of the boot sequence, or only at the end of the selfchecks?

If someone knows the answer to these three questions, I could at least rule out something

Thanks again!

Last edited by jbenam; 21 March 2009 at 21:34.
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Old 21 March 2009, 21:10   #6
JuvUK
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well the answer to the 1st one is red as in no rom or bad rom
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Old 21 March 2009, 21:11   #7
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Hi jbenam,

The link in your opening post should have appeared like this:
http://pinouts.ru/VideoCables/AmigaScart_pinout.shtml

I assume you tried to insert a pcture of the table, but it's html code - not a graphic.

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Old 21 March 2009, 21:13   #8
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do the keyboard lights flash at all?

Failed Test
Red ROM Error - Reseat or replace Green CHIP RAM error (reset AGNUS and re-test) Blue Custom Chip(s) Error Yellow 68000 detected error before software trapped it (GURU) The system performs the following test sequence:
  1. 1. Delays beginning the tests a fraction of a second to allow the hardware to stabilize.
  2. Jumps to ROM code in diagnostic card (if found)
  3. Disables and clears all DMA and interrupts.
  4. Turns on the screen.
  5. Checks the general hardware configuration.
    If the screen remains a light gray colors and the tests continue, the hardware is OK.
    If an error occurs, the system halts.
  6. Performs checksum test on ROMs.
    If the system fails the ROM test, the screen display turns red and the system halts.
Keyboard
One Blink ROM Checksum failure Two Blinks RAM test failed Three Blinks Watchdog timer failed Four Blinks A short exists between two row lines or one of the seven special keys (not implemented)
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Old 21 March 2009, 21:40   #9
jbenam
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Quote:
Originally Posted by prowler View Post
Hi jbenam,

The link in your opening post should have appeared like this:
http://pinouts.ru/VideoCables/AmigaScart_pinout.shtml

I assume you tried to insert a pcture of the table, but it's html code - not a graphic.

prowler
Yeah, I dunno how something like that could slip under my eyes Fixed, thanks


Quote:
Originally Posted by JuvUK View Post
do the keyboard lights flash at all?

Failed Test
Red ROM Error - Reseat or replace Green CHIP RAM error (reset AGNUS and re-test) Blue Custom Chip(s) Error Yellow 68000 detected error before software trapped it (GURU) The system performs the following test sequence:
  1. 1. Delays beginning the tests a fraction of a second to allow the hardware to stabilize.
  2. Jumps to ROM code in diagnostic card (if found)
  3. Disables and clears all DMA and interrupts.
  4. Turns on the screen.
  5. Checks the general hardware configuration.
    If the screen remains a light gray colors and the tests continue, the hardware is OK.
    If an error occurs, the system halts.
  6. Performs checksum test on ROMs.
    If the system fails the ROM test, the screen display turns red and the system halts.
Keyboard
One Blink ROM Checksum failure Two Blinks RAM test failed Three Blinks Watchdog timer failed Four Blinks A short exists between two row lines or one of the seven special keys (not implemented)
Well, my CAPS Lock Led stays steady all the time... no blinking

Quote:
Originally Posted by JuvUK View Post
well the answer to the 1st one is red as in no rom or bad rom
Thanks that helps...
Now here's what happened.

After pushing all the ICs, I powered it on a few times, and got a black screen. Oh well, let's turn it on and off a few times... White screen. Nice! A progress, I guess. Then I turned it off, and returning some minutes after, to see if everything was still like that. Then, when powering it up, I got a PALE YELLOW screen. I turned it off and thought of pressing some ICs a bit more. Now I get a black screen
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Old 21 March 2009, 21:55   #10
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it sounds to me like it's a CPU problem (although i've now heard of one of these going pop, i guess it's still a possability) white, yellow and black screens all seem to point to the CPU, stoopid question time, there's no sign of any greenish furry stuff on the mobo anywhere is there?
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Old 21 March 2009, 21:59   #11
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hmmm this doesn't bode well, take a look at this m8y


http://en.allexperts.com/q/Amiga-Pro...snt-show-1.htm

Cheers, JuvUK
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Old 21 March 2009, 22:21   #12
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Quote:
Originally Posted by JuvUK View Post
hmmm this doesn't bode well, take a look at this m8y
Hey JuvUK,

Who needs Zetr0 when you're around? You're even beginning to sound like him now!

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Old 21 March 2009, 22:33   #13
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Originally Posted by prowler View Post
Hey JuvUK,

Who needs Zetr0 when you're around? You're even beginning to sound like him now!

prowler
rofl, what you trying to say?
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Old 21 March 2009, 22:41   #14
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rofl, what you trying to say?
Could it be that we have found a 'Deputy Zetr0' to patrol the board in the absence of the Master?
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Old 21 March 2009, 22:45   #15
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lol nah, i am but a worm in the mighty Zetr0s presence

i've just had soooooo, much help from the "real" masters on here it's nice to try and help some one else for a change

Cheers, JuvUK
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Old 22 March 2009, 00:36   #16
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Just a tip: capacitor leakage is an acid! The first effect of the gunk is loosing the copper tracks from the motherboard, then starts to corrode the copper from the under side.

A600 don't have chips who might come loose but the ROM chip. First thing to do is wash the entire motherboard with pure water, or even use some baking soda on it to neutralize acid, then wash it again with pure water.

Let the board dry for a couple of days on direct sunlight and then start the tests again.
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Old 22 March 2009, 00:46   #17
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Originally Posted by rkauer View Post
Just a tip: capacitor leakage is an acid! The first effect of the gunk is loosing the copper tracks from the motherboard, then starts to corrode the copper from the under side.

A600 don't have chips who might come loose but the ROM chip. First thing to do is wash the entire motherboard with pure water, or even use some baking soda on it to neutralize acid, then wash it again with pure water.

Let the board dry for a couple of days on direct sunlight and then start the tests again.
Good advice, rkauer. However, it's best to use (a little) bicarbonate of soda to neutralize residual traces of acid, since baking soda contains tartaric acid as well as bicarbonate of soda.

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Old 22 March 2009, 04:31   #18
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Thanks for the translation update, Prowler! I always think baking soda was exactly "pure" bicarbonate.
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Old 22 March 2009, 04:41   #19
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Thanks for the translation update, Prowler! I always think baking soda was exactly "pure" bicarbonate.
You're welcome, mate.
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Old 22 March 2009, 19:11   #20
jbenam
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Thanks for the help, guys

I'll try to wash my motherboard and see what happens.

By the way, I powered my miggy on just a while ago, and after checking the RGB cable, I got a Green screen. Turned it off, pushed a bit the RAM, and got a Black screen again

My poor miggy

I hope the little "wash" will do her good I'll reply as soon as I get some results after drying.

Thanks again
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