Various problems with A1200

[FireflyST]

Hi All,

I've decided it's time to address the other problems left on my A1200 that still plague it.  Here they are:

1. The RF output gives a black screen
2. The Composite output gives a black screen
3. The machine runs fine and is stable, but when I reboot it with ctrl-amiga-amiga, it sometimes freezes with the green LED dim and I have to turn it off for no less than 15 seconds before turning it on.  Sometimes it requires at least 5 minutes before the dim-LED problem goes away and it comes back up.

[tokyoracer]

Hi, im not expert but I will try and see if I can help.

1: Tried moving that tiny black switch next to the RF putput? I'm not totally sure what it does and what it's for but maybe woth a shot.

2: Not quite sure how to fix theis unless the outputs needs cleaning. If rusty then maybe some fine sand/glass paper would help, mind you this may be good for point 1 too.

3: Iv experianced that with my CD32, strange stuff but sorry I can't help there. Maybe a power supply problem? :-?

[rkauer]

Some hints:

RF AND composite problem? Problably U30 fried, or something around it (check the underside of the MoBo too).

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Guru on soft-reboot: did you dismount some RAM-disk before? Could be some RAM-related soft making a mess.

Download SnoopDOS, put it very soon on Startup-sequence, setted to save the log on an archive, open the archive when the Amiga comes back to live again.

If not a software-related problem, them u have to change ALL electrolytic caps on the board. They are few, unexpensive and easy to replace. Ripple on +5 rail is one of the most common cause to hardware issues.

Other thing could cause this: ur PSU. Open it and look the caps. Again: they are few and (much more) easy to change.

[meega]

The little black switch is a level adjust for the UHF, low or high output strength. Low is usually fine.

As rkauer says, if you get nothing from the composite output it means the fault is not only in the UHF modulator.

[KThunder]

meega wrote:
The little black switch is a level adjust for the UHF, low or high output strength. Low is usually fine.

As rkauer says, if you get nothing from the composite output it means the fault is not only in the UHF modulator.

black switch for ntsc is channel 3 or 4 it is different than that for pal switch is always ch36 i believe

the problem could be all the way back from the rgb source that is why rgb works but nothing else. you could use an a530 if you need composite or rf. that really sucks though because the a1200 and a530 outputs are like night and day on quality. some genlocks have composite output and look quite good.

[meega]

KThunder wrote:

black switch for ntsc is channel 3 or 4 it is different than that for pal switch is always ch36 i believe

Then that is a difference that I was not aware of, and thank you for pointing that out. :-)

There is also a small potentiometer on the UHF output of my A1200, which allows tuning of the output channel by some amount, and allows you to avoid interference with other channels received by your TV.