Amiga 1200 video problems

cyberfox_it · 30 March 2011, 12:36

Hello everyone,

i've just bought an amiga 1200 on ebay...

Of course for the seller it was 'Perfect', but for me is not...
When i turn it on, i notice some thin flickering red lines on the left upper part of the boot image (that on with the disk animation).

Once on the desktop i notice strange flickering stripes over the screen, much bigger than the previous.
They're all over the screen

Tonight i'll put online some images...

Is there someone who know the reason ?
Could be some capacitator ?

s2325 · 30 March 2011, 12:46

I think it's problem with old video cable, not Amiga.

FOL · 30 March 2011, 13:31

Try RF, Composite and RGB.
See is its the same on all.

cyberfox_it · 30 March 2011, 13:38

You think is the cable ? I've tried 2 different cables...
With my a500 and a4000 all the two cables work fine...

I've not tried the rf, today when i'll get back home i'll give a try...

i've opened the amiga, it has a kickstart 3.0...

I've noticed a strange mod... Two wires between some pins of only 1 chip of the two roms...
Does anyone know what means ?

Do you know if the clock port of a 1d4 revision is compatible with the subway ?

s2325 · 30 March 2011, 13:45

Maybe it will be easier for someone if you take a photo of this mod.

cyberfox_it · 30 March 2011, 23:23

This is a photo of the mod of the 3.0 rom of my a1200...

With the same cables the display of my amiga 500 and my amiga 4000 are perfect...

FOL · 30 March 2011, 23:38

Quote:

Originally Posted by cyberfox_it

This is a photo of the mod of the 3.0 rom of my a1200...

With the same cables the display of my amiga 500 and my amiga 4000 are perfect...

Thats normal, they cocked up the rom chips and had to mod them to correct error.

I dont think its a cable issue, hence I said try all outputs.
It would help narrow down the problem.

If it works on RGB, but not on RF or Composite, then you can rule out BT101.
You really need to try all outputs first.

cyberfox_it · 31 March 2011, 09:02

The three photos are in order from left to right RF, CVBS and RGB....

The rgb is the best of all three but is not normal because there're a lot of stripes as you can see in the photo...

I've had another amiga 1200 times ago, but i don't remember that mod on the 3.0 roms...

Why should be done ?
Which errors does it correct ?

I've posted the photos of the RF CVBS and RGB output on my tv...
No one has any idea of what i can do for try to fix it ?

jaycee · 10 April 2011, 23:08

Does the noise on RGB get worse "in sympathy" with anything? For example when reading from floppy?

What kind of power supply are you using?

netagra · 10 April 2011, 23:43

Try another PSU for starters. Your RF cable looks destroyed.

jaycee · 11 April 2011, 00:05

Yes, try another PSU. The A1200 also might need to have its capacitors replaced.

Another fault I remember is that D215, an LM385 1.2v zener reference fails and produces the banding on RGB - this then causes hassle with the composite encoder.

netagra · 11 April 2011, 07:30

My A1200 has these wires as well...

cyberfox_it · 22 April 2011, 10:19

I've used an a500 power supply, the display doesn't get worse when reading from floppy...
Do you know wich capacitators could be the cause ?
How can i recognize those to replace ?

thgill · 22 April 2011, 15:10

Bad caps typically have a fishy smell to them and sometimes looks they have slightly started to bulge and possibly have ruptured. Also might be some leaked liquid around them.

Loedown · 22 April 2011, 15:34

Quote:

Originally Posted by thgill

Bad caps typically have a fishy smell to them and sometimes looks they have slightly started to bulge and possibly have ruptured. Also might be some leaked liquid around them.

I've never seen an SMT cap that was bulging and the leakage isn't always obvious, the smell of electrolyte usually is.

Not every electrolytic that shits itself starts to bulge or leak, a cap meter is about the only way to determine if it's really faulty.

rkauer · 25 April 2011, 02:11

Also the bad smell will only show when desoldering the bugger.

netagra · 25 April 2011, 10:15

Quote:

Originally Posted by rkauer

Also the bad smell will only show when desoldering the bugger.

Correct

Loedown · 25 April 2011, 10:20

Quote:

Originally Posted by rkauer

Also the bad smell will only show when desoldering the bugger.

If something has been enclosed in something for awhile it will stink as soon as you open it, most electronic equipment won't stink because it has air holes, the exception is video cameras.

