Cheap Ebay Stuff: the Good, the Bad, and the Ugly – Post Your Reviews

[Viperel]

Originally Posted by stj

if you need pata then you dont have much choice.

PATA to SATA convertor also works
https://www.aliexpress.com/item/1Pcs...757890047.html

even a SATA to PATA convertor
https://www.aliexpress.com/item/2x-N...544698809.html

[stj]

they dont work if you have no extra space.

[Per Hansson]

^^
This thing works really well:
http://www.ebay.com/itm/Delock-Conve...-/161060554286

[stj]

i'v seen those on DX for about $7, but i dont think those SSD's are cheap enough yet.
not for me anyway!

[momaka]

Here's one that I've been meaning to post for a while: a cheap AC light dimmer module. It is pretty simple, but can be useful for various projects. They used to sell for $5 on eBay about 5-7 years ago. Now you can find them for just a little over $2.

http://www.badcaps.net/forum/attachm...1&d=1500566435
http://www.badcaps.net/forum/attachm...1&d=1500566435
http://www.badcaps.net/forum/attachm...1&d=1500566435

Not sure if these dimmers can handle 2000 Watts, as the listings claim. But they are built reasonably well. I don't remember what mine had for its TRIAC originally. I think a 16 Amp device. (I got it for free, because a “tech” previously had tried to use it to power a 12V DC fan. More on that in another thread I have coming.) I installed a 16 Amp TRIAC in mine as the replacement: a BTA16-6CWG, to be exact, and it works fine. I was able to drive a 450 Watt heating element without issues.

What's not so good about these is they probably make quite a bit of noise on the line, as they chop off the AC wave rather than pulse-skip (which typically requires a controller of some sort to do that). So in that sense, they are pretty much like the rotary light dimmers that can be found in houses. And of course, their filtering is very crude - just a 100 Ohm resistor in series with a 0.1 uF film cap. But for what it’s worth, it works.

Here is its schematic:
http://www.badcaps.net/forum/attachm...1&d=1500566435
On it, R2 is the potentiometer with the knob, and it is 500 KOhms. R3 is the smaller blue potentiometer with the turn-screw knob, and it is 2 MOhms. R4 and C1 are the output RF/EMI filters I mentioned above.

Perhaps the most important thing I should note is that these modules typically come preset for 220/230V AC. So when used on 110/115/120V line, the light dimmer usually doesn't output anything until the knob on the main pot is turned almost to the middle position. As a result, this leaves very little turning room for adjusting the AC voltage output before the load receives full power.

So if you get one of these, you have to use the 2-MOhm turn-screw pot to fine-tune your dimmer for 120V operation. One way to do that is as follows:
1: Turn knob on dimmer pot to full OFF position (fully counter clock-wise).
2: Measure resistance between the two pins on the 2-MOhn turn-screw pot and note it down.
3: Turn the screw on the 2-MOhm pot so that it start decreasing. Try three to four full turns.
4: Connect the dimmer to a 40-100 Watt incandescent light bulb and plug into wall. Then turn the knob on the 500-KOhm pot towards the ON position. When adjusted properly, the bulb should start to glow barely when the knob is about ¼ to 1/3 of the way towards the ON position. Also, when the knob is turned to the OFF position, the bulb should completely turn off. I highly suggest using a multimeter to check the voltage output of the light dimmer when it is turned OFF, as you don’t want to have it partially OFF when it is in the full OFF position. If the above adjustments did not make the dimmer operate as stated, then repeat these steps as many times as needed.

That said, there is no particular resistance to aim for when adjusting the 2-MOhm pot, because the “start” resistance for the TRIAC will vary depending on the TRIAC you have in your module. Also, keep in mind that the 2-MOhm pot is in parallel with the 500-KOhm main pot, so any resistance readings will reflect the total equivalent resistance of the two.

