Amiga 4000 distorted display

Junior

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I have a A400 Rev.B with display problems , there is no diplay from the RGB when i put my monitor on this connector , but when i use the A520 Modulator i have distorted display from the RF and the video output.
The 5 volt switch supply is on pin 23 but no image with my 23pin -> scart cable , The battery is removed because this had leaking on the mobo so maybe this causes the problem ?? .


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protek

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Do you have a multimeter to measure the incoming voltage on the switching pin of the Scart plug? The voltage should be between 1,5 and 3 V. The RGB should be ok, if you're getting an image through the modulator. With monitor, you' ll need a scan doubler unless it syncs down to 15 kHz.
 

roy_bates

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AmiBayer
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on the back of the 23 port a scart cable uses the 5 volt and 12 volt rail if either of them are missing youll have no picture.

so find the pinout for the socket and get a multimeter and test if both are present on the amiga then if they are check the cble to make sure its actually feeding these to resistors in the scart plug at the other end.

you should be seeing about 12 and 3 volts at the scart plug

what monitor are you using? also...some tv's have two scart sockets and only the first one is rgb compatible.the second one might do nothing even if the voltages are there for switching.
 
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edd_jedi

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Your 'distorted display' is probably about as good as the modulator gets! Bear in mind it was designed for small 1980s CRT TVs, it will obviously look rubbish on a modern TV. I agree with the above there is likely nothing wrong with your Amiga, it will be the cable or monitor. Not all monitors like the Amiga's refresh rate, I had to try several different SCART TVs to find one that worked.
 
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Junior

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Thanks i will try to find out of the correct output are there , i have tested it with a 1084 monitor and than i have no picutre just stripes .
 

Beavis

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So it seems that there's something wrong with your sync lines, or with the 1084, but I suspect the former.
As it happens, I'm a fellow countryman, so you might consider having it fixed by me, for a reasonable fee of course.:)
 

Beavis

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Yes, sent it back today, fixed a Csync trace, a trace to the clock chip, mounted a PCB with a Li coin cell, and did a recap.
Mind you, received it last week.:LOL:
 
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