Re: Re: Re: D9090 back to life !

Hi, William

Thanks for this answer. In the perticular case of my D9090, both copper leafs seems to be designed to make an efficient (and also quite esthetic) shield, but they're connected to nothing. May be something was changed in past lives of my D9090 on some non essential elements (metalic spacers replaced my nylon ones, shield wires). Would you recommand me to ground those copper leafs ?

Starting from power supply point, whole elements (DOS + SASI/ST506 Controler + HDD) seems to be connected to same grounding point (remains to be confirmed by double check anyway).

@Other owners of D9060/9090 around there reading this : Do you have precision on those shields in your HDDs ? [present/absent and, if present, grounded or not ?]

Hervé

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Message du : 01/02/2014 06:48
De : "William Levak " <wlevak@SDF.ORG>
A : cbm-hackers@musoftware.de
Copie à : 
Sujet : Re: Re: D9090 back to life !


 

Rf signals are generated by various components on the boards. The 
interfering signal is not uniform. Moving the boards relative to each 
other may move the interference source far enough from the sensitive part 
of the circuit.

Also, the interfering signal is not only on the high side of the circuit, 
but also on the ground side. Connecting the grounds together may damp out 
part of the interfering signal.

The ultimate fix for interfering signals is to put a conductive shield
between the source of interference and the sensitive circuit. This is 
usually connected to ground. It could also be connected to a constant DC 
voltage, but this has other problems.



On Mon, 27 Jan 2014, hwarin@neuf.fr wrote:

> I'm eventually suspecting this also .... they are 2 big copper leafs, one under HDD's PCB, and one under DOS board ... one side of each leaf, touching the PCB is isolated, but none appears to be grounded on any point. As I also had to extend fixations of SASI board, may be did I missed something on chassis grounding for this board ... Does anyone have an idea on this perticular point ?
>
> I had the same symptoms with the other,nearly identical, ST225; may be are they more sensible ? In all cases, this does not explain why RF interference could be present in 1 position and absent when the entire system is rotated 90° clockwise
>
> Tous vos emails en 1 clic avec l'application SFR Mail sur iPhone et Android - En savoir plus.
>
>
> ========================================
>
> Message du : 27/01/2014 19:14
> De : "William Levak " 
> A : cbm-hackers@musoftware.de
> Copie à :
> Sujet : Re: D9090 back to life !
>
>
> On Mon, 27 Jan 2014, hwarin@neuf.fr wrote:
>
>> Don't ask why, it operates well only when placed on it's right side ! (seen
> from ST225 manual, it's forbiden to use it from it's back .. and it's
> the exact position choosen by commodore)
>
> If it's not the bearings or the head stepper mechanism, it could be rf
> interference between the drive controller board and the main controller
> board. I've seen some IBM drives that would only work in certain
> positions because of rf interference. Try unmounting the drive and moving
> it as far away from the rest of the unit as possible. If it works that
> way, it's rf interference.
>
> Try adding a ground strap between the two boards.
>
>
>
> wlevak@sdf.lonestar.org
> SDF Public Access UNIX System - http://sdf.lonestar.org
>
> Message was sent through the cbm-hackers mailing list
>
>

wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org


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