UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Mini-drill; Speed Controller Problem

orbanp1 · 28th Nov 2017, 4:04 pm

Hi Bazz,

If you do not want to wait for the LM358 IC to arrive, just give an additional -5V supply to the negative Vee pin-4 of the IC (instead of tying it to the ground), then it should work.

When the regulator chip works correctly, then there is 1.25V difference between the Output pin of the IC and the Adjust pin. Check it with a DMM.
You need load on the output for this to work correctly, because of the high R5 resistor (1 kOhm versus the suggested 200 Ohm - 240 Ohm).

Simulation shows that with the LED diode in the circuit the output voltage does not increase with load, if you short it out (no LED) then the output voltage increases with load.

And yes, the LM358 and LM1458 are pin-compatible.

Good idea to check out that diode across the regulator chip!

Regards, Peter

28th Nov 2017, 4:04 pm	#10
orbanp1 Heptode Join Date: Nov 2009 Location: London, Ontario, Canada Posts: 675	Re: Mini-drill; Speed Controller Problem Hi Bazz, If you do not want to wait for the LM358 IC to arrive, just give an additional -5V supply to the negative Vee pin-4 of the IC (instead of tying it to the ground), then it should work. When the regulator chip works correctly, then there is 1.25V difference between the Output pin of the IC and the Adjust pin. Check it with a DMM. You need load on the output for this to work correctly, because of the high R5 resistor (1 kOhm versus the suggested 200 Ohm - 240 Ohm). Simulation shows that with the LED diode in the circuit the output voltage does not increase with load, if you short it out (no LED) then the output voltage increases with load. And yes, the LM358 and LM1458 are pin-compatible. Good idea to check out that diode across the regulator chip! Regards, Peter