Ebay solder paste dispenser warning! - Page 1
Forum section: electronics / general

author: alexanderhiam
author_rank: Contributor
timestamp: September 14, 2013, 02:48:51 am
content: I spent a while recently looking at all my options for cheap Chinese solder paste dispensers, and I eventually settled on this one:http://www.ebay.com/itm/400537710815. I liked all the snazzy extras, plus the foot switch uses a very hackable standard 3.5mm audio jack. Oh yeah, and those decade switches are pretty darn snazzy!Anyways, I ordered their "110V version" two weeks ago and it arrived today. I was a little wary of this claimed 110V version, so the first thing I did was open it up. Not so surprisingly, someone between me and the manufacturer had replaced the transformer, and they simply cut the hot input from the power switch and directly soldered the 110V transformer lead to it. This joint was "insulated" with a small piece of very cheap electrical tape, which had already turned into a gooey mess and fallen off during shipping, leaving the exposed 110V solder joint hovering just above the metal chassis (see the attached photo). So watch out with these things!

author: AlfBaz
author_rank: Super Contributor
timestamp: September 14, 2013, 05:01:46 am
content: Quote from: wilfred on September 14, 2013, 04:46:53 amWith tongue firmly in cheek...

author: alexanderhiam
author_rank: Contributor
timestamp: September 14, 2013, 06:36:30 am
content: Oops, that was huge! It's now a more friendly size.

author: Dagon
author_rank: Regular Contributor
timestamp: September 14, 2013, 06:43:23 am
content: Beyond the horrible hack what's the build quality like?

author: AlfBaz
author_rank: Super Contributor
timestamp: September 14, 2013, 12:22:42 pm
content: ...and does it work ok?I often look at these cheap gizmo's as a good base to make something half decent

author: amyk
author_rank: Super Contributor
timestamp: September 14, 2013, 12:57:21 pm
content: Is the chassis grounded?

author: mrflibble
author_rank: Super Contributor
timestamp: September 14, 2013, 01:28:35 pm
content: Thanks for the warning! While looking for info on a dispenser like this, I came across a video with a similar issue:The price on those dispensers is very tempting these days... Lowest I found was in the $75 - $80 range on aliexpress. Decisions, decisions...

author: alank2
author_rank: Super Contributor
timestamp: September 14, 2013, 03:45:25 pm
content: Do you guys consider a dispenser a replacement for stenciling for low volume, or is it just best for one offs?

author: mrflibble
author_rank: Super Contributor
timestamp: September 14, 2013, 04:07:31 pm
content: I'm considering getting one for runs of say 1-3 boards for prototypes. Beyond that it probably makes more sense to use a stencil.

author: alexanderhiam
author_rank: Contributor
timestamp: September 14, 2013, 04:34:38 pm
content: The pneumatics and off-board electronics look identical to the 982. I was thinking they had swapped out the transformer, but when I took it out to resolder and heat shrink the bad joint I noticed a third primary tap that had been snipped off very close to the base of the transformer and left there, meaning even more bare mains potential wire! Good work guysSo I guess they just snipped one end of the primary and soldered onto the center tap. There's no 12V regulator, so they would have had to swap taps on the secondarry as well. Interestingly, the free secondary tap is nicely heat shrinked...Because the 983 has the decade switches and 7-segment display, they actually designed a board just for it (marked PCB-983), based on the Atmel AT89S51 (date code of the 18th week of 2012 fwiw). The very poor quality solder joints are all well crusted with flux, and I can see some oxidation in the DIP socket for the MCU. The AT89S51 seems like a pretty odd choice, but I guess it gave them a lot of IO for a pretty low price. There's a 7805 to power the logic and a TIP122 to drive the solenoid, neither of which are heatsinked. I watched their temperature while I rapidly engaged the solenoid for a couple minutes, and the 7805 raised 15°C above ambient and the TIP122 only 2°C, so no worries there.I actually got "free" DHL express shipping. I ordered it two weeks ago, but it was picked up in Hong Kong on the 12th, made it overseas and through customs, and arrived at my door in Vermont on the 13th (wow!!). If you figure the cost of shipping, I doubt the Ebay vendor spent more than $20 on it, which means very little cost to manufacture.@mrflibble I bought it for just that reason. I have to put together 1-2 prototypes at a time for work, so it seems silly to spend the money on stencils when I could get this for the cost of a few stencils. There's no denying that it's a total piece of junk, but because it's so simple all the problems are pretty manageable. I'd say it's worth the $80 from aliexpress, but I wouldn't recommend paying quite as much as I did.

author: alexanderhiam
author_rank: Contributor
timestamp: September 15, 2013, 05:19:14 am
content: Quote from: amyk on September 14, 2013, 12:57:21 pmIt is, so at least it probably won't kill you.Quote from: AlfBaz on September 14, 2013, 12:22:42 pmAfter two trips to two different hardware stores I had the right parts to adapt the hose fitting (which is pretty close to a standard 3/8" quick connect, just with an odd bevel), and it does in fact work. I don't have a suitable compressor yet, so I just tested it with a 5 gallon air tank I had filled to 80psi. I was able to paste a whole board twice over (just playing) and I still had plenty pressure left over. I was expecting much more leakage than that.Side note: I think this thing might use little enough air that it will work fine with just a 5 gallon tank and one of those cheap and quiet little tire inflaters. It uses so little air that you'd really only need to kick the compressor on for a couple minutes every few boards. That makes for a nice quiet solution for those of us who don't have a place for a big noisy compressor and/or work late into the night and have close neighbors.Quote from: AlfBaz on September 14, 2013, 12:22:42 pmI took the time to fish the PCB out, and it's even worse than I thought (see photos). It looks like it got wet at some point. I'm starting to think I should scrap the board and hack my own in there. I'll leave it for now though because I'm curious to see how long it will actually last.

