Category: Repair

T-962 Reflow Oven Upgrades & Fixes | Voltlog #338

This is the famous T962 reflow oven coming from China, you might find it under a bunch of different brands, it’s available to order directly from China but also from a bunch of local distributors who are importing these ovens but in general they all have this list of problems which can be easily addressed for improving the performance as well as the safety aspects of operating one of these.

I got mine for about $180 shipped from Germany so there was no tax involved and it got here pretty quickly but you can probably find it for less if you are willing to wait a bit longer and get it from China. I used to run my own reflow oven based on a toaster oven but trust me, unless you invest in a really expensive toaster oven you’re not going to get the same performance as with one of these dedicated ovens. They’re not perfect as I’m gonna show next, they still have a bunch of problems but once we address those problems it becomes a decent oven with superior performance when compared to a toaster oven.

So let’s start with the paper tape insulation problem. This oven uses glass wool for insulation of the hot chamber and to seal that they used a combination of aluminium tape and paper tape, it really looks like the cheap painters tape. Now obviously the insides of this oven are gonna get hot and that paper tape is gonna start to burn and it will release fumes and a nasty smell. If you buy this oven and start using it right away without implementing this fix, you will need to vent that room most certainly. 

Luckily this is an easy fix, the only thing you need is kapton tape. The idea here is to equip yourself with a pair of gloves and place the oven on a table that you can wipe clean when you’re finished to avoid contamination with the fine particles released by the glass wool. It’s best if you have some genuine kapton tape because it will stick better and you will have to remove all of the paper tape and replace it with kapton tape. You might also find some pieces of rigid cardboard/paper like material in there, I wrapped those in some kapton tape as well for protection against the heat and inserted them back where they were. Your oven should look something like this when you’re done.

CH341A Programmer 3.3V Fix | Voltlog #318

Welcome to a new Voltlog, if you watched the previous mailbag video I showed getting this CH341 programmer tool for EEPROMS and FLASH chips and my viewers were quick to point out this actually has a design problem regarding the voltage levels it puts out. So it appears there is a 3.3V regulator on board for providing power to the eeprom or flash chip via the zif socket but the CH341 itself is running at 5V which means it outputs 5V signals on the SPI bus.

Someone has reverse engineered this little board and put together a schematic which clearly shows pin 28 VCC connected to 5V but I want to make sure nothing has changed and this still present. And checking with a multimeter, pin 28 is still connected to 5V USB.

Connecting a 3.3V rated part for programming might result in damaging that part. You might get lucky, you might have a chip that will tolerate that but in general that’s bad practice and so we’re going to attempt to fix it by simply cutting the 5V line going into the CH341 pin 28 and supplying it with 3.3V from the onboard regulator instead. And the datasheet also specifies that V3 pin 9 should be connected to VCC and 3.3V as well.

The Curious Case Of A Very Sensitive PIR Light | Voltlog #315

This is a portable PIR activated LED light, it ships with some double sided adhesive backing and it’s pretty convenient to use around the house or when going camping I quite like it. It works with 4 AAA batteries and personally I use this inside a wardrobe to help me find stuff. If positioned correctly it turns on as soon as I open the wardrobe door. Because I like it so much I decided to order another one to place in a different closet for the same purpose. I don’t know if I ordered from the same seller, probably not, I just went on Aliexpress, did a quick search and ordered another one.

And here it is, after a long wait it finally arrived, at first sight they look identical, apart from a minor difference in the LED output color but that’s to be expected because whatever they can find at the market that particular day right?  But in practice I also noticed something different, the new one is much more sensitive in picking up movement, to the point where it turns on even if it’s behind a closet wall and I walk past by, or even behind a wall. I know it doesn’t make much sense, because these are supposed to be infrared sensors so they can’t pass through walls. But it must be bouncing the IR rays off the walls and it’s so sensitive that it is picking up those reflections, I would have no other explanation for this but if you do, let me know in the comments.

Identifying & Replacing A Fake FTDI FT232R Chip | Voltlog #314

Lately I’ve been getting a few of these serial interfaces from aliexpress, this is just a RS232 to TTL level converter while this one is a USB to RS485 interface and it’s great that we can buy these for cheap for we are getting exactly that, something cheap. This converter chip is likely not of the best quality and not to mention this FT232 chip is certainly not a genuine one. 

