Is my A1200 broken or not?

[Firefly]

Ok, so I bought a used A1200 with GVP accelerator for $200 off eBay.  I plug it into a TV via RF, and I get nothing.  Black screen.  Composite on TV. Still nothing. I install the accelerator.  Still nothing.  I hook it up to a VGA monitor with an adapter.  I get a garbled screen (too high/low refresh rate?)  I unplug the harddisk, thinking it may be boot-related.  Still no dice.

The only thing that makes me think my Miggy isn't plain dead is that I get a somewhat distinguishable screen as I power off the VGA monitor.  I think the refresh rate is tooo low or something, but I have no way to tell.

Is my poor miggy dead?

Please help!

[Thomas]

Quite simple to detect: remove all expansions, hdd, accelerator etc., keep only the motherboard as it was manufactured. Then switch it on and look at the power LED. If it goes on and half a second later becomes brighter, the board is ok. If it stays dimmed, it is damaged. Check processor, Kickstart-ROM, Chip-RAM and CIA chips.

In order to connect an Amiga to a VGA monitor you need a scandoubler. You should rather get an Amiga to SCART cable and connect it to the TV this way.

Bye,
Thomas

[Ilwrath]

Naw... I don't think it's broken.  You're getting a signal on the RGB port.  (You are correct, that the Amiga's scan frequency is out of range of your monitor.  It will cause the exact problem you are describing.)  As for not getting a picture on the TV...  Probably just hooking up video wrong.  Double and triple check your connections and wires.  Make sure your running your composite out to a composite input (not an RF input) on your TV, etc...  Of course, it could be a bad composite display output on the motherboard, but those are quite rare.  

You should rather get an Amiga to SCART cable and connect it to the TV this way.

Hmm... not if he lives in North America.  ;-)  This is why it's valuable information to fill in that location field.  haha!  Anyhow, if you're in North America try a A520 RF modulator on your video port, and see if you can get a signal from that.  If you can, it might be a bad output on the motherboard.  If not, it might be a bad input on your TV.  ;-)

[Firefly]

Well, I tried Composite on a known good Composite hookup on my TV (normally has a Gamecube hooked up) and it's coming up with a black screen.

Also, this may help to give you guys a better understanding of what's going on with the RF; When I have the RF hooked up, it goes from static when the Amiga is off, to a black screen when the Amiga is on.

Is there some sort of A1200 hardware mod that requires disabling the Composite ports or something?

Also, as far as VGA goes, I thought you only needed a scandoubler for Amiga modes, and that the A1200 could do VGA resolutions as well?  Is there any way to force the A1200 into VGA mode?  Perhaps someone can provide me with a boot disk that will force the Amiga into this mode?  I believe there is a way to write Amiga disks on a PC (I remember doing this when I had my old A1200 to make a copy of Champions of Krynn)

Thanks again, Amigans, for helping a newbie out!

[Ilwrath]

Also, this may help to give you guys a better understanding of what's going on with the RF; When I have the RF hooked up, it goes from static when the Amiga is off, to a black screen when the Amiga is on.

Hmm...  So the Amiga is outputting a stable black screen on RF.  Ok...  Try this.  hook it up via RF again, and get to the black screen.  Then give it the three-key salute (CTRL-Left Amiga-Right Amiga).  This will reset the machine, and you'll get to see if any diagnostic colors go by before you end up at the black screen.

Is there some sort of A1200 hardware mod that requires disabling the Composite ports or something?

Not that I know of.  But people have done strange things to their Amigas.  It wouldn't surprise me if someone attempted some strange hack and messed it up.

Also, as far as VGA goes, I thought you only needed a scandoubler for Amiga modes, and that the A1200 could do VGA resolutions as well?

Well... Yes.*

Is there any way to force the A1200 into VGA mode?

Not without having a pre-made boot disk, or a way of getting a display up, already.

Perhaps someone can provide me with a boot disk that will force the Amiga into this mode? I believe there is a way to write Amiga disks on a PC (I remember doing this when I had my old A1200 to make a copy of Champions of Krynn)

Nope.  The PC can't write an Amiga disk.  The only way to transfer an Amiga disk is to put its disk image on a PC disk, and then read the PC disk on the Amiga, and use a program to write it back to an Amiga disk.  (Unless you have a rather rare piece of hardware for your PC called Catweasel, in which case, PM me with your e-mail address.  I'll send ya a bare boot/test disk image.).  Otherwise, I could send it, but it would be of no use.

What you really need to do is get a display on the Amiga up.  I'd still suggest the A520 TV Adaptor on your video port.  The only other alternative is finding a 15khz compatible monitor, to continue your testing.  Since you said the video port was outputting a signal, the next step is to figure out what it is showing...

Hmm....  on the bottom of the Amiga is a trapdoor bay.  Do you have a card in that expansion bay?  If so, remove it, and retest, as well.  It can be removed by sliding it left (if the front of the Amiga is pointing toward you) until it unplugs, and then it can be tilted and removed.

[HopperJF]

LOL
First things first, leave your Amiga switched on for a minute or two
A1200s take about 30 seconds before it displays the disk prompt
Until then.. you will indeed see a black screen.

[Erol]

I would remove your accelerator card... its the cause of your problem.

seeing u dont get any picture on a standard rf lead to a tv. that says it all.

make sure the accelerator card is firmly inserted in the expansion slot.. and any memory on board is inserted and correctly match.

start with the basics first.. bare A1200 if it powers on then its a hardware fault with the accelerator card.

is there any jumpers to be set on your accelerator card??

[Firefly]

Well, it looks like my only recourse at this point is to either buy a scandoubler/flickerfixer, or an A520.

Cana nyone point me in the direction of a service manual or somesuch that I could test this with?

[patrik]

@Firefly:

Have you let your A1200 be switched on for atleast a couple of minutes without harddrive and accelerator? Someone else hinted that the A1200 needs at least 30 seconds to display the boot-image which is correct and if your diskdrive is broken or not connected properly it might take much longer than 30 seconds.

Try this with the composite connected to the tv... you can also try it with the vga-monitor connected. As long as it is an older vga-monitor which doesnt go into powersave mode because of the 15kHz signal, you should atleast be able to see the purple background colour of the boot-image after a while.. even if the image is garbled.


/Patrik