[0-30V Stabilized Power Supply]

i see.... right now the LED is light up after i change the capacitor but without U2 and U1 in place,  still looking in local store here.

[0-30V Stabilized Power Supply]

after browsing old posting. i found that picmaster pcb drawing has a fault on C10 or C3 if using audioguru schematic it is + and - of the capacitor is backward in the pcb. and i found mine was backward and it is now shorted maybe this is the cause of the U1 and u2 blew?

[0-30V Stabilized Power Supply]

ok... i have to wait the new op-amp from digikey. will inform you later.

btw can i use opa445? i have few in the drawer.

thanks

[0-30V Stabilized Power Supply]

what should i do? when P2 set to 3.8V the ZD 10V and op-amp is impossible to touch i think it will blow too if i set to long.

[0-30V Stabilized Power Supply]

hi all specially Audioguru,

i build with mc34071, 24VAC transformer and picmaster PCB layout... yesterday i blew two op-amp U1 and U2. i trace from u3 when i turn P2 until 3.4-4.0V on R18 u3 and ZD 10V become very hot. and i think when those op amp blew i set the P2 more than 3.4V.... what's wrong?


regards,
ali

[0-30V Stabilized Power Supply]

You have a serious problem with your -5.6V supply. Replace R2 and C2.

just replace R2 with higher watt, 5W and C2 with branded one still -2.1V with full load. output still stuck at 28.5V.
R7 because i have difficulties to find one so i use 4 1Ω parallel is it problem?

thanks

[0-30V Stabilized Power Supply]

Q1, R13, R14 remove now and the output at emitter Q4 +29.8V collector +31.5V

without load (remove all ICs) it is -5.6V. with load (all component) except Q1, R13, R14 is -2.1V

thanks

[0-30V Stabilized Power Supply]

Q1 is used when the U2 opamp is a TL081. Q1 is not needed when the U2 is almost any other opamp.
I think your Q1 is turned on all the time because something is wrong with your negative -5.6V supply.

so i just remove the Q1, R13, R14, R15, D10 correct?

I think something is wrong with your negative -5.6V supply. Measure it.

is it in D7 i have to measure the -5.6V?

thank's

[0-30V Stabilized Power Supply]

U2 pin 3 0V to +11.2V checked, U1 pin 6 +11.27V, but when i put the Q1 U2 become Hot so right now i disconnect Q1. i have  swap the BCE of Q1 but the U2 still hot.



i can not measure output voltage because i disconnect Q1 and Q2. but at collector Q4 is 30.5V



i use the part list for the OPA445 as you post at the beginning of this thread. R2 82Ω 3W and R3 220Ω 1/2W


thanks

[0-30V Stabilized Power Supply]

Hi audioguru,

just finished soldering all the component using old schematic + old pcb layout with OPA445 and 25Vac 6.25A toroid. but there is a problem the output can not be adjust? and the U1 is slightly hotter than the others. do you have test point what the voltage should be at that point so i can check it.

and R2 and R3 is really hot around 40-60 celsius is this normal?

thanks

[0-30V Stabilized Power Supply]

ok

Thanks audioguru.

[0-30V Stabilized Power Supply]

hi audioguru,

i have opa445 on hand right now, so which schematic should i use?

thanks,

[0-30V Stabilized Power Supply]

They use extremely low power which shows because they are much too slow. Their output drops above only 800Hz. They are also very noisy.

Thanks audioguru for the answer

[0-30V Stabilized Power Supply]

hi all,

is it possible to use LT1491 for the op-amp? coz i have few on my drawer

thanks,