Data Proof 320A

[doktor pyta]

some photos taken during cleaning

[bck]

Data Proof 160B/320B ?

[TiN]

These ones we do have.. 

[doktor pyta]

bck was very close: it is DP 320A

Unit arrived in very good condition but was not responsive to front panel operation.
During troubleshooting I pressed internal A (or B) 'protect defeat' button. It is not easy beacause it requires having 3rd hand.
After doing this the scanner responded to front panel buttons.
So the diagnosis was: dirty relays' contacts.
I used Techspray Eline  contact cleaner.
It took 4h to clean 64 relays...

Some photos below

[doktor pyta]

By the way: does anyone know the price of these relays when ordering directly at Data Proof?
It would be nice to have few pieces just in case.

[ManateeMafia]

Back in 2014, I was told the refurbished relays cost $55. This was the price quoted from Data Proof.

I also bought a newer GPIB board that is advertised on their website to overcome some incompatibility issues. The only problem I have had is with the NI GPIB-USB-B adapter.
My adapter would select the A side and then the B side. But while the B side was being selected, the A side would be deselected. I only have one of those adapters but confirmed it on two different scanners.

Several of my relays needed manual actuating and some fingers needed to be adjusted. No lubricant was used to clean them.

[doktor pyta]

After cleaning I checked how stable contacts' resistance is.
It may indicate the condition of the relays and/or reveal surface oxidation problem which may degrade low EMF performance.
A piece of code for controlling DP320A and Datron 1271 was written by Zbigniew169 (thank You!).
The approach is to connect in series all 4 contacts related to certain channel (figure below) and measure its resistance during 100 mechanical cycles.
Ohms current is set to 1mA.
For sake of simplicity this method does not resolve which section A or B have problem. This can be easily determined 'by hand'.

Each point on the chart consist of 100 data points.
The diferences in the resistance value is mainly due to diffrent lengths of internal wiring (these wires are very thin).
Keep in mind the resistance value is for 4 contacts in series+ resistance of internal wiring.

[TiN]

Interesting test. Perhaps if one use DP scanner for resistance, modification to make equal wiring resistance would be useful? 

[doktor pyta]

Just played a little with different chart types and found 'stock' type which presents these data more clearly (see below). I think I have problem with channels A17 and A18.
I will simply not use these channels until I get new relays (spare relay box inside is empty).

@ TiN: rather makes no sense. If someone will measure 2W ohms using this scanner he will probably connect resistors > 1Meg to keep small influence of leads resistance.

[ManateeMafia]

I believe the wiper contacts are supposed to be self-cleaning. If so, then exercising the questionable channels should show an improvement in resistance and lowered noise.

Never tested mine that way but I added an exercise routine to my scanner software. I guess it would be helpful to check it.

[doktor pyta]

I forgot to mention that I 'exercised' relays for 5 hours before these resistance measuremets.

[branadic]

Simply a beautiful construction, love to see that relays on their golden tracks. Congrats to your device. 

-branadic-

[ManateeMafia]

I came across a note somewhere about bending the contacts on the armature. It may have been in the user manual. I had some success doing this but this was mostly to cure issues with contacts not reading as closed.

I don't have any data to compare to yours but it would be a matter of modifying some python code to make measurements.