Another thing worth mentioning is that although this light dimmer has four (4) screw terminals (two for input and two for output), you only need to use two of them – the two middle screw terminals. That is, only the Live (L) needs to be connected to the dimmer, with the input being (L), and the output (chopped sine wave) going to the load you want to control the voltage to. The main reason I don't like to connect both Live and Neutral on these dimmers is because of the proximity of the L and N to the TRIAC's metal heatsink. If careless, it is possible to have the Live and Neutral short to each other on the TRIACs heatsink. So it is just better to not connect the Neutral at all and wire it directly to the load you are driving.

Lastly… BE CAREFUL. The knob on the main pot is placed on a metal shaft. The body of the main pot itself is not connected to anything in the circuit… but it is in very close proximity to Live potentials. As such, a fault could make it Live as well. Thus, I suggest that whatever project you build with this dimmer, it should be grounded and fused – especially if it has a metal case.

[ChaosLegionnaire]

my next complaint isnt about cheap ebay stuff but rather the ugly side of things i seem to be experiencing more often on ebay.

i won a laptop but after paying for the item and after the seller shipped the item, the seller said the item had a password but told me the password to get past it. i then complained that the seller should have stated that in the listing before selling it!

then some time later in another listing, i won a video card but again after paying for the item and before the seller shipped the item, the seller informed me that he had tested the item before shipping but there appeared to be some noise coming from the fan so he included a second fan in the package in case the video card had a failing fan.

so thats two times sellers did a bait and switch shenannigan on the item after i paid for it. im starting to get pretty sick of this. the next time sellers try to pull shit like this, i am going to get tough with them and telling them to cancel the order!

[stj]

i rarely buy anything used anymore - just lots of chinese bits.

like these:
https://www.aliexpress.com/item/10-K...862870959.html
https://www.aliexpress.com/item/High...841019452.html
https://www.banggood.com/50PCS-11_52...r_warehouse=CN

[diif]

Originally Posted by stj

i rarely buy anything used anymore - just lots of chinese bits.

like these:
https://www.aliexpress.com/item/10-K...862870959.html
https://www.aliexpress.com/item/High...841019452.html
https://www.banggood.com/50PCS-11_52...r_warehouse=CN

All good bits, although they should double up on the smaller diameter hollow needles and remove the larger ones.

Big sale on Ali in 5 days.

[momaka]

A few months back, I got another cheap eBay “gadget” that I think is pretty useful to keep around: USB to stereo headphone/line out and microphone input (both with 3.5 mm jacks). There are actually two types of these adapters on eBay: one where the adapter, USB plug, and 3.5 mm jacks are all molded into one piece and the other where the adapter and 3.5 mm jacks are connected to the USB plug with a piece of wire to the USB plug. I got the latter, as I figured it’s sometimes easy to accidentally trip/pull on the headphones/microphone wires and thus possibly damage the USB port and/or USB plug of the adapter. Here’s how the adapter looks like:



Depending on which seller you buy these from, they will run you anywhere from $1 (with free shipping! ) to $3 or $4 with a few bucks for shipping if ordering from a “US seller” (yeah right! ). Not knowing how good/bad these are and what’s the likelihood I would get a DOA adapter, I decided to order two of them for the cheapest price possible. After $2.14 total ($1.07 per adapter with free shipping) and three weeks of waiting, I got the adapters in the mail. They arrived shipped in plain mail package with no padding, straight from China. But surprisingly, both adapters worked just fine.

Because I ordered two and both worked, this made me curious – what chips are inside these things. I popped one open to check it. Here’s a few pictures of that:
https://www.badcaps.net/forum/attach...1&d=1535923601
https://www.badcaps.net/forum/attach...1&d=1535923601
I guess there’s not that much inside: just a few SMD components and a COB. PCB has “PF002C” written on it on one side and “PC1__ __ v2.0” on the other with what’s likely a design date (?) of 2016-06-22. You can also see that the PCB has silkscreen and holes on it for directly soldering a male USB type-A port. So it’s quite possible there isn’t much of a difference between the cabled adapters like mine and the ones where everything is in one piece.

What I really like about these adapters is that there’s no driver CD required – the adapter installs the drivers automatically under Windows 2000/XP and Vista/7. And if the system does not have an audio device already running, this adapter automatically takes over as the default Windows audio device. So in just a few seconds, you can add an audio output to any PC with USB. I got these to use with my Compaq Presario v6000 laptop, which does not have a functioning XP driver for its audio (Vista and 7 only). Also have an AsRock 939Dual-SATA2 mobo that I use mostly for testing video cards. Its Southbridge has slowly been dying on me, first loosing the SATA/SATA2 ports, then the audio, and finally the LAN. The PCI ports also go through the SB and are sometimes flaky, so I keep all PCI hardware to a minimum. With that said, in rare cases I like to have sound on that rig, and so the USB-to-audio adapters above work great.

In terms of sound quality… the audio sounds normal and clear. But bass is clearly lacking with regular 24-32-Ohm headphones. Most likely, the series multi-layer ceramic caps on the line out (C8 and C9) are responsible for that. I didn’t measure their capacitance, but I imagine they are 4.7 uF caps at best, given their size. That said, I doubt upgrading these caps would improve the bass much, as the chip under the COB is also likely quite weak. I haven’t tested the adapter hooked to a proper amplifier yet, but I imagine the bass should improve quite a bit. Thus, if you get one of these adapters, I strongly suggest using it with some type of an amplifier. In any case, I still think it’s a worthwhile adapter to keep in your box. So this is probably one the better cheap eBay-China deals.

[lti]

I've had a few more cheap products that I can quickly review. I haven't actually used eBay in years, but these are available there.

The first is an IDE to SATA converter that takes M.2 SSDs.
https://www.ebay.com/itm/373670641143
First, the plastic housing is slightly larger than a standard 9.5mm thick hard drive (in every dimension, not just thickness), and the through-hole IDE connector will cause additional clearance problems die to the length of the pins sticking out the bottom (and covered with a useless strip of fabric tape). The mounting holes are not threaded, but the plastic is soft enough that M3 screws can be rammed in (in case it's going in something with unusual drive mounting). In the end, it works, but the JMicron ship has compatibility problems with some chipsets (mostly VIA) that cause poor performance and the sealed plastic housing does not allow the SSD to be properly cooled (see the first picture - this is with a 120GB ADATA SU650 SSD).

The second is a Bluetooth audio receiver that seems to be called the M18. It's a tiny and minimal PCB, and it actually works surprisingly well. RightMark Audio Analyzer only shows problems with noise (which it apparently doesn't measure reliably - in this case, the dynamic range plot doesn't show the usual -60dB 1kHz tone) and stereo separation. This was powered from 5V through an S-812C50AUA-C3ET2 LDO (not a very good part - this might be hurting performance) fed from six AAA batteries and connected directly to the line-in on my computer (47k ohm input impedance). Strangely, it has 10k ohm resistors in series with the outputs, so that needs to be considered when using this board. The biggest problem I have is the volume level of the power-on sound and the sound it makes when paired. They were louder than my test audio, but since this isn't one of the boards with a built-in amplifier and no volume control (relying on the paired device to control the volume), it isn't a major problem.

[redwire]

That schematic shows a big LC filter for power to the M18, so maybe it needs really smooth power. I haven't tried one of the little boards.

[eccerr0r]

Damn didn't see this post for 4 years.

Originally Posted by momaka

Not sure if these dimmers can handle 2000 Watts, as the listings claim.

*cough*
Well, assuming a typical medium TRIAC, I will have to say it can probably power a 1000W load on 120VAC. However, if the clearances are good enough, it probably can really do 2000W on 220VAC. I'm not sure replacing the TRIAC is sufficient to increase rating however.

Originally Posted by momaka

because a “tech” previously had tried to use it to power a 12V DC fan.

Oof... Yeah, that would be an epic fail indeed.

Originally Posted by momaka

The knob on the main pot is placed on a metal shaft. The body of the main pot itself is not connected to anything in the circuit… but it is in very close proximity to Live potentials. As such, a fault could make it Live as well. Thus, I suggest that whatever project you build with this dimmer, it should be grounded and fused – especially if it has a metal case.

Indeed, or at least a plastic knob is used. I think technically speaking with the plastic knob that completely covers the shaft, it would count as "double insulated" and pass UL requirements.

[lti]

Originally Posted by redwire

That schematic shows a big LC filter for power to the M18, so maybe it needs really smooth power. I haven't tried one of the little boards.

I feel like 100mH is a misprint, considering the size of an inductor in that value that can be used on a power supply. 100uH is more realistic.

I got three boards, so I'll try one powered from a 7805 some day. The S-812C caused weird effects in other audio circuits, like RMAA showing a huge bass boost.

[redwire]

It is likely a noisy voltage regulator the S-812C, or you need more capacitance on the 5V.
Any RF TX can draw high currents during the chirp and this adds noise to the 5V rail.
I would be putting 100-1000uF on the rail to see/hear the difference.

[redwire]

Multimeter probes - I got the SNAKOL (snakeoil) from Aliexpress. Needle tips, and fake UL approval for 1000V. There are four different versions:
SK-0010A (10A + PVC wire) USD $2.11 free shipping
SK-1010A (20A + PVC wire) USD $2.27 free shipping
SK-2010A (20A + PVC wire + Alligator clip add-on) USD $3.06 free shipping
SK-3010A (20A + silicone wire + Alligator clip add-on) USD $3.84 free shipping

I splurged on the top of the line SK-3010A silicone wire. But it's really thin, no way even 10A would not heat it up. Everything is low grade PVC - the probes flex and bend easily, alligator boots black one hard like a rock, banana sockets are flimsy and warped. The needles are huge and stick out way too much, some reviews say they wiggle loosely. Stock ANENG and others are better built.

So a low cost set of probes but a bit pointless - fine needle tips for SMT/auto connector probing but huge long probes and "20A" rating is silly.
SNAKEOIL not recommended quality-wise but price is good. I'm trying other Ali stores now.

[mockingbird]

Originally Posted by lti

The first is an IDE to SATA converter that takes M.2 SSDs.
https://www.ebay.com/itm/373670641143

I would have went about this differently... You're right about JMicron - it's not reliable at all. Someone whos more knowledgable once mentioned that it doesn't even follow the specifications properly...

What you can do is install a PCIe IDE card with a Marvell IC. Marvell is probably the best chip for IDE in terms of compatibility.

The M.2 form is irelevant as long as we're talking about a device with a SATA interface (protocol-wise, not physical -- in other words, not an NVME device).

You can then adapt it passively to the SATA port on the controller (assuming the PCIe IDE controller has a sata port - the Marvell one does).

[lti]

I put it in a laptop, so there's no way to add a SATA card.

[lti]

I just tried a second Bluetooth board. It isn't as loud as the first one (even though the resistors on the output are the same values), and the resistor in series with the status LED is open. I'll need to spend more time testing to compare power supply options.

Also, the on/off button don't work on either board (which doesn't seem useful to me anyway), and the first board was drawing 35mA when it wasn't paired. It also draws 8.7mA when paired, but without audio playing. The 20mA maximum current when playing audio is accurate.

[stj]

maybe 35ma because it is active scanning at full rf output?

[s675]

Originally Posted by redwire

Everything is low grade PVC - the probes flex and bend easily

I have some similar looking leads that came with a cheap-ish clamp meter. The quality doesn't actually seem too bad, but one of them snapped where the coloured dot is, at the end nearer to the tips. I suppose that there are a lot of lookalikes, with some being better built than others.


On the subject of cheap stuff, many years ago I bought some long VGA cables on eBay, from a same-country seller. After plugging one in, it didn't work unless wiggled a bit. I inspected it and saw that one of the pins had snapped off and was stuck in the receptacle. The pins were very brittle. I compared to a "proper" cable, where the pins just bent slightly when force was applied.

I've also heard stories of cheap PC PSU extension cables having high resistance connections and melting or catching fire.