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| Data Precision 2020 Function Generator repair |
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| srb1954:
Thanks. This connector pin-out will be very helpful if I ever have to connect a logic analyzer to the system. |
| srb1954:
The attached schematic extract may help your investigation. This isn't for the Data Precision 2020 AWG but is from the Analogic/Data Precision 6000 Universal Waveform Analyzer. This is also an MC68000 based design so it is likely to share some design features with the 2020 logic. This reset circuit incorporates both a supply voltage detector and a watchdog time-out, both of which override the reset circuit and force the CPU into reset. Helpfully, there is a jumper link which can be used to disable both the voltage detector and watchdog and allow the reset circuit to only function as a normal power-on reset. If you can identify a similar link in the 2020 reset circuit it should greatly facilitate debugging the circuit if you can disable the watchdog and voltage detector circuitry. Note the reset voltage detector is likely to be completely separate from any power fail signal from the PSU; the PSU power fail signal will provide an early warning of impending power failure and allow the CPU to save critical data before the power fails totally. The reset voltage detector will force an immediate reset on the CPU and unsaved data will be lost. Sorry about the poor quality of the scan but the original itself is barely readable. |
| srb1954:
--- Quote from: ioprev on April 12, 2020, 02:37:53 pm ---Started debugging the main logic board today, however it's a bit difficult to take measurements on the board while it is inside the board drawer. Then noticed that there is a 64-pin header on the back side of the main logic board so I decided to follow the traces from this pins; most of them are directly connected to the 68000 processor socket. For anyone that may visit this in the future, here is the pinout of this debug header (Attachment Link) Now I quickly noticed that on mine the clock is running but ~RESET and ~HALT lines are kept at zero volt. Will not continue searching on the reset circuit. Here is the clock signal: (Attachment Link) --- End quote --- Did you ever get your 2020 going? I managed to get mine going after repairing the PSU and another fault in the reset circuit. It is a really interesting piece of test gear to play with but you need to spend a lot of time reading the manual to figure out how to best use it. |
| ioprev:
Coming back to this thread as I got another scrapped 2020 unit. Fortunately the logic board was good on this one so just swapped it to the old one that has been 4 years in storage… And it finally booted! Now, out of curiosity, started swapping the PALs between the logic boards and the one named CZ5 seems to have done the thing. I suppose the old one was gone. I think I already know the answer, but is there any way to backup the config of these PALs? Tried hooking on up in TL866 and all I got is a bunch of 0xFF. That should mean that they are protected, right? Also found a user manual here: http://manuals.repeater-builder.com/te-files/MISCELLANEOUS/ANALOGIC%202000,%202020%20User.pdf |
| ioprev:
Another question (maybe a noob’s one): My other unit has the MAX354-9920 PSU installed in it. In terms of voltage, current and ripple measurements it works fine though every time it is turned off I can hear a clicking noise for like 20 secs from it; it kind of reminds me the noise old CRTs were making. Any idea what could be the source or the noise? Is yours making the same noise when power is cut? |
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