After a day of cleaning and lubing switches and contacts on the 576, it's not as bad as I thought. I used a small artists' brush and lightly coated a few circuit board traces with DeOxit. Using De-ox on all the controls made a big difference. I was able to go through the familiarization procedure up to #51 with optimum results.Replaced a few rusted screws and went through initial test-set up to #51 with optimum results.

Step 47 is the Step Generator.
After inserting an NPN transistor and getting a minimum step amplitude, I can't get any steps. I believe I saw some briefly yesterday, but can't get anything today. I got as far as putting my meter on step generator IC U75 pins 9,1,3,5, which respond to the "Number of Steps" switch. But have not been able to follow the path further.
I was hoping there might be someone here who knows these well enough to suggest where to suspect a problem. adapter doesn't support it, but didn't think it . I'm using an 013-069 adapter because that's what I have. Here's a short video showing the issue.
https://www.youtube.com/watch?v=FdC9qWejY2M&feature=youtu.be


Cheers,
Brent

On Thursday, August 3, 2017, 12:29:15 AM PDT, 'Craig Sawyers' c.sawyers@tech-enterprise.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Mosyt instability is due to
the Display Invert and Display Offset Zero and Cal switched being super dryed out I checked

voltages

and ripple.
Is there any easy way to get at the controls for lubrication. I have the manual, but it looks

like you strip

the knobs and pull the front off.
It looks like I'll need a lot of contract cleaner. Perhaps a larger container of De-Ox.

The push button switches are notorious on the 576 and other instruments on which they are used. I
was lucky enough to get a 576 free from a guy who worked in the BBC Technical Centre in the UK. It
had a characteristic problem with the older 576 of epoxy potting on the HT transformer (yours is a
late instrument after Tek had gone across to silicone potting, so you're OK there). The BBC were
going to put it in the skip, so this guy hauled it home intending to fix it, never got around to it
and gifted it to me.

Anyhow, to cut a long story short, this 576 had had a really nice life in a dry air conditioned
environment. But the push switches were all intermittent.

To get to one set, you have to take out all some, or all horizontal and vertical boards. You have to
take the knobs off these and undo the switch securing nuts, then a screw at the back. You have to
unplug a great number of wires (use your phone to take lots of close up photos so you can put them
back correctly). If you have the manual there are clear diagrams which show which colour wires go
where too.

Once you get them out, you will see a board with the offending switches on it. Using the flexible
nozzle on a deoxit can you get a good squirt down the inside of each switch. Exercise each one a
lot, then a final squirt. Reassemble.

Good luck - these curve tracers are well worth saving!

Craig








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Posted by: Brent Watson <brentleew2003@yahoo.com>
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