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TDS-524A no trace need help

 

Dear forumers,

I need help for my TDS-524A showing no trace on any channel.
Recap and board wash performed succesfully time ago.
Self test is OK, no error in the log.
I am pretty sure it triggers properly because the "T" symbol on screen moves according to the signal.
I am thinking a video RAM chip may be defective and I replaced 2 of them without result.
There are 8 ram chips related to waveform display.

Hope someone would like to offer some hint on where to investigate.

Many thanks in advance to all of you.

Enrico
 

If the video RAM was bad, I would expect it to affect the on screen menus and graphics, not just the trace. It's odd that it passes the self test. Have you run the full self test from the test menu? Have you tried resetting the factory defaults? Does it still pass SPC?

--- In TekScopes@..., "iw0uwl" wrote:

Dear forumers,

I need help for my TDS-524A showing no trace on any channel.
Recap and board wash performed succesfully time ago.
Self test is OK, no error in the log.
I am pretty sure it triggers properly because the "T" symbol on screen moves according to the signal.
I am thinking a video RAM chip may be defective and I replaced 2 of them without result.
There are 8 ram chips related to waveform display.

Hope someone would like to offer some hint on where to investigate.

Many thanks in advance to all of you.

Enrico
 

Thanks for your message,

I will try to answer as much as I can:
-the menus and graphics have no problem
-the full self test from the menu passes ok
-SPC passes ok
-reset executes but no help
-autoset works as it set the correct values to display the probe compensation signal
-the measurement values when active are correct(i.e. frequency, voltage, etc.) so I
think the acquisition is ok.

I am troubleshooting the unit with the help of the 520 service manual which has same architecture.
As far as I understood from the description of the schematic in the manual, the text and the waveforms use separate memory planes and chips (8 bit for text and 16 bit for wfm).

Regards

--- In TekScopes@..., "baltimora86" wrote:

If the video RAM was bad, I would expect it to affect the on screen menus and graphics, not just the trace. It's odd that it passes the self test. Have you run the full self test from the test menu? Have you tried resetting the factory defaults? Does it still pass SPC?

--- In TekScopes@..., "iw0uwl" wrote:

Dear forumers,

I need help for my TDS-524A showing no trace on any channel.
Recap and board wash performed succesfully time ago.
Self test is OK, no error in the log.
I am pretty sure it triggers properly because the "T" symbol on screen moves according to the signal.
I am thinking a video RAM chip may be defective and I replaced 2 of them without result.
There are 8 ram chips related to waveform display.

Hope someone would like to offer some hint on where to investigate.

Many thanks in advance to all of you.

Enrico

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