audioguru2
- Apr 6, 2004
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Hi Marek,
Welcome to our forum.
Let us fix your jumpy power supply project.
First, some questions:
1) What are the output voltage and current or VA ratings of your transformer?
2) Did you build it like the original plans, or did you make any modifications that we discussed here?
3) Did you substitute any parts?
4) When the output voltage jumped when adjusted, did you have an output load?
5) When the output voltage jumped when adjusted, did the current regulating LED light?
6) Does the voltage at the slider of the voltage adjust pot adjust smoothly from 0V to 11.2V?
7) Does the voltage at the output of U2 (pin 6) adjust smoothly from about 1.3V to 27 or 28V?
8) Without a load, does anything get hot when you adjust the voltage?
Welcome to our forum.
Let us fix your jumpy power supply project.
First, some questions:
1) What are the output voltage and current or VA ratings of your transformer?
2) Did you build it like the original plans, or did you make any modifications that we discussed here?
3) Did you substitute any parts?
4) When the output voltage jumped when adjusted, did you have an output load?
5) When the output voltage jumped when adjusted, did the current regulating LED light?
6) Does the voltage at the slider of the voltage adjust pot adjust smoothly from 0V to 11.2V?
7) Does the voltage at the output of U2 (pin 6) adjust smoothly from about 1.3V to 27 or 28V?
8) Without a load, does anything get hot when you adjust the voltage?
HI
1) 22 V AC (28 DC on capacitor C1) about 5A
2) I build standard project 0-30V 0-3A
3 )Yes i substitute Q3 with BC556,Q2 with BD243C and r15 with 100 ohm. I nowhere can find 2n2219 or Tip29, Tip31.
4) I didn't load output
5) No , LED is not light
6) voltage at the slider of the voltage adjust pot adjust from 0V to 11.2 without U2.(At 6 pin is the same voltage at pin3 on board without U2). If i insert U2 the voltage is about 25V at pot.
U2) is getting hot. If i solder off pin6 U2 the temperature is normal, but is all time 27V.
Regards and Thanks for interest.
1) 22 V AC (28 DC on capacitor C1) about 5A
2) I build standard project 0-30V 0-3A
3 )Yes i substitute Q3 with BC556,Q2 with BD243C and r15 with 100 ohm. I nowhere can find 2n2219 or Tip29, Tip31.
4) I didn't load output
5) No , LED is not light
6) voltage at the slider of the voltage adjust pot adjust from 0V to 11.2 without U2.(At 6 pin is the same voltage at pin3 on board without U2). If i insert U2 the voltage is about 25V at pot.
U2) is getting hot. If i solder off pin6 U2 the temperature is normal, but is all time 27V.
Regards and Thanks for interest.
audioguru2
- Apr 6, 2004
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Hi Marek,
You made good transistor substitutions.
Your U2 is defective, replace it. It is feeding voltage to its input.
Wait a minute, it could be that you have U2's pin 3 (input) and pin 6 (output) reversed! The top of the IC looks like this:
1* 8
2 7
3 6
4 5
Wait a minute again. Without U2, its pin 6 follows its input? Then your circuit board is shorted from pin 3 to pin 6. ;D
Your transformer voltage is kinda low, so your project's maximum output voltage will also be low. If you use 10,000uF or more for C1, and a 10A or more bridge rectifier module then you will get a couple of volts more output at full load.
You made good transistor substitutions.
Your U2 is defective, replace it. It is feeding voltage to its input.
Wait a minute, it could be that you have U2's pin 3 (input) and pin 6 (output) reversed! The top of the IC looks like this:
1* 8
2 7
3 6
4 5
Wait a minute again. Without U2, its pin 6 follows its input? Then your circuit board is shorted from pin 3 to pin 6. ;D
Your transformer voltage is kinda low, so your project's maximum output voltage will also be low. If you use 10,000uF or more for C1, and a 10A or more bridge rectifier module then you will get a couple of volts more output at full load.
audioguru2
- Apr 6, 2004
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Hey, is Smartkit sending all their customers who have problems over to here??? ;D ;D ;D
Last edited by a moderator:
Hi again.
