DEC AXV11-C analog board

[Chris Zach]

This is a really interesting thread, I have this darn AF01 A/D converter 
for a negative bus pdp8 and your issues and methods with testing would 
work well for testing this thing. Bonus it does appear to have a 16 or 
64 channel mux capability.

Question: Is it possible to change the driver boards for ones that do 
positive bus logic or is it simpler to build a DW08 converter clone to 
hook it up to my pdp8/L for testing?

C


On 2/13/2022 12:04 PM, Douglas Taylor via cctalk wrote:
> On 2/8/2022 7:36 PM, Jon Elson via cctalk wrote:
>> On 2/8/22 16:35, Douglas Taylor via cctalk wrote:
>>> On 2/8/2022 5:22 PM, Jon Elson via cctalk wrote:
>>>> On 2/8/22 13:34, Douglas Taylor via cctalk wrote:
>>>>> 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?
>>>>
>>>> Well, it will probably only hold the approximate voltage for a few 
>>>> seconds, but should be long enough to see on a voltmeter.
>>>>
>>>> Jon
>>>>
>>> I was only using a voltmeter to look at it.
>>>
>>> I'm going to try 2 different measurements; (1) use a scope to look at 
>>> the S&H signal on the AXV11 and see what it does over time, (2) look 
>>> at the same S&H signal on the Data Translation board which seems to 
>>> be working.
>>>
>> The S&H will likely have a FET as the switch element, and those might 
>> be fairly easily damaged by external pulses.  I opened up some 
>> comparable Xincom modules and made minor repairs.
>>
>> Jon
>>
> Stopped fooling with the AXV11 for now.  Applied various voltages to the 
> Data Translation input and recorded the A/D octal values to get an idea 
> of what the calibration of the board is.  It looks very linear, +/-10v 
> range.
> 
> Using a single battery and voltage divider I was able to generate 
> voltages on the input of the DT2762 board, however, I had to swap wires 
> to get negative voltages.  Is it possible to construct a battery driven 
> circuit that will present both positive and negative voltages at the 
> input?  A bridge of some sort?
> 
> Doug
>