PDP-8a Restoration/RL01 issues - test-drb@ccmp.vtda.org

11 Mar 2014

...
  Date: Sun, 9 Mar 2014 09:20:00 -0700
 From: "Ian S. King" <isking at uw.edu>
 To: cctalk at classiccmp.org
 Subject: Re: cctalk Digest, Vol 127, Issue 13
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        <CAKtEJ03PodBWHzvwax32bvvzW+DQpfAJi5JevnEMiC=azEp8=g at mail.gmail.com>
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 Date: Sat, 08 Mar 2014 12:29:41 +0000
 From: anders at abc80.net
 To: cctech at classiccmp.org
 Subject: Re: PDP-8a Restoration/RL01 issues
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         <20140308122941.Horde.9d9EcJ0ZUHxRqnL8YaU7-g5 at blue.abc80.net>
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 Just a small update about what I have found so far.
 1. The "FAULT" lamp on one of the drives was broken.
 2. The solenoid on the other was jammed. This means that both drives
 behaves the same.
 3. There is no clock present from the controller.
 Have to fix the controller first.
 /Anders 
 Re: PDP-8a Restoration/RL01 issues
 Be sure you have the Berg connector on the controller oriented
 correctly.  You won't break anything if you don't, but the clock won't
 get to the drive, as you're seeing.  -- Ian
 --
 Ian S. King, MSCS ('06, Washington)
 Ph.D. Student
 The Information School
 University of Washington
 Madness takes its toll - please have exact change.

I have traced the problem back to the RL8A. The 8,2MHz oscillator is
not working. I cut the leg on the next IC after the crystal
oscillator, a 74LS00 to make sure that nothing after the integrated
oscillator was holding the clock down. I'm now waiting on a new
oscillator, unfortunately I was not able to find a though hole mounted
one, just a SMD part...
/Anders