I know that U2 is placed correctly. I changed U1,U2,U3
I use 22kOhm pot.
Maybe some measure points will help me?
On board beetwen 6 and 3 pin U2 i have 28 Kohm on multimeter, beetwen pin 2 and collector Q4 is 25Kohm.
Something is wrong, and I don't know what
Regards
Marek
I know that U2 is placed correctly. I changed U1,U2,U3
I use 22kOhm pot.
Maybe some measure points will help me?
On board beetwen 6 and 3 pin U2 i have 28 Kohm on multimeter, beetwen pin 2 and collector Q4 is 25Kohm.
Something is wrong, and I don't know what
Regards
Marek
audioguru2
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Hi Marek,
Did you say that without U2, the voltage at its pin 6 is the same as its pin 3, that both pins adjust from 0V to 11.2V?
Pin 6 shouldn't do that without U2.
With U2 connected, it must be passing some of its output voltage of 27V to the pot to make it 25V instead of 0V to 11.2V.
Your resistance measurement of 28K between pins 3 and 6 of U2 depends on the output voltage of your ohm-meter. If its voltage is only about 0.3V or less, then it should measure more than 1M.
All of these observations point to leakage between pins 3 and 6 of U2. Try lifting D9 and R9 from pin 3 to see if you still have leakage from pin 3 to pin 6, or leakage from D9 or R9 to pin 6.
Hi
Yes, I said without U2 the voltage at pin 6 is the same at is pin 3.
I agree from this that pin6 shouldn't do that.
I lifted D9 and r9, at pin 3 is 0V -good. Adjust at pin 6 is still from 0 to 11 V- and this is bad.
And i found solution. I had micro short-circuit at r8 and r15.
Thank You very much Audioguru for your time and help. Such trifle, and it be able to lead out with aim man. ;D
One more time Thank You.
Regards Marek.
Yes, I said without U2 the voltage at pin 6 is the same at is pin 3.
I agree from this that pin6 shouldn't do that.
I lifted D9 and r9, at pin 3 is 0V -good. Adjust at pin 6 is still from 0 to 11 V- and this is bad.
And i found solution. I had micro short-circuit at r8 and r15.
Thank You very much Audioguru for your time and help. Such trifle, and it be able to lead out with aim man. ;D
One more time Thank You.
Regards Marek.
audioguru2
- Apr 6, 2004
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Hurray Marek,
You fixed it! I am glad to have helped. ;D
Please let us know its performance.
You fixed it! I am glad to have helped. ;D
Please let us know its performance.
audioguru2
- Apr 6, 2004
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Hi Zwieke,
I couldn't find a datasheet for a 2N6578, but got conflicking reports about its power dissipation ability, either 87.5W or 120W on an infinite size heatsink at 25 degrees C. So it might burn.
It's a darlington transistor so has an extra B-E voltage drop, which will reduce your project's maximum output voltage.
I wouldn't use it, 2N3055 transistors are very common and inexpensive.
I couldn't find a datasheet for a 2N6578, but got conflicking reports about its power dissipation ability, either 87.5W or 120W on an infinite size heatsink at 25 degrees C. So it might burn.
It's a darlington transistor so has an extra B-E voltage drop, which will reduce your project's maximum output voltage.
I wouldn't use it, 2N3055 transistors are very common and inexpensive.
Hi all 1st post here
And to start quickly here are some questions...
1) On post #93 someone asked about higher Voltage rating Caps can be used (change a 50V to a 250V) but he went to sleep
So is it possible ? The voltage rating of caps refers to how quickly does the Cap releases its energy ?
2) IS there an updated PCB image yet ?
3) In a previous post you audioguru say
"Our project doesn't specify a part number for D6"
But i see on the project page that says D6=1N4148
In the end shall we use the BZY79C5V6 you suggest ?
Or you did a typo, and you meant changing D7 and D8 ??
And to start quickly here are some questions...
