Datron 1061 refurbish AC board miss information about SU2656M JFET

[xantia_99]

Hi,

i change this from the repair part of this community, I hope You do not mind ...


i have refurbish my old Datron 1061, Analog board, Digital board, power supply. Together with resistance and current board it work excellent . Put in a MAT12 and AD711 after that it worked very good. Problem with change a lot of chip, passive components sockets, drivers, optical ..
Now it works and very stable.

Today or shall i say the last year refurbish the AC-board. instability and not possible to make a zero calibration. To much noise
Lost hfe in 2N3905, 2N214C and so on. Many measurement traditionally  with diode tester  ok , but no gain with curve tracer. Found 6 transistor without/low gain until now from input to TL7. The differential Q21 and Q22 did not match. Now its possible to calibrate but it's not stable

Now my problem:
I miss information about  Teledyne double jfet SU2656M  to make it possible  to measure with a curve tracer to see if I have to exchange them
I am on the right way.  I have spend to may hours but I have retired so ..

I am a bit tired of all this but want to finish with AC-board at the same level as new or better. If I will get everything to work very good I will change the display. But it cost i know that I have asked.

Best Regards
S