HQ Power PS3010 blew up after charging a lead acid battery - Page 1
Forum section: electronics / repair

author: lxd
author_rank: Newbie
timestamp: July 10, 2025, 10:48:35 pm
content: Hi everyone,I've been jail rotting projects for way too long, decided to do something about the situation recently and sadly my lab PSU blew up which really doesn't help.It's a PS3010 badged HQ Power, 30v 10A, multiple tapped transformer with relay switching design. very cheap but does the trick for my needs.The symptoms are, transformer thumps loudly when turned on, PSU stays at 48/49 volts, no response to controls, R16 is heating up on the main PCB. If i'm correct i also remember RP2 being hot to the touchI've found the schematic inside of a Velleman PDF, model name + picture matches, some parts of the schematics dont match (no V16, no V31, no v32 neither iirc, and V17/V18 aren't populated on my pcb if i remember). Seems like my PSU predates the schematic because otherwise everything is correct (later rev on which this doesnt happen ?)I will highlight every component I tested tomorrow (and take a look at which components are there or not) but this repair makes me doubt my abilities i think it's time to fresh start, here's a small list of things i tested out of the board/swapped : 7812 was swapped but is fine, both LM741s were swapped but no change, V5 looks fine, all 2N3055 looks like transistors, relays diodes V22/V23/V24 are fine, relay transistors V25/26/27 look like transistors too, iirc i tested V28 tooHere's the schematic, sorry there's no OCR, it's a picture in the original PDF too :I'll continue my investigations, but if this rings bells, please let me know !I'm not the first one to have this issue so i'm curious at this point :https://www.eevblog.com/forum/repair/skytronic-650-682-0-30v-0-10a-psu-repair/Thanks in advanceCheers

author: indeterminate
author_rank: Regular Contributor
timestamp: July 11, 2025, 05:38:23 am
content: chk the zeners is V11 correct

author: coppercone2
author_rank: Super Contributor
timestamp: July 11, 2025, 06:31:37 am
content: two things like to kill lab supplies IMO,high test batteriessolenoidsthey would not sell battery analyzer products if it was foolproof and easy

author: BradC
author_rank: Super Contributor
timestamp: July 11, 2025, 08:35:50 am
content: Mine went pop under the same circumstances and boiled the battery. In my case it was one of the BUX48A pass transistors (probably fake) that shorted but I see you've already tested those. It cooked the 50 milliOhm current sense shunt also.12V SLA's don't like 50V @ plenty of amps for hours. Come to think of it, the transformer was pretty warm too.I replaced all the output transistors with later model MJ15003's and the .05 Ohm shunt with a low tolerance 0.047 Ohm ceramic and put a decent fan in. Probably over-capitalised but it's still working. Having said that, I tend to use an MCH-K3010D switcher now for battery charging.

author: mikerj
author_rank: Super Contributor
timestamp: July 11, 2025, 08:54:40 am
content: If the output transistors are good then I would look at the driver transistors V13 & V14. With the supply operating, what voltage do you see on the junction where the anodes of V11,V12 & V15 are connected? Note that all the control circuit supply rails are referenced to the +ve output of the supply, so put the negative of your volt meter on the +ve output.

author: lxd
author_rank: Newbie
timestamp: July 11, 2025, 08:26:34 pm
content: So, measurement took at the anode of V11/V12, i got 7,03v, V14 was a bit warm, shut it down, meaured again, 5,17vif i fiddle the knobs and let it current limit (meters are indicating 0,30A draw), now i get between -3,9 and -2,8v. Oh also the CC/CV leds are working now, they weren't before. V14 is also coldIt seems i desoldered V11, i have a component tracer on my scope and i think if i resoldered it, its that it was ok. Measured -3,8 anode, -1,8 cathode with voltmeter (currently the scope is in exploded view mode, it will request another thread... thats for another day. tracing pcbs for now lol). On diode mode it shows 1,89 gnd on cathode, 0,72 reversedV12 cathode on voltmeter i get -0,4vjust burnt the tip of my finger checking if R16 was hot... i need an el cheapo thermal camSmells like a failed junction somewhere? Doubting V13/V14. same, my solder flux is there, i know i desoldered them and tested them outside of the circuit, maybe tested them with a peak trans tester, but for sure nothing is shorted in circuit looking with a DVM, fine in diode mode too, if they were missing a junction i think i would've catched that but i will desolder if neededIt seems there is no footprint for V15, V16 isnt populated. V31 is present and looks fine, not sure where V32 is, i think there is a diode right behind the banana connectors, i remember checking it also, nothing looks shorted putting the DVM on the outputs of the PSU and looking in diode mode both ways, i get 0,0v when reversing and slowly ramping up when putting leads in the correct way.Time to check values for all the resistors? Widlarize?edit : no v18 neither. v17 is populatedreedit : it seems i desoldered relays too, i think i tested them outside circuit with a 12v psu to see if coils weren't soldered together, they have their number from 1 to 3 with permanent marker, pretty sure i remember i did this test

author: lxd
author_rank: Newbie
timestamp: July 19, 2025, 02:35:35 pm
content: small up, does anyone have any idea? I'll continue troubleshooting but i am really interested in your advice for troubleshooting this unit. thanks !