[0-30 Vdc Stabilized Power Supply]

yea im not sure,

im in new zealand, but even things like TL081 which i found in the end. for $1.61NZD. thats less then $1 US and the 2n3055 for $2.20NZD. maybe the OPA445 is just rare

and thx. ill try one of the 44V op amps

[0-30 Vdc Stabilized Power Supply]

Hi,

I am using HA17741 op amps which are rated at below the almost 40V supplied to them. for a 36V op amp. tho replacing them for the TL081 wouldn't really fix that would it, they are 36V also? 

Which is why they failed. or so i think they did. not sure how to test that. U1 and U3 have voltage but point 3 and 4

and U2 ther is no voltage. maybe i can trace the circut back from U3 untill i find the voltage?, donno heh

OPA445 are $34.10 each. thats around $15 - 20 USD. does anyone know of somthing rated between TL081

and OPA445. thats between 36V and 50V? I did find some US suppliers for cheaper then that but then the postage kinda makes it pointless

If not i guess its the OPA445, in the end i don't want somthing thats going to just melt.

[0-30 Vdc Stabilized Power Supply]

Hi,

I've just finished making this PSU, and even tho it seems to run ok. a bit hot atm but ill pick up some bigger heatsinks soon enough. I want to learn a bit more about how it works.

eg

How to work out how much heat things might generate and what heatsink is going to work best

D8 is a 5v6 zener but seems to have around 5.8V. will it change much if i find a way to make it the correct voltage? and why, D7 isn't quite right either.

Is ther a way to work out the efficency of a circut ?

This might be a bit off topic but if somone can point me to some info about this kind of theroy.

I have checked out the theroy article forum. well i still am :p

Thanks

[0-30 Vdc Stabilized Power Supply]

Thx for the info audioguru,

it seems the PSU works better with the correct value at R7 0.47 and not 47ohm

now that i can run it over 50mA, looks like i will have to find some better cooling for this power transistor :p 15V at 2A for a few mins and the whole heatsink is pritty hot. small heatsink tho

[0-30 Vdc Stabilized Power Supply]

Hi,

I have made the standard PSU from the projects page, and am after some help with troubleshooting.

the few changes in parts

-TL081 for HA17741, which seem similar.
-C1 is a 4700uF / 63V
-C4 i used two 53nF
-Q2 is a TIP31C, with bent legs to fit the original PCB design
-Resistors are half watt, R1 1W, R7 5W
-D7, D8 is a 5v6 zener tho im not sure the power rating, i can check if the problem seems to point to this
-transfo is 72VA, 24VAC output
-RV1 . ther is some confustion about this, 100ohm trimmer resistor, not a 100k trimpot? still not really sure what the difference is.

The problem seems to be the current regulation.

I can't seem to get more then 50mA out of the PSU.

I can run a LED at 2V draws about 40mA.

25V bulb that is spose to run at 750mA  i think, measures 33ohm, i donno if you can measure the expected current like that ? :o Draws about the same at 50mA if i set the voltage at 25V before load it goes to 8V with this bulb on it. There is a faint light.

Also a 3A load, voltage drops to 0.1V or so

Current pot at full off . volts measures -0.06 and the LED is on. if i turn (current pot) it up 10% or so the voltage goes up to 0 which is when the LED turns off. This is with no load.

volt pot at 100%
Voltage at the output is 32.00V
C1 33.8V
D8 5.7V

I have read both this thread and the 5A+ mod thread and i did find a few things around page 20 and some interesting things around page 76 but not really anything the same as the problem i have

Im just after it to actually work right before i change a few things which i do plan on.

Thankx for any help.