Faint thin vertical black lines on screen 48K

[cjba100]

Dear All,

I'm successfully resurrecting my old 48K Spectrum. So far I've done a simple Video Mod, and replaced the keyboard membrane and the voltage regulator. The only slight thing left to do is sort these faint black lines on the screen. Any thoughts as to what might be causing them? And is the chirping noise/whistling noise likely to be the coil? Does that need replacing, or does it not really matter?

With many thanks,

Christopher (Worcester, UK)

[1024MAK]

Dear All,

I'm successfully resurrecting my old 48K Spectrum. So far I've done a simple Video Mod, and replaced the keyboard membrane and the voltage regulator. The only slight thing left to do is sort these faint black lines on the screen. Any thoughts as to what might be causing them? And is the chirping noise/whistling noise likely to be the coil? Does that need replacing, or does it not really matter?

With many thanks,

Christopher (Worcester, UK)

Hello and welcome Christopher

The vertical faint black lines on the screen are not unusual on a Spectrum. In most machines, they can be reduced by replacing some capacitors. Have you renewed the electrolytic capacitors yet?

The whistling noise does indeed come from the "coil". This is actually a pulse transformer and it forms part of a DC to AC to DC converter. The noise is normal. Parts of the coil vibrate, that's what you can hear, as the frequency is in the audio range. The issue 1 and 2 boards were rather loud. The later issue boards had coils that were quieter.

Which issue number is your board?

Mark

[cjba100]

It's a 3B board.

No, I haven't replaced any capacitors yet. That's the next little project I think...

Christopher

[1024MAK]

Right, well before you order new capacitors, I will remind myself about my advice on the non-electrolytically that help with the lines.

Mark

[1024MAK]

The whistling noise does indeed come from the "coil". This is actually a pulse transformer and it forms part of a DC to AC to DC converter. The noise is normal. Parts of the coil vibrate, that's what you can hear, as the frequency is in the audio range.

Explained in greater detail here.

Mark