[SOLVED]Tek TDS744A slow refresh or recovery

[Daxxin]

applyng signal or changing channel very very slow to refresh even with the input disconnected remai sine trace on the screen to refresh need to
change trigger channel or rotare h or v , look like something wrong with video ram, sometime slow but recover sometime not like ch3 in the video.-
never own scope like this before but i guess its not regular.
look at the video.

https://youtu.be/QaDCtnPcZgU
 

[Jwalling]

I suspect it's because you are using ET sampling *and* averaging. Save the setup and post it here and I'll try it on a TDS784A.

[Daxxin]

I suspect it's because you are using ET sampling *and* averaging. Save the setup and post it here and I'll try it on a TDS784A.

Hi Jwalling , here the setup i will try to different set  , here setup attached

[Jwalling]

The only difference I noted is that when I inputted the signal to CH3, then set the trigger to CH3 (From CH1) the signal resolved quickly, where yours seems to sort of fade in but never looks very good. Have you run the full self test from the utility menu as well as SPC?

[Daxxin]

Your right i get processor error with the test with following gpib log

ERROR: diagnostic test failure, dsp68kD1MemTest, ** addr = 0x720a680  exp data = 0x5555  actual = 0xff55, ** addr = 0x720a682  exp data = 0x5555  actual = 0xff55, ** addr = 0x720a684  exp data = 0x5555  actual = 0xff55, ** addr = 0x720a686  exp data = 0x5555  actual = 0xfd55, ** addr = 0x720a688  exp data = 0x5555  actual = 0xff55, ** addr = 0x720a68a  exp data = 0x5555  actual = 0xff55, ** addr = 0x720a68c  exp data = 0x5555  actual = 0xfd55, ** addr = 0x720a68e  exp data = 0x5555  actual = 0xfd55"

[Jwalling]

I have a few failures in my logs that may be of some use. These were pulled from the console port.

U1009-17 shorted to VCC:
dsp68kMemTest .................. ***FAIL***
..error details:
ERRORID: 153 diagnostic test failure dsp68kD1MemTest
** addr = 0x7200000  exp data = 0xf7ff  actual = 0xffff

and

U1009-17 SRAM open etch:
dsp68kMemTest .................. ***FAIL***
..error details:
ERRORID: 153 diagnostic test failure dsp68kD1MemTest
** addr = 0x7200000  exp data = 0xf7ff  actual = 0xffff

So maybe that memory chip or associated circuitry. U1008 may also be suspect.

[Daxxin]

thanks for sharing the info , its ok to replace with AS6C1008-55SIN?
i seen have 2 additional not populated sram expansion U2008 and U2009 , theres benefits to install also them?

[Jwalling]

thanks for sharing the info , its ok to replace with AS6C1008-55SIN?
i seen have 2 additional not populated sram expansion U2008 and U2009 , theres benefits to install also them?

That seems like a suitable replacement, but I'm not saying that one of the chips is defective. It could be some other device that's associated with the circuit.

I would not install memory where none ever existed in the first place.

[andy2000]

Start by checking for broken solder connections.  I had a 744A that developed some bad connections around the large memory controllers which caused memory errors.

[Daxxin]

  i'm too late reading yours replies..  i have 2 M5M51008 but 100ns instead 70ns replaced alredy , well before the test very short (run 30 seconds without any graphical shapes tests) then i was getting
processor fail , now seems the test is running very long then at the end i'm getting the banner instead the result and the scope freeze stucking on the banner , do you think slower sram can cause this?
by the way ordered alredy the correct sram.

[Jwalling]

i'm too late reading yours replies..  i have 2 M5M51008 but 100ns instead 70ns replaced alredy , well before the test very short (run 30 seconds without any graphical shapes tests) then i was getting
processor fail , now seems the test is running very long then at the end i'm getting the banner instead the result and the scope freeze stucking on the banner , do you think slower sram can cause this?
by the way ordered alredy the correct sram.

Is switch 3 on the dip switch set on or off?

[Daxxin]

i'm too late reading yours replies..  i have 2 M5M51008 but 100ns instead 70ns replaced alredy , well before the test very short (run 30 seconds without any graphical shapes tests) then i was getting
processor fail , now seems the test is running very long then at the end i'm getting the banner instead the result and the scope freeze stucking on the banner , do you think slower sram can cause this?
by the way ordered alredy the correct sram.

Is switch 3 on the dip switch set on or off?

this the actual dip switch positions

[Jwalling]

Then it sounds like something happened when you replaced the chips. Could be that the access time is too slow, or a damaged trace from the removal process.

[Daxxin]

Replaced with 2 new 55ns M5M51008 everything fine thanks Jwalling for the inputs was a big big help , i will post video soon  , very fast now changing settings from front panel.

[Jwalling]

You're welcome!