SuperQBoard Affecting Display

[RWAP]

This has now been verified successfully on two different TVs.

Whilst the output from a QL with the SuperQBoard attached is fine on a colour microvetic monitor, on a TV, there are white flecks across the screen (in a diagonal pattern). Remove the SuperQBoard and the display from the QL on its own is rock steady.

So, does anyone have any idea what on the SuperQBoard may be causing this affect?

[XorA]

EM interference that the QL is famous for?

[RWAP]

But surely the SuperQBoard was not originally sold causing this issue?

I am sure Dave would have some ideas, but won't be holding my breath

[XorA]

Is this an analogue or digital TV. The digital ones tend to exaggerate interference.

[RWAP]

Both tests were on an analogue TV so not to do with that...

[tofro]

Rich,

when you mention TV - Does that imply the Modulator output? No wonder if that's worse than the Microvitec

Tobias

[XorA]

Does the video circuitry use the 9V inside the QL directly? Possible a failing 7805 on the SuperQBoard would inject noise on that line!

[tofro]

Possible a failing 7805 on the SuperQBoard would inject noise on that line!

The SQBs were known to have 7805s always close to failing because of the high current they usually draw from the 9V line.

Replacing the SQB's 7805 with a switching regulator could be a solution.

Tobias

[RWAP]

Yes, the TV output was via the modulator, but as I say, RGB output to Microvetic and TV output without the SuperQBoard are fine.

It looks as though it would be worth replacing the 7805 and see if that fixes the issue

[Dave]

This symptom on SQBs is usually the 7805, or the power supply capacitors on the SQB have dried out. Either refresh them, or remove the caps and replace the 7805 with a switching regulator.