spectrum analyzer tektronix 2710
Hello,
the failure mode "analog only" seems to have a different cause. However, the cause might reside within the same PLD (U352, PLS173).
Attached is a draft address-map of the display-storage board. Although I believe that the information is correct, there may be mistakes. (If you find one, please write a short note for correction -- thanks)
If the analyzer can still be controlled by the front-panel keys, you may try the following tests -- even if you can't see the menus on the CRT:
DISPL_MENU > 6
Switches the readout on and off. Performs a write to the register inside U260 via LAT2. Register contents cannot be probed directly, but you should see a short write pulse on LAT2 as well as EW-.
DISPL_MENU > 4
This toggles between MINMAX and PEAK acquisition. Signal PEAKDIS should change high or low, respectively. A test for writes to latch U460.
DISPL_MENU > 3
This should toggle HLF/FLL-. Another test for writes to U460.
In both cases, you should see a write pulse at U460's CLK Pin 11.
UTIL_MENU > 5 > 2 > 2
This writes checkerboard-like patterns to the four digital storages and shows them (only waveforms, no text).
After presssing any key, shows the character set all over the screen (only text, no waveforms).
Again pressing any key, shows both checkerboard and character set (text and waveform displays on).
Press UTIL_MENU again to leave.
In your case, you will probably see nothing, but you might be able to see the write pulses at the RAM U436 Pin 27 (WE-) when the CPU writes text/waveform data to it.
To detect the sparse write pulses, you will need a (digital) storage scope or a logic analyzer.
UTIL_MENU > 5 > 1 > 1
This is the "DISPLAY STORAGE DATA ACCUM" test. Data is continuously read from the ADC by the CPU via the REDAT- line, and is written to the display RAM. So you should note pulses on U438 Pins 1 (ER-) and 7 (REDAT-), and on U436 Pin 27 (WE-), probably also on U352 pin 27 (UPMEM-).
NOTE: This test is not run if waveform A contains saved data, indicated by the green LED besides the "A" key. Press SAVE > A to clear this.
Regards,
Andreas.