7800 needs to pre-heat!

[foxbox]

Hi guys,

 

First post on here, hoping for some expert advice as I'm baffled by an issue with a 7800 I've picked up recently.

 

When I first turn it on, the picture is really fuzzy and jumps around on the screen, if I go away and leave it for 15 minutes though it seems to work fine.

 

Had a look under the hood and it looks like there's possibly a bit of solder missing on the AV out connection, sometimes wiggling that a bit works but only after the 15 mins has passed.

 

Is this something anyone comes across before?

[+SmittyB]

I've had the opposite situation where the picture was good to start before turning fuzzy until eventually it lost colour and then became unviewable. In my case it was because as the 7800 was warming up the video frequency was drifting just enough to ruin the picture.

In my case the solution was to check the frequency it was tuned to cold, check again when it was warm, and then tune it to something in the middle where it was visible in both states.

[+DrVenkman]

Very first thing to do in these situations is check the output of your power supply and voltage regulator. Be sure the PSU and the output of the VR are both solid when the system is cold and after it warms up. If those are good, then you look at the RF modulator stuff - it's possible the coil inside the RF modulator needs a small tweak, but to be honest, RF modulators are kind of an analog electronics mess - every one of them is a compromise and aging components mean that output quality will almost always vary from machine to machine as the systems age. If the problem is with the RF modulator, it's a good excuse to AV mod the system, if you ask me.

[foxbox]

On 6/25/2021 at 11:40 PM, DrVenkman said:

Very first thing to do in these situations is check the output of your power supply and voltage regulator. Be sure the PSU and the output of the VR are both solid when the system is cold and after it warms up. If those are good, then you look at the RF modulator stuff - it's possible the coil inside the RF modulator needs a small tweak, but to be honest, RF modulators are kind of an analog electronics mess - every one of them is a compromise and aging components mean that output quality will almost always vary from machine to machine as the systems age. If the problem is with the RF modulator, it's a good excuse to AV mod the system, if you ask me.

Thanks for this - I've had the same issue with a couple of different power supplies, including one which is brand new, but will check the VR and see what that's doing.

 

Take it this isn't a common issue then? ?