another broken motherboard needs help :)

[pandy71]

broken HDD should have few FB those size - but IMO wire jumper can be used instead of SMD FB - null resistor should be fine to (0 ohm resistor used as jumpers)

[loth77]

Originally Posted by pandy71

broken HDD should have few FB those size - but IMO wire jumper can be used instead of SMD FB - null resistor should be fine to (0 ohm resistor used as jumpers)

uhm... sorry.... i haven't understood

[FOL]

Originally Posted by loth77

uhm... sorry.... i haven't understood

He means instead of putting a new Ferrite bead in there, short it out.

[pandy71]

sorry for my English - i never learn it formally... it is completely self learned

Yes, clean area of PCB, remove all carbon deposits - carefully - not sure how many layers is on this PCB, clean everything by decent solvent (acetone, isoprophanol), connect damaged traces by some enmalled wire or special wire for fixing PCB.

Those FB are important for EMC but IMO everything should be OK without it.

[loth77]

ahhh... now i have understood
you mean to check a broken hard disk to find that component!
right?

[FOL]

Originally Posted by loth77

ahhh... now i have understood
you mean to check a broken hard disk to find that component!
right?

Yep, .

[loth77]

and FOL, what do you think?
should i try to connect that with a simple wire without the SMD FB?

[FOL]

Originally Posted by loth77

and FOL, what do you think?
should i try to connect that with a simple wire without the SMD FB?

If you are absolutely sure there are no shorts to ground. i.e. the burnt up part, is not reading short to ground.
Just to test I would, if its all fine, then I would replace it with the intended component.

But thats just me, you have to make your own decision.

[cpiac64]

don't repair, the 12 volt aren't used in rgb scart cable

[FOL]

Originally Posted by cpiac64

don't repair, the 12 volt aren't used in rgb scart cable

Ermmm, 12v is used for Auto Switching.

[Zetr0]

the +12v is also used on some Gen Locks as well as the A520 if memory serves...

[loth77]

uhm...
so, as i have understood, that +12v is not needed to see some output on the screen, right?
this means that, if there aren't other problems, i should see the video output in the screen with a RGB cable...
but well... this doesn't happens, so i have 2 possibilities:
1) find what is wrong, repair it and keep using this motherboard as my Amiga N°1 after 17 years and 9 months.
2) keep it like this, using the composite video output and promote one of the other 2 A1200 mainboards to my Amiga N°1

i hope i can achieve the first solution

edit:
just tried again to connect with RGB
i have a white screen with one or 2 black flashes.
nothign else, then it stays white.
if it could be useful to understand the problem.

[FOL]

Originally Posted by loth77

uhm...
so, as i have understood, that +12v is not needed to see some output on the screen, right?
this means that, if there aren't other problems, i should see the video output in the screen with a RGB cable...
but well... this doesn't happens, so i have 2 possibilities:
1) find what is wrong, repair it and keep using this motherboard as my Amiga N°1 after 17 years and 9 months.
2) keep it like this, using the composite video output and promote one of the other 2 A1200 mainboards to my Amiga N°1

i hope i can achieve the first solution

edit:
just tried again to connect with RGB
i have a white screen with one or 2 black flashes.
nothign else, then it stays white.
if it could be useful to understand the problem.

Check that the scart socket your plugging it into can accept RGB.
Alot of newer TV's only accept RGB on Scart 1, When plugging into Scart 2, you get white screen as it only see's luminance connection (not the RGB).

[loth77]

In the same screen was connected the other amiga with same cable and in full colors

[Loedown]

Originally Posted by Zetr0

Hmmm looking at the pics I would say that the package type is 0805 (bigger than the 1202)

Naughty Zetr0, 1206 is the bigger package size, bah n00b

I didn't open my A500 to double check, just went off the size of the surrounding components, you can read the writing on the top and I know the Amiga didn't use 603 at that stage except in accelerators

[pandy71]

Originally Posted by loth77

just tried again to connect with RGB
i have a white screen with one or 2 black flashes.
nothign else, then it stays white.
if it could be useful to understand the problem.

Maybe something else - those burned place must be clean - carbon is conductive - it may affect other signals especially that +12V is quite high, also check other parts - especially Agnus - it is first suspect - really sensitive part that can be destroyed by surge on RGB port area.

[cpiac64]

carbon is conductive, confirm

[Zetr0]

Originally Posted by Loedown

Naughty Zetr0, 1206 is the bigger package size, bah n00b ....

hangs head in shame =(

indeed it is... I have no idea where my head was there.... its quite likely the pr0n / p0rn web-pop'ups me thinks.

[FOL]

Originally Posted by cpiac64

carbon is conductive, confirm

Indeed it is.

[pandy71]

After watching pictures i see that also FB 263 is suspected - i see something like crack on FB263, to be honest - DB23 socket need to be unsoldered, area carefully inspected under Video Port to, all PCB damages fixed, everything need to be well cleaned - unsolder, scrub, cut, wash, repair.