1) On post #93 someone asked about higher Voltage rating Caps can be used (change a 50V to a 250V) but he went to sleep
So is it possible ? The voltage rating of caps refers to how quickly does the Cap releases its energy ?
2) IS there an updated PCB image yet ?
3) In a previous post you audioguru say
"Our project doesn't specify a part number for D6"
But i see on the project page that says D6=1N4148
In the end shall we use the BZY79C5V6 you suggest ?
Or you did a typo, and you meant changing D7 and D8 ??
Last edited by a moderator:
audioguru2
- Apr 6, 2004
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Hi Ngt,
Welcome to our forum.
1) The guy with the 250V caps did go to sleep when he realised that they were actually 450V ones and said, "forget it".
The voltage rating of a cap has nothing to do with the way it operates. Just how much voltage it can withstand without breakdown.
2) A few guys talked about making an updated PCB but nobody posted one.
3) OOOps, I did make a typo. Sorry!
D8 is this project's main voltage reference and should be a BZY79C5V6, and also D7 which is the voltage regulator for the negative supply. D6 is just a low current rectifier.
Also, R4 should be changed to 1K for 5.6mA throgh D8.
I have corrected my posts.
Welcome to our forum.
1) The guy with the 250V caps did go to sleep when he realised that they were actually 450V ones and said, "forget it".
The voltage rating of a cap has nothing to do with the way it operates. Just how much voltage it can withstand without breakdown.
2) A few guys talked about making an updated PCB but nobody posted one.
3) OOOps, I did make a typo. Sorry!
D8 is this project's main voltage reference and should be a BZY79C5V6, and also D7 which is the voltage regulator for the negative supply. D6 is just a low current rectifier.
Also, R4 should be changed to 1K for 5.6mA throgh D8.
I have corrected my posts.
Hey Audioguru i made in 3 days time the original circuit in Express PCB.
Anyone has got the skills to make it match with the modified parts ??
PSU_0-30V_0-3A.zip
Anyone has got the skills to make it match with the modified parts ??
PSU_0-30V_0-3A.zip
Last edited by a moderator:
audioguru2
- Apr 6, 2004
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Hi Ngt,
Thanks, that's a nice PCB, especially in vivid red.
Who is going to construct and report the performance of the first one?
Thanks, that's a nice PCB, especially in vivid red.
Who is going to construct and report the performance of the first one?
teixeiramg
- Nov 5, 2004
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Hello!
Does this project use a trimmer of 100k or a trimpot of 100k?
Thanks,
Marcelo
Does this project use a trimmer of 100k or a trimpot of 100k?
Thanks,
Marcelo
audioguru2
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Hi Marcelo,
Welcome to our forum.
RV1 is a 100K trimmer resistor that is set only one time, to adjust the offset voltage so that the project's output voltage is exactly zero volts when its voltage adjust pot is turned down.
Select a trimmer resistor that fits your PCB.
Note that this forum discusses changes that we made to the original project to make it work better.
Welcome to our forum.
RV1 is a 100K trimmer resistor that is set only one time, to adjust the offset voltage so that the project's output voltage is exactly zero volts when its voltage adjust pot is turned down.
Select a trimmer resistor that fits your PCB.
Note that this forum discusses changes that we made to the original project to make it work better.
Hi I'm Tom from Hungary .I'v made the PSU twice.2X28V AC in,C1=4700uF/50V,rectifier is diode bridge 4A,all ICs TL080(must komp.cond.betweenpin1-8 100pF) pots are long peridot type (icould
scale them almost linear both amp. and Volt. Max.output 25V/3.2A .It works correctly 1pc 2N3055 is enough..Heat sink are rather big.I 'v designed a new PCB with Protel,if somebody interested in I'll send the work.Thank U for the projekt,and a very polite and correct ideas.
scale them almost linear both amp. and Volt. Max.output 25V/3.2A .It works correctly 1pc 2N3055 is enough..Heat sink are rather big.I 'v designed a new PCB with Protel,if somebody interested in I'll send the work.Thank U for the projekt,and a very polite and correct ideas.
