Velleman LABPS3005DN power supply - Page 1
Forum section: electronics / testgear

author: blurpy
author_rank: Regular Contributor
timestamp: November 13, 2019, 12:29:25 pm
content: I have a Velleman LABPS3005DN power supply, and it has an annoying speaker that beeps whenever you do anything.It's hard to find any details about it, but Velleman rebrands some equipment, so I'm wondering if anyone recognizes this under a different brand? Maybe there is a known fix.Product details:https://www.velleman.eu/products/view/?id=439082

author: Black Phoenix
author_rank: Super Contributor
timestamp: November 14, 2019, 05:10:21 am
content: Open the PSU, desolder the buzzer, done.

author: blurpy
author_rank: Regular Contributor
timestamp: November 14, 2019, 07:46:26 am
content: Thanks for the tip. I'm a bit of a newbie on these things, so not sure I'm comfortable to start there.Is it usually safe to remove a buzzer from a circuit like that, without affecting anything else?Guess I'll have to open the case anyway. But wondering if it would work to muffle the buzzer with electrical tape or something?And any safety tips when opening and working on a PSU?

author: Tepe
author_rank: Frequent Contributor
timestamp: November 14, 2019, 07:54:51 am
content: Quote from: blurpy on November 14, 2019, 07:46:26 amUnplug it

author: Gyro
author_rank: Super Contributor
timestamp: November 14, 2019, 09:55:17 am
content: Quote from: blurpy on November 14, 2019, 07:46:26 amYes, definitely try muffling it with a piece of tape or sticky label across the hole first. Those bleepers work as a resonant enclosure, so covering the hole usually makes a big difference.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: November 14, 2019, 11:32:25 am
content: Hello!It looks like a lot to Korad and RND models. Try this.Beep On / OffPanel OperationBy default, the beep sound is enabled. To turn off he beep, press the OCP (BEEP) button for 2 seconds. A beep comes out and the beep setting will be turned off.To enable the beep, press the OCP (BEEP) button again for 2 seconds.I hope this can help!

author: blurpy
author_rank: Regular Contributor
timestamp: November 14, 2019, 12:21:41 pm
content: Thanks for the suggestions!When I get home I'll try the OCP trick first, then if that doesn't work I'll unplug it () and try to muffle the buzzer.

author: blurpy
author_rank: Regular Contributor
timestamp: December 09, 2019, 07:03:34 pm
content: OK, I've had some time to look into this again.I could not get the OCP trick to work. But I've added some tape to the buzzer. It still makes a noticeable beep, but it's not so sharp and loud anymore. So definitely an improvement

author: blurpy
author_rank: Regular Contributor
timestamp: December 10, 2019, 07:31:29 pm
content: While I was at it, I did a partial teardown, since there's not much information about this PSU anywhere. I didn't remove the circuit boards to take the pictures, as there was a lot of glue everywhere.There's 4 boards. I'm making some guesses on some of the chips.1. USB boardSilicon Labs CP2102 USB to UART BridgeIsocom IS124 AC Input NPN Phototransistor Output Optocoupler (FPT2)2. Power boardD880YW Low Frequency Power Amplifier NPN Transistor2x HF(Xiamen Hongfa Electroacoustic) JQC-3FF 12V RelésThere's 1 really big chip and 2 big ones on the pcb pushed against the heat sink. Can't see any details.Also, not sure what brand those caps are.3. Display boardTM(Shenzhen Titan Micro Elec) TM1639 LED Driver4. Main boardPIC16F887 CMOS FLASH-based 8-bit microcontrollerST 78M08 Linear Voltage RegulatorChangjiang Electronics Tech CJ78M05 Linear Voltage RegulatorLM336Z25 2.49 V, 2% Programmable Shunt RegulatorMB10S Bridge RectifierDB107S Bridge Rectifier4x NXP 74HC595D 8-bit serial-in, serial or parallel-out shift register with output latches; 3-state7x Texas Instruments OP07C Low-Offset voltage (0.25mV) single operational amplifierTerminals, with ground cable and what looks like a huge 1N540X diode.On the backside of the pcb there is a crystal of some kind, and the buzzer from the previous post.In addition, there are a whole lot of misc components everywhere.I don't know if it's possible to conclude on the quality of this power supply based on what we see here? I don't have a clue.

