Fixing a LQ-521 power supply. The output was stuck at 40V and there was nothing on the display. Teardown pictures can be found here: www.kerrywong.com/2016/05/07/l...
Glad it was an easy fix Kerry. Two things, first although we all love our better halves I'd take off the wedding ring when poking around a circuit that can deliver high voltage/current and second for the long term health of that supply I'd change out the resistor that "smoked" since it probably was severely heat stressed. Now that the nit-picking is over, good job, always enjoy following along with your adventures! ;-)
+Dino Papas Thanks for the suggestions! I will keep that in mind. Regarding the burnt resistor, I will definitely replace it once I have a suitable one. It's a 182 Ohm 1% film resistor. I didn't have one on hand.
+Kerry Wong Having been on the wrong side of a 600VDC supply in a ham radio transmitter I was building in high school (back in the dark ages!) I'm a firm believer in the no jewelry and one hand in the back pocket rules! Keep the videos coming!
Good video Kerry! I was a technician for 20 years and used to keep a log of any tough problems I found. You'd think once you go through fixing a tough dog, you would not forget the solution. So wrong! Just subscribed to your channel. BTW it seems like a great supply. I'm searching for a small linear supply that will output 0-20 volts at 450 ma. It has to be quiet a possible to be used for RF. Cheers, John
I have a pair of LP-532 FM's. So far one checks out. I will have to take a look at the other. These have analog meters, and 60v. The wiring may be messy, but this one lasted quite a long time. I may recap mine. I likely will shoot a video of it.
Cool. Congrats. I picked one up not working also. Luckily mine was an easy fix. The display was dead on mine also. Turned out the power supply driving the display had bad filter caps. You might want to change out some of those silver caps with the red tips on them on yours. A couple looked like they were bulging.
Hey man, I have one of these that is like new in the garage, have no idee what it was, googling it to find out what it was and found ur video... gosh what u didn't mention was how damn heavy they are!!!!!!!!!!!!!!!!!!!!!!!! Mine is a LQ-532... if you or anyone is interested in it I can toss it on my ebay sales account just let me know!
Nice video. Glad it was an easy fix. I am a big fan of Lambda products. I have a few of their older supplies, and some new switch mode (non-lab) supplies. All are rock solid. Keep an eye on those old capacitors on the control board. I have had to replace them in my supplies. They go high ESR and the units cannot put out their rated current. Does yours have a nasty overshoot, or is it a meter issue when the display jumps up to over 60V when you first switch it on late in the video (a meter with min/max or a scope will tell you of course). Thanks again.
+PelDaddy I think it's a meter issue. I did a single shot with my scope during turning on and the curve is pretty smooth, without any overshot. Those caps are fine for now, but I probably should change them down the road as these old caps could fail at any time.
Dang, take the ring off your finger when working on stuff like this, if not for the safety practice but to ensure you never risk making a very short someplace that damages more parts and makes for more work .... (speaking from personal experience).... :-)
Does it affect the operation of the power supply? If the power supply works normally and the transformer does not overheat, this would suggest that the core is simply loose, you can either live with it or reapply some epoxy glue. There is a possibility that there could be a short somewhere in the transformer but you would find that out pretty easily (just let it sit idle for a while and check if there's any unusual heating from the transformer).
Kerry Wong Thank you. It works perfectly well. I just use it for an audio application (to power a field coil speaker driver), so the buzzing sound is not a good thing. I guess I will open it and apply some epoxy. Thanks again.
Hi. One of my Lambda's works decent, but could use some new capacitors. The other one is in pretty rough shape. I may not repair it...yet. czcams.com/video/EbHv09j7gXc/video.html
Leaving that cable diagram saved you a headache Kerry, good fix, thanks!
Glad it was an easy fix Kerry. Two things, first although we all love our better halves I'd take off the wedding ring when poking around a circuit that can deliver high voltage/current and second for the long term health of that supply I'd change out the resistor that "smoked" since it probably was severely heat stressed. Now that the nit-picking is over, good job, always enjoy following along with your adventures! ;-)
+Dino Papas Thanks for the suggestions! I will keep that in mind. Regarding the burnt resistor, I will definitely replace it once I have a suitable one. It's a 182 Ohm 1% film resistor. I didn't have one on hand.