There is nothing worse than having to deal with communication issues and debugging your tools instead of the actual project you are working on so I’ve decided to replace these chips with some genuine, good parts because the pcb and the rest of the circuit should be fine as long as we have a good conversion chip in there.

You might be wondering if there is any way to tell for sure that you’ve got an FTDI FT232R clone. There are at least 2 methods that I know you can use. First one is to install an older version of the driver which FTDI released in 2014, after plugging your fake FTDI depending on the driver version it will either disable the FT232 chip by writing something to it’s internal EEPROM or it will modify it so that it shows a custom alert message over serial instead of your actual data. I don’t like this method, because there is a better, simpler way, you can simply check for the serial number of the FT232 which you can get from the device manager under windows or by using the FT_Prog utility. If your serial number is A50285BI or 00000000 then you most certainly have a fake chip because that is a popular serial number which is written to fake chips. They don’t bother changing the serial number on the fakes, they mostly write the same number or set it to zero.

Kunkin KP184 Electronic Load Issues Fixed | Voltlog #302

In this video I’m going to address the issues I found with the Kunkin KP184 electronic load during the review and teardown of the unit but also some issues people mentioned in the comments. There are 7 things I would like to address in total:

  1. Binding post internal diameter issue.
  2. Grounding issue with blue metal enclosure.
  3. Bad solder joints on thick wires coming to mainboard.
  4. IRFP250M mosfet safe operating area, fake or genuine?
  5. Supposed bug in tripping over-power protection.
  6. Supposed noise in constant current mode loop.
  7. Calibration procedure.

Nothing changes in terms of this being the best electronic load you can buy in this price range, II like it and I highly recommend it if you need to test power supplies or batteries, I think you will be pleased with this unit. If you would like to see the review or the teardown video I will link those on screen right now so you just have to click somewhere in this area. As always thank you for watching and don’t forget you can support this channel on Patreon.

 

Voltlog #252 – How to fix a solder bridge

Welcome to a new Voltlog, today I want to talk about solder bridges and show you how to deal with them. A solder bridge can happen for many reasons, incorrect soldering temperature, incorrect amount of solder being used, too little or no flux, or just the incorrect technique for soldering but they all basically mean the same thing , a blob of solder shorting two or more conductive surfaces on your PCB.

Modern printed circuit boards which typically get soldermask coverage even between IC pins will help prevent this problem because molten solder normally doesn’t stick to the soldermask surface and so it’s harder to form a bridge across that surface.

But even with enough experience and the proper technique solder bridges can still happen if you do hand soldering on fine pitch ICs, it’s just part of the soldering job. It’s true that as you get better at soldering they will happen less often but don’t think they go away forever. So it’s good to know how to deal with them.

Voltlog #173 – µAmp Current Source

Welcome to a new voltlog, today we are taking a look at a very interesting item that was sent in by a viewer of the channel. Fabian who is from Romania sent me this microAmp current source that he designed and built himself. Even though he built only a few units by hand it looks professional and you must have noticed the resemblance with the uCurrent built by Dave from eevblog, but that gadget is used to measure small currents while this one is used to generate small currents.

Link to the uAmp Current Source on Tindie

 

Voltlog #140 – ISDT Q6 Plus Lipo Charger Repair

Welcome to a new Voltlog, this will be a repair video, because my ISDT Q6 Plus battery charger has failed. If you remember Voltlog #109 I did a review of this charger and I’ve been using it quite often since I got it, with no issues whatsoever, until a few days ago, I think I was just storage charging some batteries, I did 2 batteries and when it was time for the 3rd battery to go on it would not start anymore, it was saying, “current operation is not supported”.

Get the ISDT Q6 Plus here:

Voltlog #137 – Eachine EV100 Distortion Problem Fix

In this video I show you how to fix the EV100 distortion or gray line problem. The problem is caused by an internal ac coupling capacitor which should be of a higher value to decouple any dc voltage offset from the video signal. While some people report a gray line plus some distortions I was seeing a black spot on the left plus some distortions.

I used a 220uF B sized tantalum capacitor and it worked great. But you can use anything above 100uF, electrolytic, ceramic, tantalum, whatever you have around. The voltage rating doesn’t matter as much, anything above 3V is good.

Something like an electrolytic might be easier to solder because of the longer leads that can be bent into the required spot, it’s really up to you what type of capacitor to use in this fix. There is enough room inside to fit any type of capacitor.

Here are some links where you can get the capacitors and extra info: