Author Topic: Knick J152 (Current), S252 (Voltage) DC calibrator  (Read 227 times)

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Offline little.teslaTopic starter

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Knick J152 (Current), S252 (Voltage) DC calibrator
« on: May 29, 2024, 08:07:59 pm »
I've just repaired two power supplies of a J152 and S252 calibrator with a lot of issues and I want to share my experience with you. The PSU has a marking 3010 from which I assume they use the same PCB for the 3010 calibrator.
On both power supplies I had to replace all of the carbon resistors, since many were open circuit, apart from the ones which were blown. Furthermore, transistors blown, Z-Diode not working, TEA1039 blown and Optocouplers were not ok

The first replacement part I've got did not work from a seller from France. The second "batch" from the USA contained genuine parts and they did work.
For a check, supply the TEA1039 with 14V from a lab power supply (in circuit) and one should see the saw-tooth waveform on the frequency setting capacitor and a square wave on the output of the IC. If this is missing the TEA1039 does not work.

BUX87    450V, 0.5A
BUX85G    450V, 2A
FJPF5021    500V, 5A <-- used as replacement

TCET1200 <-- used as replacement

On the primary side there is a regulator with a transistor and a Z-diode which provides the supply for the TEA1039 until it starts up. After that it gets its power from an dedicated winding of the transformator. This regulator has to deliver 14V to the TEA1039 else the PSU will not start. On one PSU the z-diode was bad and the voltage increased to ~20V after some time where the TEA1039 went into a overvoltage mode and did not work properly.
The feedback can be tested by supplying the 5.2V PSU output with 5.2V and as well supplying the TEA1039 with 14V. As a basic test when varying the voltage on the 5.2V the output of the optocoupler should follow the input of the optocoupler.

All capacitors (except ceramics and foil) were replaced with new ones. Tantalum replaced with Al-electrolytic

Measured output voltages:
« Last Edit: May 30, 2024, 07:45:43 am by little.tesla »

Offline little.teslaTopic starter

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  • Country: ch
Re: Knick J152 (Current), S252 (Voltage) DC calibrator
« Reply #1 on: May 29, 2024, 08:10:08 pm »
For performing adjustment of the instrument one does need a so called "Passzahl" (unlock code). Does anybody know this unlock code?

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