BK 1743 power supply coarse V pot

[ledtester]

Hi all,

I picked up a BK 1743 power supply for $5. It's missing the coarse voltage control pot (VR1).

Does anyone have a schematic or an idea of what it should be? All of the other front pots are B25K, so I guess it stands to reason that it should also be that value 

[coromonadalix]

I would try it with the same value B25k  ......  do a listing of the ic's in it, try to find the main regulator ic if there is,  it maybe build around op amps too

An user manual,   no schematics
https://cdn.testequity.com/documents/pdf/bk/1743B_manual.pdf

[ledtester]

While I wait for a B25K pot I hooked up a 15K resistor and a 10K pot. Was able to adjust the output voltage from 0 to about 12.7V so I think 25K R is the right value.

The only ICs on the board are a CA324E and a CA723CE - so basically an LM324 op-amp and the classic 723 voltage regulator.

[Ordinaryman1971]

Just to confirm, it is 25k pot. I’ve just opened mine up.

[mawyatt]

Just to confirm, it is 25k pot. I’ve just opened mine up.

If the pot is used as a proper pot (3 effective wire) rather than a variable resistor (2 effective wire) a simple solution to get you back up and running until the proper 25K pot arrives is get whatever pot you have on-hand that is higher in resistance (say 50K or 100K) and place a parallel fixed resistor (50K or 33K) so paralleled result is 25K. This usually works well when used as a voltage divider (proper pot use), but also when the pot is used as a variable resistor (the knob position relative to output is non-linear tho).

Best,

Mike