Any Datron 4705/4708 gurus here?

[Oldtestgear]

I have a working Datron 4705 and a very sick, AC only, 4708. I know that all the boards are interchangeable except for the digital control board but does anyone know the exact differences between models?
The 4708 uses the venerable LTZ1000 & should make a significant improvement if fitted to the 4705 but what about the other boards? It seems like a sound idea to me to upgrade the 4705 rather than try to fix the 4708. After all the 4708 firmware is limited for AC operation only. Have I missed anything? Opinions & hard data would be really appreciated before I start actually testing the various options.

Thanks in advance.

Phil

[ManateeMafia]

I was thinking about doing the same thing to my 4700 by updating the onboard reference.

The LTZ1000 reference is mounted on a daughterboard. I believe the connectors are the same on both boards and it would be quick to see if that's the only difference between the two boards. I don't think there are any other precision parts on the main board that are different.
Looking at a picture of the 4808 reference assembly there are two connectors that should make it easy to measure voltages.

The digital assembly has dip switches that enable features. I dropped in a resistance/current board in my 4700 and flipped the correct switches. The board was recognized. I could use the current function but the resistance section was unpopulated so I couldn't test it.

[quarks]

I do not have a 470x but 4808 and afaik, they are very similar.

So my guess is, you should be able to use your 4705 function boards in your 4708 and "activate" the  new functions via the dip-switch.
At least I would try this first, before I would desolder/transplant the reference.

good luck

[Oldtestgear]

Thanks for your inputs. Must admit that I didn't appreciate that options can be added using the DIP switches. From other things I have read, the motherboard is shared between the 4705 & 4708 as are all (?) the power supplies and 400V modules mounted immediately behind the fan. As the 4708 has multiple faults in the 400V modules, a broken mains input connector plus a few other small problems (broken display amongst others......) perhaps swapping the 4708 components into the 4705 is a sensible move.
 
Assuming that the transplant works - I can't see a reason why not  - then I have a great AC calibrator & can then either add DCV & Resistance boards from the 4705 OR dig out the Datron 4000A sitting on the floor & use this for DCV & resistance.   I will report back.


Thanks.

[chinapp]

the 4708 use more high-end part than the 4700 and 4705,some vishay resistor is better

[Oldtestgear]

Thanks for the replies & information. I have transplanted the 4708 cards into the 4705 chassis along with the 4705 cards needed for DC & resistance. It is working but readings are 2.3% high due to the different reference. I am sure this can be adjusted out when I calibrate it. All I need now is to get a DMM calibrated as a reference & this project will be finished.

I plan to get my recently acquired 3458A calibrated by Keysight in the next couple of weeks & will use that. The 3458A is another project instrument that I will write up once I know whether Keysight will give it a certificate.

Thanks again.

Phil