RX02 Difficulties

Jerry Weiss jsw at ieee.org
Fri Dec 8 18:30:12 CST 2017

On Dec 8, 2017, at 5:17 PM, Aaron Jackson <aaron at aaronsplace.co.uk> wrote:
>>> On Dec 8, 2017, at 12:53 PM, Aaron Jackson via cctalk <cctalk at classiccmp.org> wrote:
>>>> On Fri, Dec 8, 2017 at 3:03 PM, Aaron Jackson <aaron at aaronsplace.co.uk> wrote:
>>>>> Manual says it should be S1=off, S2=on for RX211 and RXV21
>>>> In the photo, I think S1 is on and S2 is off. Check them with an
>>>> ohmmeter if in doubt!
>>>> -tony
>>> Yes - you are right. I switched them back to how they were when I got
>>> the drive. I think one of the switches was half down because XXDP
>>> actually does something now.
>>> Most of the tests now look something like this:
>>> CZRXFB0 DVC FTL ERR  00034 ON UNIT 00 TST 031 SUB 000 PC: 003476
>>>      EXPECTED SECTOR=18.
>>>        TARGET SECTOR=17.
>>> I suppose these should match?
>>> Starting to think I might need to confuse myself with my logic analyzer
>>> and the RX02 control board.
>>> Thanks,
>>> Aaron.
>> To isolate the problem further, try to see if any of the errors follow
>> the media  as you move them between drives.  
>> If the same errors occur on both drives, regardless of media then the
>> RX02 system board or perhaps the Qbus controller are at fault.  
>> The field maintenance prints should allow you to trace the fault down
>> a bit further,  with or w/o a logic analyzer.
>> How many different types of errors do you see?
>> Jerry
> Thanks for the info Jerry.
> I get read errors, data errors, density errors, sector addressing
> errors. Probably every kind of error xxdp can give :)
> Please see this link if you are interested:
> https://aaronsplace.co.uk/private/o/48859c14f6a619a5316d6af37d60579c.txt
> I will take a proper look through the field manuals tomorrow, and also
> try what you suggested with trying the same media in both drives.
> Thanks,
> Aaron.

 When you have many errors it can be hard to separate the primary fault(s) from the knock-on errors.
 The M7745/M7744 or Media Errors dominate the entries.
1) Try to verify the media is a DEC 8 Inch formatted RX02 or RX01 if you do not know the source of the 
     the disks.   The disk should have only 1 hole punched for index  on the media itself.   Even if it is
     a DEC Brand, there’s still possibility that the media has been exposed to strong magnetic fields.    

     I have not seen much natural  bit-rot on my floppy media, but YMMV.   If could find someone local 
     with RX02 drives to confirm your media, that would also help rule out some things.   

      Many third party drives and controllers that were DEC compatible also had the ability to do a 
      low level format of media, something the native RX02 did not.  So if the media type is correct, but
      the format is not, they may be salvageable (with complete loss of original data).

2) Check the connections between the drives and controllers. Gently clean contacts, especially anything
    gold plated.  Getting clean signals from the floppies is critical if the RW electronics are to function.

3) Try and contrast to the other drive as previously covered.  

This will help rule out a few things and provide some better direction.


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