Author Topic: HP 1650B Logic Analyzer: Display issues  (Read 169 times)

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Online NivagSwerdna

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HP 1650B Logic Analyzer: Display issues
« on: April 16, 2018, 02:31:02 am »
I just bought a HP1650B on EBAY.  It's a vintage but nice device ideally suited to my needs...

.... but it has display issues. The onscreen display dialogs (black boxes) shoud have white writing in them,

Does anyone have a schematic?  Thanks in advance
 

Offline alm

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Re: HP 1650B Logic Analyzer: Display issues
« Reply #1 on: April 16, 2018, 04:07:36 am »
Don't think there is anything beyond assembly level repair information and block diagrams for all but the earliest logic analyzers. The manual does show the expected signals on the CRT connector, so that would be the obvious place to start. Looking at the picture, I would suspect the half brightness signal, apart from the usual checks like power rails. Could be something simple like a bad connection.
 
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Online NivagSwerdna

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Re: HP 1650B Logic Analyzer: Display issues
« Reply #2 on: April 16, 2018, 08:18:07 pm »
Without a schematic this is going to be challenging and I don't want to break my 'new' toy straight away... I guess I will have to imagine the text in the onscreen boxes..
... quite hard to guess with messages like... waiting for Pattern X Occurence etc  ::)

I imagine the display memory is memory mapped and clearly all that part is working correctly.

The On Screen dialog box is either hardware overlaid or software controlled... it would be nice to know which.  (I tried 2 system discs and got the same effect)
 

Online Silveruser

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Re: HP 1650B Logic Analyzer: Display issues
« Reply #3 on: April 17, 2018, 04:33:34 am »
Just out of curiosity I booted up my 1651B. The message if I just hit run the blank message says 'MACHINE 1' -- Transitions Remaining to PostStore :   127.  Scanning the System_  file with an editor lots of phrases seem to part of the software including Transitions Remaining to PostStore. 

Maybe you have corrupted file - or two.
 
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Online NivagSwerdna

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Re: HP 1650B Logic Analyzer: Display issues
« Reply #4 on: April 17, 2018, 05:00:27 am »
Took the cover off... Reseated cables, twizzled a couple of knobs but left them at the same offset I found them...

And then discovered an "intensity knob" at the back....

.. by pumping up the volume I can see text!!!!

Awesome. Thanks people!!
 
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