amiga 1200 screen pulsating

21 January 2013, 17:22

i am building an a1200 tower project, have got pc psu wired up and working but amiga screen pusates and writing is hazey am using a scart lead to connect to tv - is this a power problem or a motherboard problem ?
i am using a at psu with wires connected and voltages checked
+12v reading 11.54v
-12v reading -11.6v
+5v reading +4.8v
-5v reading -4.76v
shield wire not connected.
has anyone got any suggestions ?

Hewitson · 25 January 2013, 14:37

That +5v is a bit too low for my liking, but it may not be the cause of the problem. Are you able to provide a picture, or preferably a short video clip of the problem?

demolition · 25 January 2013, 15:39

If it looks like a sinosoidal pulsation, I'd think it could be a grounding problem. If it is picking up 50 Hz noise from the environment, it would be async to the 50 Hz picture being sent to the TV, thus creating a slow modulation.

I don't think it should be the PSU voltage, unless it has a lot of ripple on it.

26 January 2013, 09:53

have rechecked all connections and added a harddrive and cd rom via an ide-fix board and everything seems to be ok now, i can only assume i must have had a dodgey connection somewhere, thankyou for your suggestions.

21 January 2013, 17:22	#1
freaky-beardy Posts: n/a	amiga 1200 screen pulsating i am building an a1200 tower project, have got pc psu wired up and working but amiga screen pusates and writing is hazey am using a scart lead to connect to tv - is this a power problem or a motherboard problem ? i am using a at psu with wires connected and voltages checked +12v reading 11.54v -12v reading -11.6v +5v reading +4.8v -5v reading -4.76v shield wire not connected. has anyone got any suggestions ? Last edited by freaky-beardy; 21 January 2013 at 20:37.

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25 January 2013, 14:37	#2
Hewitson Registered User Join Date: Feb 2007 Location: Melbourne, Australia Age: 41 Posts: 3,773	That +5v is a bit too low for my liking, but it may not be the cause of the problem. Are you able to provide a picture, or preferably a short video clip of the problem?

25 January 2013, 15:39	#3
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 44 Posts: 4,190	If it looks like a sinosoidal pulsation, I'd think it could be a grounding problem. If it is picking up 50 Hz noise from the environment, it would be async to the 50 Hz picture being sent to the TV, thus creating a slow modulation. I don't think it should be the PSU voltage, unless it has a lot of ripple on it.

26 January 2013, 09:53	#4
freaky-beardy Posts: n/a	have rechecked all connections and added a harddrive and cd rom via an ide-fix board and everything seems to be ok now, i can only assume i must have had a dodgey connection somewhere, thankyou for your suggestions.

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