DEC AXV11-C analog board

[Douglas Taylor]

Update on this:  I did put together a battery and voltage divider to 
test the AXV11.  The label on the A/D module says it brings the output 
from the multiplexer to one of the external pins.  I was able to verify 
that the voltage applied to a couple of the A/D inputs makes it through 
the multiplexer when selected using the CSR.  The next output available 
is from the Sample and Hold, and this is always pegged at +12v.  Am I 
wrong to assume that the sample and hold will 'freeze' its output when 
the A/D go bit is set?

At least the D/A's work on the AXV11 I have!  Glass half full.

Next tried the Data Translation DT2762 with the voltage divider source 
and this board appears to work correctly.  What I was able to observe 
was by applying different voltages to the input I see different binary 
values in the DBR.

The manual from bitsavers for this board lists a complete Macro 
diagnostic program in an appendix. Does anyone have an electronic copy 
of this Macro code?  Or the compiled utility?

Doug

On 2/6/2022 1:55 PM, Jerry Weiss via cctalk wrote:
> These A/D systems use methods to isolate the sensitive analog signals 
> from the electrical noise and ground plane of the computer.  Typically 
> a differential input is standard, so you will probably need wire up 
> two inputs.
>
> If this is your first time with A/D, suggest you toggle in some code 
> to trigger and report the A/D conversion repeatedly and use a small 
> voltage battery with a potentiometer divider to drive the inputs.      
> Most of the analog inputs should be high impedance and while not 
> impervious, can take +- 30v w/o damage.
>
>  Jerry
>
>
>
>
> On 2/6/22 11:43 AM, Douglas Taylor via cctalk wrote:
>> Yes, I am putting 1 into the CSR to start the conversion and I do get 
>> a 200(8) indicating that the conversion is complete.  I wonder if 
>> this means the A/D chip is OK but something else, like the 
>> multiplexer chip or gain amp is fried.
>>
>> On 2/6/2022 12:33 PM, Jerry Weiss via cctalk wrote:
>>> Are you triggering an A/D conversion via the CSR or external 
>>> signal?  Then check the A/D done bit.
>>>
>>> See  EK-AXV11-UG-02 Chapter 4.
>>>
>>>    Jerry
>>>
>>> On 2/6/22 11:20 AM, Douglas Taylor via cctalk wrote:
>>>> I have one of these and would like to use it, however it appears to 
>>>> only partially work.  Here is what I have found that works and what 
>>>> doesn't:
>>>>
>>>> 1. CSR and DBR are present and operational.
>>>>
>>>> 2. Jumpers set to 'factory'.
>>>>
>>>> 3. D/A portion works, can deposit codes in ODT and see voltages out 
>>>> on DAC pins that change depending on the octal value deposited in 
>>>> CSR+4 or +6.
>>>>
>>>> 4. A/D portion returns full scale code, either 3777 (2's 
>>>> compliment) or 7777 (offset binary) whether in the input is open or 
>>>> shorted to gnd.
>>>>
>>>> I think the problem is that the A/D inputs are not exactly 
>>>> protected and damage has occurred to this portion in the past.
>>>>
>>>> Does anyone have any info on the A/D module?  Who made it? Can you 
>>>> open it up?  Does XXDP have a test for this?
>>>>
>>>> Doug
>>>>
>>