EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: reddish75 on December 05, 2016, 07:00:18 pm
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Hi, I'm trying to restore two BlackStar Jupiter function generators, the first of which worked of a fashion but after a recap and a clean up it seemed to work ok, however.....
when trying to follow the calibration in the service manual (see attached with thanks to Tristan at TTI) I'm either not following it properly of theres something else wrong in there.
Firstly the voltage check at Tp 7/8 are correct at -15.17v and 15.21v but then it starts to go wrong, whichever position VR4 is in VR1 just wont adjust the voltage at TP5 below 120mv >:(
So any pointers on where to look/measure/scope any help would be appreciated.
https://1drv.ms/b/s!AhyV-hIo37nZpmpKgUIKInekTCFl
Thanks
Chris
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The top side of VR4 is grounded (TP1), so when VR4 and VR1 are both set at the top (as seen in the diagram) TP5 should be zero volts.
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So VR4 should be set at the TP1 side? for the start of calibration?
Just a thought, the frequency pot VR1 where does this have to be set before calibration or does not not matter? Same with the Duty control (VR6) as well?
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Reading the calibration instructions:
2.
a) Set VR4 fully anti-clockwise. (I assume this is the TP1 side)
b) Adjust VR1 (the frequency control) to get -10mV at TP5.
So, before calibration VR1 doesn't matter, it is set during one of the first calibration steps.
I didn't see VR6 mentioned in the cal procedure at all (just quickly scanned it), but the general rule heer is don't touch it until it is mentioned.
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Thanks for posting the service manual. I just acquired one of these. Though, is there a user manual for it online too somewhere? My google-fu didn't bring anything up.