Leader Power Supply 735-10D Service Manual - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: October 25, 2022, 01:18:38 pm
content: I have a Leader Power Supply 735-10D and it has an odd problem. I found the manual (https://www.massetrecovery.com/Pictures7/leader7185d.pdf) but not any schematics, but it doesn't provide schematics.I'm assuming the schematics don't exist, so maybe someone has had experience repairing a similar issue in the same or another power supply; or has an idea where to start looking.It seems when I first turn it on, the display is about 1.5V less than the measured output (i.e. at 10V output the display will read 8.5V). Eventually the display is correct and matches the output voltage. This is either because I turn the dial and exercise the relay(s) or something heats in the display circuit. It's hard to tell because if I turn the knob, I need to measure the voltage and I'm uncertain if turning the knob caused the display to change or the display changed while I turned the knob. If I let it sit, it doesn't seem to change, but it always seems to just being working correctly at some point while I'm tinkering with wires to connect to something.This isn't a big problem as I usually always measure the output voltage regardless, but would like to fix it.Has anyone had a power supply that did this and what was the problem?Since the voltage doesn't seem to decrease by 1.5V and the display jumps to 1.5V, this tells me the problem is within the display circuit that measures the voltage. If I turn it off for some amount of time, the display returns to being low which tells me the display is the portion that is acting up. Also, I'm uncertain if the display is 1.5V less across all voltages. As I mentioned, the more I tinker with it, the quicker it seems to begin working correctly so I somewhat haven't narrowed it down to figuring out which happens first.

author: urbite
author_rank: Newbie
timestamp: August 23, 2025, 11:26:01 pm
content: Can you PM me the document that you have? I found the same link as in your post, but the link isn't working.

author: bostonman
author_rank: Super Contributor
timestamp: August 24, 2025, 02:07:59 pm
content: It's not scanned well but it's all I found online.Let us know if you find any schematics. As stated though, the problem isn't serious, so unless I find an easy fix, it's really not worth my time (at least for the moment) to tinker with it.

author: Gertjan
author_rank: Frequent Contributor
timestamp: August 24, 2025, 04:39:51 pm
content: Hi bostonman,To me the picture in the linked manual does not look like Leader at all:Leader-Power-Supply-735-10D-front-2000pix.pngTo me this looks more like a Volteq orMastech power supply.These power supplies are sold under many brand names. I think this was a rebrand that Leader sold under its own name.So I think you should search for Mastech etc. schematics, and see if one is matching with your power supply.regards, Gertjan.

author: bostonman
author_rank: Super Contributor
timestamp: August 25, 2025, 01:05:34 am
content: The manual wasn't valuable once I discovered it didn't have schematics, but good to know it was sold under different names.Mine looks like the one on the right; although I'm not looking at mine to get an exact match.

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 25, 2025, 01:22:24 am
content: it's an OEM of GW Instek GPR-3510HD. but doesn't seem to be a circuit diagram.Tektronix has a GPC based model PS280, but is that any reference?https://w140.com/tekwiki/wiki/PS280MOD:I found a partial schematic, but how useful will it be?

author: MathWizard
author_rank: Super Contributor
timestamp: August 26, 2025, 11:21:53 am
content: I just bought an older PSU with dial meters, and 1 of them didn't work because a 2-wire connector header had broken loose the solder pads.It could just be a bad solder joint around the digital meter circuit, or other part that works better after warming up.