Hi Jack
It's hard to remember everything but it looks like the pulley is similar to a fan belt. There are 2 screws that holding the motor and if you loosen them a little you should be able to move the motor a bit so the pulley can be removed. Then replace it with the new one and tension the motor back and tighten the set screw first and then the other. 

-----Original Message-----
From: Jack Rubin <[log in to unmask]> 
Sent: Tuesday, November 24, 2020 5:11 PM
To: HP3000 List <[log in to unmask]>; Jim Maher <[log in to unmask]>
Cc: Jack Rubin <[log in to unmask]>
Subject: Re: [EXT]: Fwd: HP 7900A drive maintenance

Jim and Gary - 

Thanks for your help. No question the drive belt has to come off - what I'm wondering is if I have to remove the pulley to drop the drive assembly and, if so, what's next in removing the lower drive assembly. Also, I'm not sure if there is anything irrevocable in removing the pulley - does re-assembly involve special fasteners or torque settings, etc. 

I've only powered on the drive long enough to open the door and I haven't let the heads load (still retained by shipping restraints). The top heads look great but I haven't looked carefully at the lower heads, though the lower up head looks OK from the top. I can also see the lower surface of the fixed disk through the inspection window and it looks good too, so I'm cautiously optimistic.

The question is what is underneath (above) the sheet aluminum shield below the bottom disc?

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