Leader LPS-152 power supply teardown - Page 1
Forum section: electronics / testgear

author: arantius
author_rank: Newbie
timestamp: August 01, 2015, 01:25:29 am
content: I've just acquired a Leader LPS-152 power supply, which I can't find anywhere on the forum besides one thread that recommends it. I posted a little teardown tomy blog(head there for larger images), and I'll copy it here as well:Here's the front panel. A couple minor scratches and scuffs, but quite good overall. Analog meters, but they're fine for the purpose. This is a triple output supply: it has one output that goes from 0V to 6V, and up to 5A, plus one each that goes from 0 to +/- 25V, and up to 1A. I'll rarely if ever use the negative supply rail, but it's possible to combine them to produce up to 50V safely. The first thing I did was test all three, and they work great, both to set the voltage and to limit the current.I managed to find a copy of the instruction manual online (the internet is great!), which has not only a complete set of operating instructions, but detailed testing and calibration procedures as well. Plus a full parts list, PCB layout diagram, and schematic! There's a ton of passives and discrete diodes and transistors. And only four ICs, all opamps. The design dates this item a bit. So let's open her up and take a peek inside!First we've got an overall view, from above. The front of the supply is at the left, with the giant heat sink at the rear is on the right side of the image. The giant transformer dominates the image at the top middle, with a black metal bracket bolting it to a support crossing the width of the supply. I like the attention to detail in here. Most everything is attached to the PCB that fills the background of the image. Next we see the smaller "meter board" first from the back, and then the front/outside, where several pot's knobs are accessible through a cutout in the body of the supply. This is how you perform the calibration procedure from the manual.Test points are liberally sprinkled across the board, with voltages clearly marked on the silkscreen. I'll certainly be able to repair things if that ever proves necessary. And I had to take note of the four huge transistors across the back. They're obviously doing the bulk of the regulation work. I looked into the schematics of various supplies for a bit as I was shopping around, trying to understand why they are so expensive. It didn't help; several schematics fit easily on a single page, and (at least for the basic models) are virtually all just a beefy linear regulator tied to an opamp or to to control regulation. The same goes here except that the circuit is all discrete parts. Not a linear regulator IC, but discrete components set up to do the same job.Finally let's wind down with some fun smaller points. As I said above there are only four ICs. Two of them (one smack dab in the center, one nearly hidden by shadow in the top right) show a likely date code: 24th week of 1988, which if correct means this is a twenty seven year old unit, and still working great. The capacitors are mostly very hard to see, but as best I can tell, like this one that is clearly visible, they're all Nippon Chemicon, which is a top quality brand. Probably helps explain why this thing still works great after almost three decades. Also a fun product design note: the power button is (appropriately) on the front panel, but the actual switch is all the way in the back. A metal rod carries the force all the way along the body. Look carefully and you can see a tiny set screw holding things together. Another indicator of quality design; a price-optimized unit would probably have done something cheaper like a friction fit, more likely to wear out, possibly beyond repair, over time.

author: iXod
author_rank: Frequent Contributor
timestamp: October 08, 2017, 02:19:06 am
content: I also have an LPS-152 (got it for free), but with borked output. Now that Dave has introduced us to the Chinese DPS- series of cheap PS modules I'm tempted to gut the Leader except for the transformer and source supply components (or I may get larger ones to boost the max output ) and installing 2 modules.And the mod'd firmware too!iX

author: bjcuizon
author_rank: Frequent Contributor
timestamp: October 08, 2017, 03:28:59 am
content: Nice teardown! Thanks for posting.I also loved reading your comments about it.I like how they did the cabling/wiring. It is really neat and tidy.

author: zitt
author_rank: Regular Contributor
timestamp: July 19, 2018, 03:25:30 am
content: Picked one of these off ebay which was suppose to be functional.It arrived with no voltages.The seller refunded my money and let me keep it.I tore it open thanks to this guide and found a lot of problems.First and form most; someone had taken it apart (assume for repair) and didn't put all the screws back in it... specifically the rear heatsink didn't have enough screws. This lead to one of the BJT transistors mounted to the back heatsink breaking at the leads. Likely due to the heatsink moving during shipping. I repaired it by soldering some wire to the remaining leads and then soldering it to the secondary side. Finally there was an open power rectifier in the 6V section; I replaced it with a "coil" diode I bought to replace the 1n400x series diode usually found on pinball machines. This seemed to fix the "6V / 5A supply".There were some questionable soldering jobs where a previous owner attempted to fix some burned traces. I re-did this work with some used solderwick brading and that seemed to help stablize some of the voltages.I found a shorted switching diode in the +25V supply. I repaired it with a 1n4148 I had in my repair box.Finally; I had an issue with the -25V supply which was only outputing 0.7V. This took several days to debug... I tested resistors; diodes; ect in the system. No joy. Finally; I did a closer exam of the rear heat sink mounted transistor... I noticed it had seen better days; maybe replaced once or twice. Upon review of the Base; there didn't appear to be a trace connecting to the pad. I pulled out some rework wire and wired it up. Now all the voltage work now.A lot of work; but the end result is I was able to fully calibrate the meters on the device.Today; I got myM3 screws kitfrom Amazon and was able to put it all back together and put it on my new workbench. I used M3 x6mm and x8mm to put it back together properly to protect those transistor leads.

author: JS
author_rank: Frequent Contributor
timestamp: August 31, 2018, 12:53:08 am
content: I just got myself one, will come back next week when I have it, I plan to run a few tests and see how it behaves itself. I haven't found any nice review on it so far, and there are a lot on different sellers around.Nice thing is the seller wants me to go to his place and test it before taking it, 300km but I was planning a trip in that direction for this weekend so everything fits nicely, back in my lab I should run a few test to know the thing more in deep and finally decide if I keep it, the price is very reasonable and agrees with international pricing, something that doesn't happen very often here. The pictures on the publication looks nice, I'll let you know when I get it.I guess a recapping it could be a good idea, even those nice nippon could get dry after 30 years, but I don't know when I'll be able to get such nice caps so it's worth it to do so. If I start to get my hands into it some mods could be nice, like 10 turn pots, a 3rd position on the switch to make it independent, not tracking, and some other that might come as it goes. Documentation is pretty nice, looks easy enough to fix which is nice for this devices.JS

author: JS
author_rank: Frequent Contributor
timestamp: September 06, 2018, 07:38:36 pm
content: Here is my look on it, I invite you to have a look!https://www.eevblog.com/forum/testgear/online-score-and-review-leader-lps-152-lfg-1300s-(work-in-progress)/JS