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Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)
- Thread starter bushtech
- Start date
If R7 measures 0.002V and pin 2 of U3 connects to R7 through R21 then how can pin 2 of U3 be 0.94V? Does the output of the project measure +0.93V? Then something is shorting it to the positive voltage. R7 is 0.47 ohms. 0.94V/0.47 ohms= 2.0A which is a lot of current and where is it coming from? Maybe C8 is shorted a little and is causing the pin 2 voltage. Try replacing C8.
Another problem. P1 is supposed to feed 0V to 11.2V to pin 3 of U2 (measure it) and U2 has a voltage gain of about 2.7 times so its output should go from 0V to about +30V. But if the LED lights then the input of U2 is reduced by U3 driving D9. Then the U3 problem with its pin 2 voltage being too high is not fixed.
It is a good idea to replace all the cheap Chinese junk (Bangnogood).
The output of U2 is its pin 6 that should be 2.7V higher than its input pin 3: 0V in = 0V out. 2V in= 5.4V out. 10V in= 27V out. 11.2V in (max)= 30V out.
Pin 3 of U2 is fed through R8 and R9 from the slider of the voltage setting pot P1. It should go from 0V to 11.2V as the pot is turned but it is probably wrongly clamped through D9 by whatever is affecting U3. C4 might have the same leakage problem as C8. Disconnect D9 to see if U2 works properly without D9. If not then also disconnect C4.
Audioguru, Ok, If U2 's only job is to V from 0 to 30V when P1 is turned then U2 is working fine (acually 34.4V fine) And Pin 3 to 6 ratio is about 2.7x. This is with new U2. Don't know why it's working, as long as it's stable.
Now, as soon as I get a gap, I'm digging into the hot U3
Thanks again for all the help
Now, as soon as I get a gap, I'm digging into the hot U3
Thanks again for all the help
Audioguru, Ok, If U2 's only job is to V from 0 to 30V when P1 is turned then U2 is working fine (acually 34.4V fine) And Pin 3 to 6 ratio is about 2.7x. This is with new U2. Don't know why it's working, as long as it's stable.
Now, as soon as I get a gap, I'm digging into the hot U3
Thanks again for all the help
Now, as soon as I get a gap, I'm digging into the hot U3
Thanks again for all the help
This is where it gets a bit weird. I couldn't really understand why it suddenly started working. But then I noticed that I had lifted the one leg of D9 to check it. So I soldered the one leg of D9 back and checked it again and I'm back to about 7V max. So D9 has got something to do with the weirdness. Btw D9 checks out fine with deflection one way
The way the current regulation works is using U3 to reduce the output voltage by using D9 to reduce the input voltage of U2. Then if you set the current setting at 1A but the voltage is set to 10V and the load is 5 ohms then U3 senses way more than 1A and reduces the input voltage of U2 so that the current is 1A then output voltage of the project is 1A x 5 ohms= 5V.
Pin 2 of U3 is supposed to be almost 0V when there is no load but you measured 0.94V which is causing the output of U3 to drop from its high of about +30V and reduce the input of U2. Measure the voltage at both ends of R21 (it should be almost 0V) and measure the resistances (without power to the circuit) of R21 (10k) and R7 (O.47 ohms). The negative output of the project should be almost the same voltage as the 0V of the negative end of C1.
Pin 2 of U3 is supposed to be almost 0V when there is no load but you measured 0.94V which is causing the output of U3 to drop from its high of about +30V and reduce the input of U2. Measure the voltage at both ends of R21 (it should be almost 0V) and measure the resistances (without power to the circuit) of R21 (10k) and R7 (O.47 ohms). The negative output of the project should be almost the same voltage as the 0V of the negative end of C1.
That was needed to test U2 by itself.
First, you need to fix whatever is causing the voltage on pin 2 of U3 to be a positive voltage higher than almost 0V.
Thanks Audioguru
Working back from Pin2 of U3:
Pin 2 = 0.93V
to
R21 = 0.93/0.002V (still in situ, leg not lifted) Reads 9.95kΩ
to
Connection point R4 = 0.002V
to
CP R6 = 0.002V
to
Pin 4 of U1 = 0V
So components behind R21 all at 0.002V. I don't understand how voltage could jump from 0.002 to 0.93V going through a resistor.
Have I discovered the world's first free energy source?
Working back from Pin2 of U3:
Pin 2 = 0.93V
to
R21 = 0.93/0.002V (still in situ, leg not lifted) Reads 9.95kΩ
to
Connection point R4 = 0.002V
to
CP R6 = 0.002V
to
Pin 4 of U1 = 0V
So components behind R21 all at 0.002V. I don't understand how voltage could jump from 0.002 to 0.93V going through a resistor.
Have I discovered the world's first free energy source?
Audioguru, you are on the money! Looking in the wrong place I was.
Which brings up the question: Did I correctly turn the transistor around. Here is the link to the BD 139 I am using. As far as I can see the pins are reversed to the original 2SD9015
http://www.mantech.co.za/Datasheets/Products/BD139-STM-82U.pdf
Which brings up the question: Did I correctly turn the transistor around. Here is the link to the BD 139 I am using. As far as I can see the pins are reversed to the original 2SD9015
http://www.mantech.co.za/Datasheets/Products/BD139-STM-82U.pdf
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