Jump to content
Electronics-Lab.com Community


  • Posts

  • Joined

  • Last visited


Divljo's Achievements


Newbie (1/14)



  1. well, I've got some bad news :) I left supply 15mins with 15V and 2.85A and measured voltage drops for op amps and some components... pin 4 of U3 gets -0.02V :) R7 1.1V D6 2.4V D7 -1.1V and then something happened; Q2 started to smoke and I quickly turned off supply...it seems it is ok; checked E and C voltages; i turned on supply and with load nothing happens (maybe it needs time to screw up?) Q2 is cold as ice all the time but when he started to smoke he was very hot :) Also, R2 and R3 are hot! Both they need to be minimally 1W but I'll buy 2W C2 is getting only warm, but is there any way to cool him down completly? Higher voltage? And now the list of non-working components :) C3 has 215Ohm resistance; -dead D7 isn't anymore diode; it lets current flow through both ways -dead And now something weird...D11 is dead! Maybe it happened when Q2 started to smoke ;D Rest seems to be OK But, I'm going day after tommorrow to buy again all diodes, op amps and some resistors and some other things..and I'm gonna make new PCB, hope it is the last pcb for this project :)
  2. I replaced D7 and there is same thing! Nothing happened! I changed positions of U2 and U3 to see if one of them is burned but everything stayed the same! I checked voltages at U3 and they are all 0V except pin 6 (35V) and pin 7 (35.6V) What is the next element that I should look? Later I will put back Q1 but I don't think circuit will work then... And I removed R23&24 and regs from PCB...I'll put them on other trafo
  3. well, you are wrong - LED is still working even without reg circutry And current pot isn't working! Is it possible that U3 is damaged? Neverthless, I ordered from TI free 5 samples of OPA445 :) I haven't tried putting Q1 back but i think it wont work because in the first place, reg circutry wasn't connected when Q1 was in his place and circuit didn't work... I must say that drop on D7 is 0.1V..that should be 5.6V, right? And other Zener, D8 has drop of 5.1V...even that is confusing (at least to me ;D )
  4. I forgot to tell you that you were right for R23 resistor! He is so damn hot!
  5. Well yeah, it works at last ;D But current pot isn't doing nothing! No matter where I turn him, current stays the same! Voltage and current is cotrolled through voltage pot! And yes, they are properly connected, there is no problem with that... And what with Q1? Why isn't circuit working with it? And I connected VoltMeter and it showed -000 and I connected out of the power supply and from then VM shows 000 and on last segment b,c and g segments are flashing! And display is half seconds brighter and then some time is normaly lighted and again brighter and so on... I think I burned 7107 ;D
  6. I disconnected Q1 and it works! With Voltage pot I can change from 32 to 2.4V but there is more turning space and when I turn, voltage rises instantly to 35V! LED is always on, no matter where I turn Current pot I connected 50W 5Ohm resistor and then voltage drops to 22.9V max and minimum is 2.5V, and once again, at same end of pot, voltage rises to 22.9V Current is controlled from 4.47A at max to 0.47A. And here I get again 4.47A at same end of pot! I just figured out that I cannot control current output! If it stands at lowest value (0.46A) Voltage pot must be also at lowest value (2.5V) When I increase voltage, current also goes up...wtf? ??? I just burned my finger on 2N3055 where I connected collector wire! Other one that is connected through heatsink is only warm! Is that normal? This is at minimal current and voltage...
  7. My mistake for Q1! It has 0.6 drop at base, not at collector! So, U2 is dead now? I don't see any shorting and I checked it with multimeter buzzer! Will new one TL081 work? And my R14 is 1.5K; do I need to lower to 1.2 due to my trafo is only 24V? I've disconnected voltage regulators and R23&24 because I thought they are causing problems but everything stayed the same...and yes, that is pseudo 0V but why I get on negative side only -0.7V drop? Thomas: Wher do you see that pin 2 is connected to the input of 79xx? pin2 of both regs are connected to gnd! btw audioguru, are all other voltages except U2 proper? And is there any other op amps possible to put except 445 and two others which name i don't recall now ;D ?
  8. Oh, I forgot to put links to PCB...here it goes...
  9. Hi everyone! I've built this power supply but it doesn't work...at output it gives 0.2V all the time! Strange thing is when I disconnect power, voltage rises to 2.9V and then lowers to 0V! And U2 is SO DAMN HOT just after few seconds after powering up! I've been using some modified components from the list and also I modified PCB to nicely put TIP31 tranzistors; and I putted 7805 and 7905 voltage regulators to make +-5V for 7 seg LED voltmeter project also from this site... I use 10 000uF cap, 25V 100VA trafo, 2 2N3055, and I hadn't found even opa445 or other two suggesteg OP AMPs in store so I left TL081.. Well, in theory, I think I didn't made any mistake in circuit projecting, but I get these errors: 7905 on out gives 0.7V drop, not -5 7805 works great LED indicator is up all time, no matter how I turn pot.. Output voltage is all time 0.2V And this are values that I measured in circuit: U1 PIN 6 10.3V PIN 7 35.4V U2 (very HOT!) PIN 1 0 PIN 2 0.2 PIN 3 10.2 PIN 4 0 PIN 5 0 PIN 6 0 PIN 7 35.7 PIN 8 0.3 U3 PIN 6 35 PIN 7 35.6 Q1 E 0 B 0 C 0.6 Q2 E 0.2 C 35.5 B 0 Q3 C 24.9 B 35.1 E 35.8 Q4 C 35.5 B 0.2 E 0.2 Current pot: 13 - 1.6V 6 - 1.6V 11 - 0V Voltage pot: 5 - 10.3V 12 - 10.3V 10 - 0V R1 35.7 R2 4.7 R7 0V (?) D5 3.7V D7 0V D8 5.1V D9 25.6V D10 0.1V D11 0.2V C1 34.8V C2 3.1V C4 9.5V C5 35.6V C7 0V Well, that's what I've measured...hope it helps because I need soon to finish this project ;D
  • Create New...