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Electronics => Repair => Topic started by: Bargainhunter on February 06, 2017, 04:49:25 pm

Title: BK Precision 1745A Now working BUT......
Post by: Bargainhunter on February 06, 2017, 04:49:25 pm

Many thanks for your help.  I now have my BK 1745 DC Power supply nearly working.  My problem now is that when I try to adjust the voltage below 5 volts the voltage gradually drops to zero unless I add a load across the output posts.  It seems like a capacitor is holding a charge.  Is this normal?  I have attached a schematic for a 1746 which is almost the same (only schematic I could find).

Any input would be greatly appreciated.

Thank you in advance,
Chuck

Title: Re: BK Precision 1745A Now working BUT......
Post by: Kleinstein on February 06, 2017, 05:59:43 pm

In the shown schematics there are 4.7 K resistors as a minimum load. So the voltage will not go down instantly, but also not that slow. I don't see a reason it should be significant slower below 5 V - just the normal exponential  decay.  Of cause the 1745 might be different (e.g. different resistor values for R1 and R3) at this detail.

Title: Re: BK Precision 1745A Now working BUT......
Post by: james_s on February 06, 2017, 06:37:28 pm

Could it have a dead spot in the adjustment pot?