Disk ][ Card Problem

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Disk ][ Card Problem

Hello everybody.

Could someone please help me and give some hints ?

After years of unuse I am now restoring an old APPLE ][ plus, RFI Revision "D".  When I put in the DISK ][ Interface (650-X104-) it works, but I see some vertical lines on the screen. Have a look at the foto please. These lines become darker if the drive motor spins and are colmpletely gone if I pull out the interface.

I had to replace a few RAM chips (4116) and one ROM was gone but now, ROM, RAM and PROMS on the DISK interface all test good.

 

Where should I start with ? Probably  there is a component which is more suspect than the others.

Thanks in advance

 

 

 

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Oh! I though this was normal

Mine does similar interference patterns when the FDD is running. I figured it was just normal interference.

I'll watch this with interest.

 

Chesh

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Different versions of the ][/

Different versions of the ][/][+ motherboard (pre/port-RFI) and cases (aluminum back plates, etc) will have different interference patterns like that.  It can also matter what floppy drive cable is used.  The early non-shielded "rainbow" cables may be more prone to it than the later grey cables.  And the grey cables, it depends on how the shielding is grounded.  And another thing is the composite video cable itself.  Some are better shielded than others.

 

But yeah, it is fairly normal.

 

 

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softwarejanitor wrote
softwarejanitor wrote:

Different versions of the ][/][+ motherboard (pre/port-RFI) and cases (aluminum back plates, etc) will have different interference patterns like that.  It can also matter what floppy drive cable is used.  The early non-shielded "rainbow" cables may be more prone to it than the later grey cables.  And the grey cables, it depends on how the shielding is grounded.  And another thing is the composite video cable itself.  Some are better shielded than others.

Many later disk drives had a ferrite ring on the ribbon cable.  The cable made one loop through the ferrite donut.   Sometimes it was inside the drive, sometimes outside.  

This can stop RF interference between the drive motor and the computer. If you can wrangle two loops through the ferrite ring this will increase its ability to block any RF interference.

Also, you can experiment with grounding between the disk drive and the Apple - attaching an alligator clip from the computer's ground (the shell of the video connector is a convenient place) and the housing of the disk drive - a screw or some other metal point.

Or moving the drive away from either the computer or the monitor (not always easy), and also ensuring a good stable power supply (especially the +12 Volt circuit which powers the drive's motor) with good grounding.

 

 

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baldrick wrote
baldrick wrote:
softwarejanitor wrote:

Different versions of the ][/][+ motherboard (pre/port-RFI) and cases (aluminum back plates, etc) will have different interference patterns like that.  It can also matter what floppy drive cable is used.  The early non-shielded "rainbow" cables may be more prone to it than the later grey cables.  And the grey cables, it depe

All good suggestions on ways to reduce interference.

 

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Turning down the monitor

Turning down the monitor brightness can also help! :)

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jeffmazur wrote:Turning down
jeffmazur wrote:

Turning down the monitor brightness can also help! :)

 

Yeah, I noticed even back in the day that most people turned the brightness and contrast adjustments too much.

 

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Its

Good to hear that.

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Yes

That will defenitely help ... :-D

 

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