Re: 2465 Displays Channel Input Traces in Top Right Quadrant Only


GerryR <totalautomation1@...>
 

Jeff,
The Test 05 Fail 44, according to my manual, indicates that the "negative level too negative" and "positive level too positive." The test indicates a "Main Board Failure Detected by Auto Level Trigger on Line Source." I assume you checked all the voltages on the supply after recapping. I had an experience where someone adjusted a supply voltage not realizing that the filter cap had deteriorated and didn't check for ripple. When the new caps were installed, the voltage was way too high. It might be that someone previously made similar adjustments and once you recapped, a similar situation has occurred. Just a thought.

GerryR
KK4GER

----- Original Message -----
From: "12ax7" <jm12ax7@outlook.com>
To: <TekScopes@groups.io>
Sent: Friday, December 27, 2019 7:38 PM
Subject: [TekScopes] 2465 Displays Channel Input Traces in Top Right Quadrant Only


My Craigslist 2465 deal initially worked ok except for very blurry traces and alphanumerics. So, a re-capping and calibration project was in order. When I opened the case to look at the PSU, one of the boards had several caps that had very clearly spewed their contents. Rather than try to use caps I had on hand I felt it would was better to source the caps from someone who had done this before. It was the right decision since the process went relatively smoothly even though it took a little longer than expected.

After recapping, the alphanumerics and traces are now very clear … very happy with that.

However, I now get TEST 05 FAIL 44 on boot up. After I push A/B the test message disappears, and all the channel traces display in the top right quadrant of the screen.

What’s strange is that both the reference and delta cursors display properly, extending from the top of the screen to the bottom. The alphanumerics display clearly at the top and bottom of the screen, across the screen as expected.

In the top right quadrant I see the traces - 3 of them only. The bottom trace is a little thicker than the other 2 leading me to believe that channel 1 and channel 2 are superimposed over each other.

I can vertically move channel 3 and channel 4 within the upper right quadrant.

I can connect a test signal to channel 3 or 4 and see the "squashed" trace ... in the upper right quadrant only.

No test signals work when connected to channel 1 or channel 2.

The fan is also caput; a replacement is on order.

I know I’m going to have to re-calibrate the 2465, but want to see if calibration is the cause of the upper right quadrant display problem, or is something else amiss.

I’m scratching my head over the block diagram and schematics trying to figure out where to start and what to dive into.
Any guidance on this would be greatly appreciated.

Thanks,
Jeff

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