30 March 2011, 12:36	#1
cyberfox_it Registered User Join Date: Jun 2009 Location: Verona/Italy Age: 51 Posts: 38	Amiga 1200 video problems Hello everyone, i've just bought an amiga 1200 on ebay... Of course for the seller it was 'Perfect', but for me is not... When i turn it on, i notice some thin flickering red lines on the left upper part of the boot image (that on with the disk animation). Once on the desktop i notice strange flickering stripes over the screen, much bigger than the previous. They're all over the screen Tonight i'll put online some images... Is there someone who know the reason ? Could be some capacitator ? Attached Thumbnails Last edited by cyberfox_it; 30 March 2011 at 23:22.

30 March 2011, 13:38	#4
cyberfox_it Registered User Join Date: Jun 2009 Location: Verona/Italy Age: 51 Posts: 38	You think is the cable ? I've tried 2 different cables... With my a500 and a4000 all the two cables work fine... I've not tried the rf, today when i'll get back home i'll give a try... i've opened the amiga, it has a kickstart 3.0... I've noticed a strange mod... Two wires between some pins of only 1 chip of the two roms... Does anyone know what means ? Do you know if the clock port of a 1d4 revision is compatible with the subway ? Last edited by TCD; 30 March 2011 at 13:51. Reason: Back-to-back posts merged. Use the edit function.

30 March 2011, 23:23	#6
cyberfox_it Registered User Join Date: Jun 2009 Location: Verona/Italy Age: 51 Posts: 38	This is a photo of the mod of the 3.0 rom of my a1200... With the same cables the display of my amiga 500 and my amiga 4000 are perfect... Attached Thumbnails Last edited by TCD; 30 March 2011 at 23:32. Reason: Back to back posts merged. Use the edit function.

31 March 2011, 09:02	#8
cyberfox_it Registered User Join Date: Jun 2009 Location: Verona/Italy Age: 51 Posts: 38	The three photos are in order from left to right RF, CVBS and RGB.... The rgb is the best of all three but is not normal because there're a lot of stripes as you can see in the photo... I've had another amiga 1200 times ago, but i don't remember that mod on the 3.0 roms... Why should be done ? Which errors does it correct ? I've posted the photos of the RF CVBS and RGB output on my tv... No one has any idea of what i can do for try to fix it ? Last edited by cyberfox_it; 01 April 2011 at 09:28.

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30 March 2011, 12:46	#2
s2325 Zone Friend Join Date: Jun 2006 Location: Gargore Age: 43 Posts: 17,789	I think it's problem with old video cable, not Amiga.

30 March 2011, 13:31	#3
FOL PSPUAE DEV Join Date: Nov 2006 Location: Wales / UK Age: 45 Posts: 5,999	Try RF, Composite and RGB. See is its the same on all.

30 March 2011, 13:45	#5
s2325 Zone Friend Join Date: Jun 2006 Location: Gargore Age: 43 Posts: 17,789	Maybe it will be easier for someone if you take a photo of this mod.

10 April 2011, 23:08	#9
jaycee Registered User Join Date: Sep 2006 Location: Norwich, UK Posts: 57	Does the noise on RGB get worse "in sympathy" with anything? For example when reading from floppy? What kind of power supply are you using?

10 April 2011, 23:43	#10
netagra Registered User Join Date: Apr 2011 Location: Athens / Greece Posts: 33	Try another PSU for starters. Your RF cable looks destroyed.

11 April 2011, 00:05	#11
jaycee Registered User Join Date: Sep 2006 Location: Norwich, UK Posts: 57	Yes, try another PSU. The A1200 also might need to have its capacitors replaced. Another fault I remember is that D215, an LM385 1.2v zener reference fails and produces the banding on RGB - this then causes hassle with the composite encoder.

11 April 2011, 07:30	#12
netagra Registered User Join Date: Apr 2011 Location: Athens / Greece Posts: 33	My A1200 has these wires as well...

22 April 2011, 10:19	#13
cyberfox_it Registered User Join Date: Jun 2009 Location: Verona/Italy Age: 51 Posts: 38	I've used an a500 power supply, the display doesn't get worse when reading from floppy... Do you know wich capacitators could be the cause ? How can i recognize those to replace ?

22 April 2011, 15:10	#14
thgill Registered User Join Date: May 2008 Location: Mason, Ohio / USA Age: 48 Posts: 391	Bad caps typically have a fishy smell to them and sometimes looks they have slightly started to bulge and possibly have ruptured. Also might be some leaked liquid around them.

25 April 2011, 02:11	#16
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	Also the bad smell will only show when desoldering the bugger.

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