Booth Tektronix scope dead?

[Ryan Gallagher]

Anyone familiar with older analog Tektronix 2246 Scopes. (It's a 4ch unit).

The other day our booth one (my personal one) drew an error on screen, something about invalid interrupt, I didn't catch the exact error, but now when you power it up it just tells you to turn all the variable knobs all the way CW. But that doesn't seem to have any effect or get it to finish booting. Manual doesn't seem to have much of a section about possible error messages or troubleshooting.

Manual is here:
https://download.tek.com/manual/070608300web.pdf

I should probably ask in an EE or HAM forum. It was a great unit while it lasted. Might have to start trolling eBay again.

[Tony Bandiera Jr]

At the end of Section 2-2 (page 24 of the manual in the link) The "START UP" section states that there is a "keep alive" battery that affects the startup calibrations. If it is dead it will prevent it from completing the calibrations. Since you're getting the prompt to turn the knobs CW that tells me it tries to perform the calibration, but cannot store the results (since the battery is dead).

Possible solution: Open 'er up,. find the battery, replace it, and try the startup again.

Let us know if that works...

I have the later TDS 1001B that I suspect may go the same route soon, it had set in storage for a very long time. It still works, but.....

[Ryan Gallagher]

At the end of Section 2-2 (page 24 of the manual in the link) The "START UP" section states that there is a "keep alive" battery that affects the startup calibrations. If it is dead it will prevent it from completing the calibrations. Since you're getting the prompt to turn the knobs CW that tells me it tries to perform the calibration, but cannot store the results (since the battery is dead).

Possible solution: Open 'er up,. find the battery, replace it, and try the startup again.

Let us know if that works...

I have the later TDS 1001B that I suspect may go the same route soon, it had set in storage for a very long time. It still works, but.....

Thanks I'll give her a look. Haven't opened it up yet.

I've been swamped getting the summer series started with a bunch of tack-on requests. Today was Rodriguez onstage for his first double feature installment of his sub-series. He was certainly in worse shape than I, him having stayed up intentionally 36 hours to get a more immersive experience like the characters in "After Hours" and "Into The Night", he still managed his usual 20 minutes of stories, notes and anecdotes ahead of each. Just a little less quick on his feet and tendency to slur, though he seemed to enjoy it!

[Steve Guttag]

Mr. Carlson of Mr. Carlson's Lab (YouTube) showed replacing a battery in one of his Tek scopes. It's probably worth a viewing (as are most of his videos).

[Ryan Gallagher]

Some progress.

This video is a good one for getting to the battery. However mine measures 3.4v at the terminals.
https://www.youtube.com/watch?v=GbMNFwe1bPA

That doesn't mean it isn't the problem, but suspecting elsewhere initially. I suspect I need to meter and/or scope the PS rails next and check the diodes.

I got around the "Turn all variable knobs fully CW" screen after I realized that one of my chan var knobs was free-spinning past the CW detent, in fact it was never pressing hard enough to engage the detent in the pot. After cinching those up and getting into the detent it proceeded to self cal. There were all of two mentions on the internet with that phrase and tektronix in the search. Now there are 3. ;-)

It got past self cal with only a TIME error, now on subsequent boots i'm back to one of two situations, which I believe to both be displaying an error i'm seeing mentioned in other groups, or a random interrupt error.
"Invalid Interrupt from 0289:F892" is the last one I saw, If I leave it on for a while that line starts to pile up with gibberish.

IMG_6263.jpgIMG_6264.jpg

This thread seems to lead me to the right places to solve this eventually.
https://groups.io/g/TekScopes/topic/...keep/111962503

Here is a reddit thread with similar symptoms:
https://www.reddit.com/r/oscilloscop...ing_strangely/

[Mark Gulbrandsen]

I had one of these HP scopes when I used to repair Cesium and Rubidium oscillators. Great scope even today for that sort of work. But after about a year and a half, it also stopped at a point during boot up. Took me doing some posts on an HP forum to find out the issue. Anyway, we found the guy that worked at HP that wrote the code. He said the EPROMS they used only stored the code for so many years, and that once enough bits "start to fade" that they can no longer be read. And the scope stops booting. So myself and the other guy on the forum that had the same problem sent him our EPROM chips. He erased then re-wrote the code he had kept then sent them back. To end this overly long story the scopes both worked perfect. The guy lived near Denver and didn't charge either of us... I doubt your Tek uses that sort of EPROM, but one never knows.