author: grizewald
author_rank: Frequent Contributor
timestamp: December 10, 2019, 08:32:04 pm
content: It's probably a reasonably competent design, and it's good to see that quite a lot of safety features are present, but the actual assembly is very poorly executed.In your last picture, for example, it's great to see an earth wire properly attached to the chassis with a star washer and even thread lock on the nut. However, in the same picture, I can see a blob of solder which has damaged the insulation on the earth wire, what seems to be a large solder splash on the leg of the 1N540x Schottky diode and the PCB is also covered in tiny solder balls (probably from the splash on the diode).Other pictures show a general disrespect for cleaning off flux residue properly and the picture with the PIC MCU shows poor cleaning and what seems to be some kind of corrosion in whatever the hole is down to the bottom left of the MCU.The 78M05 regulator seems to have been placed with its legs in the air and it's lucky there was enough solder paste to make a connection.Where they've soldered the low voltage outputs from the transformer to the plug on the PCB is comical! I guess the plug and matching connector couldn't handle the current?The electrolytic caps are, at least, rated to 105°C. I don't recognise the logo though.If it was mine, I'd be preparing a large batch of flux remover and stripping that PSU down to the individual boards for proper cleaning and removal of all the solder balls and splashes. Then fixing a few dodgy solder joints and finishing the job of shrinking some of the shrink wrap that they just gave a cursory swipe with the hot air (like on the transformer).

author: blurpy
author_rank: Regular Contributor
timestamp: December 11, 2019, 04:15:07 pm
content: Thanks for the analysis @grizewald!You are noticing a few more details than I did. I am a bit surprised by how dirty it was inside (and it's quite new). I'll take your suggestion on fixing it up a bit.

author: grizewald
author_rank: Frequent Contributor
timestamp: December 11, 2019, 05:15:46 pm
content: All thanks to your excellent photos!Velleman are a strange company. They seem to be one of the few electronics hobbyist companies left and their products seem to be mostly made in China but with the bonus that the products actually seem to try to follow European safety requirements. The extra insulation around all the high voltage wires, the correctly constructed earthing and various other things like ensuring there are no bare high voltage connections inside, etc. show that they have found some Chinese suppliers who are at least prepared to attempt to meet the safety requirements.What I wonder is if the premium price that they charge for a lot of the things they sell is actually worth it when places like Aliexpress and Banggood exist. Even if your purchase from Banggood gets hit by customs, it often works out cheaper than buying from a local retailer. Certainly, I only buy from my local Kjell & Co if I'm in a hurry as the prices they charge for many simple items are simply outrageous!When it comes to good bench power supplies, you should keep an eye out on eBay for the good old Thurlby PL320 as pictured below:You can generally pick them up for around the 100GBP mark and if they are still working after 30 years, they're likely to keep working as well.

author: blurpy
author_rank: Regular Contributor
timestamp: December 13, 2019, 07:13:55 am
content: Yes, I find Velleman to be a bit strange. The previous PSU they had was a rebranded Korad. This one is very difficult to find information about, but I bought it hoping that it would be acceptable quality and it would follow safety requirements. It's reassuring to hear that it seems to be true (with some minor issues). Most of the comments online about Velleman seems to be about their bad support. I actually asked them if it was possible to disable the sound and they replied the same thing people suggested in this thread. I expected them to give lots of warnings about warranty and safety hazards, but no. I contacted support on a different product but they never answered that one.I got it from Kjell & Co, and do think they are very expensive on a lot of things. As someone new to electronics it's hard to know the value of products, especially with all the rebranding going on. I've bought some cheap stuff from China, but nothing I can't afford to lose. It feels safer to have some place local to go. Looks like Kjell & Co sell a lot of noname Chinese products that they brand as their own. Hope they have quality control of the safety of the electronics.Thanks for the tip about the Thurlby PL320! I'll have a look at it.

author: blurpy
author_rank: Regular Contributor
timestamp: May 21, 2020, 08:37:47 am
content: Seems Tekpower has a version of this PSU as well, the TP3005P:https://tekpower.us/power-supply/linear-powersupply/tp3005p.htmlWith the exception of the terminals sticking out, and a carry handle, they look identical.Still don't know who the original manufacturer is though. I would guess Tekpower is also just a rebrand.