+Kerry Wong Having been on the wrong side of a 600VDC supply in a ham radio transmitter I was building in high school (back in the dark ages!) I'm a firm believer in the no jewelry and one hand in the back pocket rules! Keep the videos coming!
Nice repair and now you have a high quality power suppy, please clean up the front and make it look nice again....
Nice repair and now you have good power supply with current limitation.
Good video Kerry! I was a technician for 20 years and used to keep a log of any tough problems I found. You'd think once you go through fixing a tough dog, you would not forget the solution. So wrong! Just subscribed to your channel. BTW it seems like a great supply. I'm searching for a
small linear supply that will output 0-20 volts at 450 ma. It has to be quiet a possible to be used for RF. Cheers, John
Nice repair video, another piece of kit saved from going to the dumpster.
+VoltLog Thanks!
I have a pair of LP-532 FM's. So far one checks out. I will have to take a look at the other. These have analog meters, and 60v. The wiring may be messy, but this one lasted quite a long time. I may recap mine. I likely will shoot a video of it.
Cool. Congrats. I picked one up not working also. Luckily mine was an easy fix. The display was dead on mine also. Turned out the power supply driving the display had bad filter caps. You might want to change out some of those silver caps with the red tips on them on yours. A couple looked like they were bulging.
Great! Thanks!
Just snagged a 531 with the same condition on the output.. peaked inside, oh dang... banks of transistors. Looks like I'm gonna have fun!
It's a pretty decent power supply, I am sure you'll enjoy it.
Hey man, I have one of these that is like new in the garage, have no idee what it was, googling it to find out what it was and found ur video... gosh what u didn't mention was how damn heavy they are!!!!!!!!!!!!!!!!!!!!!!!! Mine is a LQ-532... if you or anyone is interested in it I can toss it on my ebay sales account just let me know!
Nice video. Glad it was an easy fix. I am a big fan of Lambda products. I have a few of their older supplies, and some new switch mode (non-lab) supplies. All are rock solid. Keep an eye on those old capacitors on the control board. I have had to replace them in my supplies. They go high ESR and the units cannot put out their rated current.
Does yours have a nasty overshoot, or is it a meter issue when the display jumps up to over 60V when you first switch it on late in the video (a meter with min/max or a scope will tell you of course). Thanks again.
+PelDaddy I think it's a meter issue. I did a single shot with my scope during turning on and the curve is pretty smooth, without any overshot. Those caps are fine for now, but I probably should change them down the road as these old caps could fail at any time.
Good afternoon, master
Please see the schematic diagram of this power supply!
Thank you, sir !!!
Wow , those to 3 packs , I thought they only came only as 317regs or transistors
Dang, take the ring off your finger when working on stuff like this, if not for the safety practice but to ensure you never risk making a very short someplace that damages more parts and makes for more work .... (speaking from personal experience).... :-)
I have the similar 531 which is in like new condition, except the transformer buzzes -- can anyone help me fix it? Thanks
Does it affect the operation of the power supply? If the power supply works normally and the transformer does not overheat, this would suggest that the core is simply loose, you can either live with it or reapply some epoxy glue. There is a possibility that there could be a short somewhere in the transformer but you would find that out pretty easily (just let it sit idle for a while and check if there's any unusual heating from the transformer).
Kerry Wong Thank you. It works perfectly well. I just use it for an audio application (to power a field coil speaker driver), so the buzzing sound is not a good thing. I guess I will open it and apply some epoxy. Thanks again.
I have a lambda lt-802 and the screen just flashes. I can't adjust voltage or current. Any ideas ?
Do you have any output from the PS? If it's stuck at maximum then it's most likely one of the bypass transistors is shorted.
Please !!!
how much did you pay?
Don't remember for sure but I think I paid around $30 for it.
Hi. One of my Lambda's works decent, but could use some new capacitors. The other one is in pretty rough shape. I may not repair it...yet.
czcams.com/video/EbHv09j7gXc/video.html