Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I would like a schematic for a bench power supply with +/- output. I have a couple of ct transformers in the 35 to 40v secondary outputs. Any available here? Thanks, IA
There are very easy ways to do it if your input voltage is below about 30 volts and your output currents below say 1 amp. Above those it gets more complicated. So make sure of what you really need before we start,
Okay Ron, I will tell you what I have done, remember I am new at this. I found a schematic for a ps that used a 25-25v sec. trans. I built it on a board from radio shack. It worked but was kind of sloppy so I ordered a pcb and made it again. I have not found the problem but for some reason I cannot get over 10v. It starts out at 2v as it should and go smoothly to 10v at the end of pot travel. So, I happened to have a real nice trans, that puts out 33 acv on both sec legs so I thought why not go for a higher output as long as I am doing this. I have no particular reason to have it, just something to do in my retirement and stay out of certain peoples way. I don't know yet what each thing does exactly and probably will never know but I sure have fun soldering stuff together. (no fires yet). Anyhow that is what I am trying to do. I will put sch. and pcb here to show you what I have done so far. Thanks for the interest. IA
I agree. But having said that it should still work. Measure the voltage at Vin on the 317. You can futher isolate it by removing the pot. The voltage should jump to maximum.
Q1 and Q2 are mounted directly on the 20K pots. If those were removed along with pots you wouldn't have variable supply v which would defeat the purpose. I was told by seller that c9 and c10 could be removed which I did with no results. This board was originaly designed for a pre amp and was modified for variable power supply. The resistors are all as called for. The pots were to be 2K ohm ganged but are difficult to find so was changed to 20K ganged but I used seperate pots first and then tried ganged and made no difference. Do you think r3 and r5 could be the problem?
PS I also tried several different trans., even the one with 33v and got 10v output. Of coarse 317 and 337 started to get warm with the high v but made no difference on output.
Update. I removed transistors Q1 Q2 and get almost 18v. On the pcb above you will see there are R4A-R6A,R4B-R6B in parallel. I have used the B's for the two 2K2 resistors. Instructions say to use one hole each of 6A-4A to run wires to pins 3 and 6 on pot. Grd on 1 and 4 on pot. With transistors removed the pot does not regulate. Taking wires off 3 and 6 on pot make no difference, still 18v. The parallel resistors can be seen on pcb above. This is with a new 25.2 trans. As I said I built this on a bread board I guess you c
all them and it worked. Maybe have to go back to that. Any Ide
PS Please disregard this post, I have figured it out. Thanks for the help.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
