Help! Knick JS 3010 DC- Calibrator Problems!

[karlseN]

 
I bought a Knick JS 3010 Calibrator on eBay! It looks in good condition and works pretty well so far. All ranges i checked were pretty much bang on!

However: It won’t let me go over 27V on the output. I can enter higher values but it won’t output them. I checked inside the unit and found several hints! It has many replaced caps and pieces of sticky tape when they were replaced! The PSU in the back seems to be self made though! It looks really good but i cant imagine knick used prototype board in those instruments 

There seems to be a +/- 300V Rail that is missing! I suspect the instrument uses that rail to derive the higher output voltages?

The cable to the board is missing. But i cant see where it should be connected to!

So Here is my question: Does anybody have a knick JS 3010 and would kindly supply some pictures from the inside?

Also if anyone has a Service manual or schematics for the unit, it would be such a big help!! There are no service manuals or anything available! Only the operators manual.

I will post some pics of my JS 3010 in the morning. I have to work night shift! Thats why i couldn’t take proper pics yet

Thank you all. I really hope someone has one on their bench

[coromonadalix]

some docs  no schematics, cant open them   because  this address is blocked by our fortinet 

https://docs.ampnuts.ru/eevblog.docs/Knick/Knick%20JS3010%20DC%20calibrator%20manual.pdf

https://docs.ampnuts.ru/eevblog.docs/Knick/         

[karlseN]

Thanks for the docs coromonadalix! I also found the Operators manual but its pretty much useless… Although i am suprised that it even exists. Finding any proper documentation of Knick equipment is basically impossible. I already looked in the Xdevs archives but no dice!

I also shot an Email to Knick in hopes of them having those service infos in their archives somewhere. Somehow i am doubtful   

[kilobyte]

I took some pictures of my JS3010 when I received it in 2017 before some cleanup of the housing and calibration. Interestingly the PCBs itself were mostly clean but there was a lot of flux residue on the top side.

[zepto]

Thanks for the pictures. I love through-hole designs.

A while back I bought an Adret 103A on ebay. The output was limited to ~27V despite being 100V capable. I thought maybe the limiter was stuck on 25V, so I opened up the case to look at the limiter. Next to the limiter buttons were the banana jacks, and there were diodes soldered across the output jacks!! I clipped them off and proper output was achieved. I guess someone really wanted to protect the device they were powering.

[karlseN]

Thanks for the replies! I have attached two pictures from the power supply inside the unit. It seems to me that the previous owner replaced the whole power supply section with something selfmade. It looks like he did not bother with the 300V node to supply the HV output section…

Actually when I received it, It had two Zener diodes in series screwed into the output terminals. Removing those did not change anything! Sadly….

Now It seems like i have to design a new power supply for the calibrator. Its nothing hard or complicated except for the Suspected +/- 300V rail… I gotta figure out how to achieve that!

[karlseN]

Heya! I wanted to check back in… I got an reply from Knick! Sadly though, as i suspected, they weren’t able to help me whatsoever. They couldn’t give me the calibration commands (Or numbers to select the desired range that is to be calibrated), nor could they hook me up with a service manual or schematics… They just sent me the operators manual   

I have been looking around for some way to get the missing voltage rail. I am not even sure that it is +-300V as the previous owner had marked inside the unit! The caps on the PCB that recieve the suspected 300V split supply are rated at 350V. Thats too close to a 300V supply for my taste at least… Also +-300V dont really make sense in my books. The unit can only output +-140V max.

I have attached a picture of the connetors on the PCB. For my german fellows: The piece of sticky tape on the Aluminum shield says something about a 300V supply being removed…

If anyone wants to throw in some ideas for the +-300V supply design, feel free to throw them in here! I would gladly take some pointers

Have a great evening!