2712 SA with display (and normalization) issues #photo-notice


Ronan
 

Greetings Tekkies!

I've got a 2712 SA -- it had been sitting in storage some years (unknown time). When I plugged it in, the traces & text was shifted below the bottom of the display area. I let it run a couple hours; the trace & text eventually wandered up to and just above the top of the display area. The trace/text is sharp and bright, but the text is distorted especially near the top left and right extremes; and it varies.

Here are two images -- the normalization failure and the distorted text (which isn't always quite as bad as this example).

Distorted text: https://ibb.co/sbYzpqR
Normalization issue: https://ibb.co/ZLGTM74

I was able to get Normalization to succeed once earlier today - running complete normalization twice in succession. I then I began exploring, doing some very basic tests, after that I reset it to defaults [Util / 1 / 1] , ran the Normalization again, wherein both the Voltage and Amplitude normalization failed.

I'm reading previous posts that I should start by replacing the battery. I will pursue that and as well attempt to become familiar with the Service manual. Also I read there are some SMD-size Electrolytic I may want to check and of course power supplies.

Should any of you worked on one of these and found the same two symptoms (sometimes Normalization succeeds and other times not -- along with distorted Text and display drifting vertically after time) -- please let me know.

Thank you kindly!!

Ronan


Ronan
 

I should have added that I would like to fix this one as it has the SA option

Image of the Options/Firmware: https://ibb.co/M2vZfF5

THANK YOU!
Ronan


Ronan
 

Just one more tidbit (before I decide if I'm going to dig deep into it).

Enabling debug diagnostics and re-running the Frequency Normalization indicates this:

“ERROR in MAIN DAC OFFSET: Cannot center start spur”

Explanation: "Beginning at 10 MHz/div span, the start spur was located and
centered, then span was reduced. In 1 MHz/div span, the signal
could not be centered within 30 horizontal storage bits."

I have a “oddity”, a +30dB rise of about 70MHz width:

https://ibb.co/db150Tr 1486 MHz
https://ibb.co/5BLWK3D 1498 MHz
https://ibb.co/xh3kybp 1558MHz

Does anyone have an OCR of the 2712 Service Manual?

Thank you
Ronan


Ronan
 

just one more thing...
yeah, right. It is pretty warm in my lab in Calif. today -- I attempted a full normalization just now, it succeeded. Perhaps this is more proof I need to do the real work now from great posts such as Mike/WZ5Q, Randy/AB9GO, Marcus/PP5MS (et al).

Now I'm thoroughly convinced I need to check PS voltages/ripple, and to order two batteries -- check the caps and do the due diligence. I am headed to the copy/print store to make printouts of the 11x17 schematics.

Appears surprisingly "normal": https://ibb.co/4f3jhKW

Thanks for your virtual patience,

R


Colin Herbert
 

Have you looked here?

https://w140.com/tekwiki/wiki/2712

Not OCR, but probably useful. Failing that, try Artek Manuals (http://artekmanuals.com/). They don't have it listed but they might be able to help.

Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ronan
Sent: 18 July 2021 22:59
To: TekScopes@groups.io
Subject: Re: [TekScopes] 2712 SA with display (and normalization) issues #photo-notice

Just one more tidbit (before I decide if I'm going to dig deep into it).

Enabling debug diagnostics and re-running the Frequency Normalization indicates this:

“ERROR in MAIN DAC OFFSET: Cannot center start spur”

Explanation: "Beginning at 10 MHz/div span, the start spur was located and
centered, then span was reduced. In 1 MHz/div span, the signal
could not be centered within 30 horizontal storage bits."

I have a “oddity”, a +30dB rise of about 70MHz width:

https://ibb.co/db150Tr 1486 MHz
https://ibb.co/5BLWK3D 1498 MHz
https://ibb.co/xh3kybp 1558MHz

Does anyone have an OCR of the 2712 Service Manual?

Thank you
Ronan


 

On Mon, Jul 19, 2021 at 03:27 PM, Colin Herbert wrote:


Have you looked here?

https://w140.com/tekwiki/wiki/2712

Not OCR, but probably useful. Failing that, try Artek Manuals (
http://artekmanuals.com/ ). They don't have it listed but they might be able
to help.
OCR'ed version added.

Raymond


Ronan
 

Thank you!
Ronan