tolcty Posted August 18, 2011 Report Posted August 18, 2011 Hi guys. I have a few questions. Can I use 2n3055 instead tip3055? And how do I connect two such devices to receive power supply positive and negative voltage? If you can please give a picture. Quote
audioguru Posted August 18, 2011 Report Posted August 18, 2011 Hi guys. I have a few questions. Can I use 2n3055 instead tip3055? And how do I connect two such devices to receive power supply positive and negative voltage? If you can please give a picture.The latest parts list for the improved circuit shows real 2N3055 transistors in a metal case, not little TIP3055 transistors that might melt.The transistors have only a positive supply, no negative supply. Opamp U3 has a negative supply.Maybe you are looking at the original project that is full of overloaded parts and does not produce 30V at 3A.Maybe you want to make a 0V to 30V positive supply and a 0V to 30V negative supply? Quote
tolcty Posted August 18, 2011 Report Posted August 18, 2011 Maybe you want to make a 0V to 30V positive supply and a 0V to 30V negative supply?Yes. I want to make a power supply for both positive and negative voltage. To be able to connect the amplifier circuits for testing and tuning. This scheme I liked it because it has a current limit that is very important. But unfortunately it is only a positive voltage.The latest parts list for the improved circuit shows real 2N3055 transistors in a metal case, not little TIP3055 transistors that might melt. Sorry, have not looked at the parts list. now look :-[ Quote
audioguru Posted August 18, 2011 Report Posted August 18, 2011 You can easily make a negative supply from a second circuit that is completely separate from the first positive circuit (also a separate transformer winding) if you use its positive output as the 0V and use its 0V as the negative output voltage. Quote
audioguru Posted August 19, 2011 Report Posted August 19, 2011 And so you can connect?No.The positive input (ground) to the negative regulator is shorted to its positive output (ground).The negative regulator needs a transformer winding, bridge rectifier and filter capacitor that are completely separate from the circuit of the positive regulator. Quote
tolcty Posted August 19, 2011 Report Posted August 19, 2011 And so right? I am a beginner in electronics so I do not understand some things. And my bad English ... Quote
audioguru Posted August 19, 2011 Report Posted August 19, 2011 And so right?Yes. Your new circuit is correct. Quote
tolcty Posted August 20, 2011 Report Posted August 20, 2011 This is great. Now I can make a new power supply. Thank you for the scheme. I hope that no more questions. No problems there. What is TB4? What is a shunt resistor should I put it? Quote
audioguru Posted August 20, 2011 Report Posted August 20, 2011 What is TB4? What is a shunt resistor should I put it?"TB4" is not on my parts list and not on my schematic. Where did you see it?A shunt resistor is used in a current-meter. Quote
tolcty Posted August 20, 2011 Report Posted August 20, 2011 Where did you see it?Reply # 1602 I downloaded the file. There is a scheme and PCB. Now I realize that TB4 is output for current-meter. Quote
audioguru Posted August 20, 2011 Report Posted August 20, 2011 In reply #1602 you are looking at PicMaster's schematic and pcb. His "shunt resistor" is R7 on all the other schematics and senses the output current. It is 0.47 ohms for 3A max and is 0.27 ohms for 5A max. It can also be used as the shunt resistor in a current meter. Quote
tolcty Posted August 21, 2011 Report Posted August 21, 2011 Thank you! No more questions. I will start the construction. Quote
fikic Posted September 12, 2011 Report Posted September 12, 2011 Hy guys. I've made a little mistake, when I connected a diode bridge. I accidentally swapped - and AC connector. I then saw some smoke and litle bang. On the output of psu, I now only get constant 33V and I can't regulate it. I thought, that opamps may be the reason and I replaced them, but this is not the case. So, what should I check next. What could happen in that case, when you swap - and AC of rectifier.PS.: PSU worked perfect before that. Quote
audioguru Posted September 12, 2011 Report Posted September 12, 2011 Hy guys. I've made a little mistake, when I connected a diode bridge. I accidentally swapped - and AC connector. I then saw some smoke and litle bang. On the output of psu, I now only get constant 33V and I can't regulate it. I thought, that opamps may be the reason and I replaced them, but this is not the case. So, what should I check next. What could happen in that case, when you swap - and AC of rectifier.PS.: PSU worked perfect before that.Your mistake might have damaged the BD139 driver transistor or the 2N3055 output transistors. Quote
fikic Posted September 12, 2011 Report Posted September 12, 2011 I replaced BD139 with BD135, becouse I don't have any BD139 left. Is this ok? How can I check 2N3055 transistors - I don't have transistor tester. Should one conduct between base and emmiter and between collector and emittor? If not, where it should? Quote
audioguru Posted September 12, 2011 Report Posted September 12, 2011 I replaced BD139 with BD135, becouse I don't have any BD139 left. Is this ok?The unregulated positive voltage is higher than 42V (when there is no load) which is very close to the max allowed voltage of 45V for a BD135. A BD139 is rated at 100V.How can I check 2N3055 transistors - I don't have transistor tester. Should one conduct between base and emmiter and between collector and emittor? If not, where it should?A transistor is measured like two diodes. The base-emitter is one diode and the base-collector is the other diode. When a diode is forward-biased then it should conduct. With reverse bias then a diode should not conduct. But some ohm-meters use a voltage that is too small to turn on a diode.A transistor should not conduct between collector and emitter unless it has base-emitter current to turn it on.Since your output is always 33V then the 2N3055 transistors are probably shorted from collector to emitter. Quote
fikic Posted September 12, 2011 Report Posted September 12, 2011 Ok, so Ohm-meter must show nothing between collector and emmitter of 2n3055, becouse it's infinite resistance? Mine show something between 100 and 200 kOhm (on both of them, on one even less). Quote
fikic Posted September 12, 2011 Report Posted September 12, 2011 I changed output transistors and it works. I get maximum 24V on output. Is this ok? Quote
audioguru Posted September 12, 2011 Report Posted September 12, 2011 I changed output transistors and it works. I get maximum 24V on output. Is this ok? If you use a 28VAC or 30VAC transformer at 4.2A then the max output should be higher than 30VDC at 3.5A and the calibration trimpots should reduce the max output to 30VDC at 3.0A. Quote
fikic Posted September 13, 2011 Report Posted September 13, 2011 No, I have 3A version with 24V AC toroid transformer. Quote
audioguru Posted September 13, 2011 Report Posted September 13, 2011 No, I have 3A version with 24V AC toroid transformer.Didn't you see the latest parts list?To have a 30V DC output then the transformer must be 28V AC or 30V AC.Since your transformer is only 24V AC then the max output will be only 24V DC or 25V DC.The transformer must have a currenty rating of 4.2A AC for the output of the project to be 3A DC.Since your transformer is only 3A then the max continuous output current is only 2.1A DC. Quote
fikic Posted September 13, 2011 Report Posted September 13, 2011 My transformer is 250VA, so current isn't the problem. So 24V output is just fine? Quote
audioguru Posted September 13, 2011 Report Posted September 13, 2011 My transformer is 250VA, so current isn't the problem. So 24V output is just fine?Your transformer has an output voltage too low so I don't know if the maximum output voltage from the project at a current of 3A is 24V DC or 25V DC. It might have excellent voltage regulation at 24V DC but produce a lot of hum riding on 25V DC. Quote
fikic Posted September 15, 2011 Report Posted September 15, 2011 With this hum, you mean just noise, or it has impact on quality of output? Quote
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