author: sleemanj
author_rank: Super Contributor
timestamp: September 15, 2013, 05:32:58 am
content: Quote from: alexanderhiam on September 15, 2013, 05:19:14 amI think if you tun the vacuum retract up it would use air fairly quickly, if it's like the video above then it's an always running venturi.

author: alexanderhiam
author_rank: Contributor
timestamp: September 15, 2013, 05:36:18 am
content: Quote from: sleemanj on September 15, 2013, 05:32:58 amTrue, but if you need the vacuum your paste is probably too runny anyway.

author: peter.mitchell
author_rank: Super Contributor
timestamp: September 15, 2013, 08:11:44 am
content: Quote from: alexanderhiam on September 15, 2013, 05:19:14 amThat board looks pretty RS, I'd get another one made. If you use it infrequently, more so.

author: alexanderhiam
author_rank: Contributor
timestamp: September 15, 2013, 02:37:15 pm
content: Well, custom controller it is. Just taking the board out was enough to somehow kill the 7805, and if I replace that I'm sure the next cheap component will fail in no time. I'll post details once I get something up and running.

author: arvidj
author_rank: Contributor
timestamp: September 15, 2013, 03:09:12 pm
content: Quote from: alexanderhiam on September 15, 2013, 05:19:14 amIn case anyone is wondering, the air plug looks to be a '20PM' plug. It is not a common plug in the United States.Some of the universal couplers available in the US may actually work but it might just be quicker and more leak proof to cut it off and attach some flavor of the ubiquitous Milton plugs available at the big box store.

author: mrflibble
author_rank: Super Contributor
timestamp: September 15, 2013, 03:15:20 pm
content: Quote from: peter.mitchell on September 15, 2013, 08:11:44 amRS? Royally something? Note to self: when buying a dispenser like this one might end up making a new controller.Quote from: arvidj on September 15, 2013, 03:09:12 pmThat indeed looks to be the one used. Thanks, now I have a name for it.

author: alexanderhiam
author_rank: Contributor
timestamp: September 15, 2013, 03:22:03 pm
content: Ha! I figured out how the 7805 was fried. If you look at the picture of the MCU socket I previously posted, I followed the silkscreen for the smaller unpopulated DIP IC under it, which it turns out was backwards. I guess that was half me being dumb and half bad layout. Amazingly, when plugged back in the correct way, everything is still working fine.

author: robrenz
author_rank: Super Contributor
timestamp: September 15, 2013, 03:39:55 pm
content: I bought the exact same unit about 2 years ago.This threadhas some English instructions that may be helpful. My unit had the original silk screen markings on top removed but you could still see the halo of the markings. Same made in Taiwan model # etc etc. I just opened mine up to see if anything you mentioned applied to my unit but it was pristine as the pictures show. Very handy thing to have around. I use mine for dispensing grease and glue more often than solder paste

author: alank2
author_rank: Super Contributor
timestamp: September 15, 2013, 06:50:54 pm
content: Hi,What are the big differences between the 982 and 983 versions???Thanks,Alan

author: JoeyP
author_rank: Frequent Contributor
timestamp: September 15, 2013, 07:10:50 pm
content: Something else to watch for with chinese ebay paste dispensers: Mine (model marked KH228) came with an external wall-wort style step-down transformer. The unit itself was 220v but being advertised as 110v version.

author: robrenz
author_rank: Super Contributor
timestamp: September 15, 2013, 07:13:43 pm
content: AFIK the 982 is just analog pot setting of dispense time per cycle. The 982 has digital readout of the dispense time and digital setting of the dispense time and also digital setting of the interval between dispenses (if you have it in the proper mode). I only use two of the modes, Dispense while the foot pedal is depressed and one shot mode where each pedal press activates the dispense for the set time once per pedal press. The other modes have had no use to me in the two years I have used it. But the digital readout is nice because it holds the last duration of pedal press. That lets you visually dispense what you want then read what time that was and put that setting into the dispense time as a starting point for semi auto operation.

author: alank2
author_rank: Super Contributor
timestamp: September 15, 2013, 08:26:05 pm
content: Quote from: robrenz on September 15, 2013, 07:13:43 pmDo you think the 983 is worth more $$$ then?

author: robrenz
author_rank: Super Contributor
timestamp: September 15, 2013, 08:34:36 pm
content: Not really, often I don't even use the shot time at all. You can get the pressure just right and hold the pedal down continuously and hop from pad to pad and it is faster than on/off for each pad. Like many of us I got caught up in the "got to have all the bells and whistles" when I bought mine

author: David_AVD
author_rank: Super Contributor
timestamp: September 15, 2013, 09:51:57 pm
content: We have the analog version and use it for solder paste on small runs of boards as well as a vacuum source for the SMD placing operation.Overall it works well, but has developed an issue where it stops working and needs a power cycle to get it working again. Maybe there is a small micro in there that's locking up when the solenoid turns off sometimes. It's on the "to investigate' list. I have thought about making a replacement controller board for it.

author: peter.mitchell
author_rank: Super Contributor
timestamp: September 16, 2013, 06:39:42 am
content: Quote from: mrflibble on September 15, 2013, 03:15:20 pmhttp://australiandictionary.net/rs

author: amyk
author_rank: Super Contributor
timestamp: September 16, 2013, 11:30:04 am
content: Quote from: alexanderhiam on September 14, 2013, 04:34:38 pmIt's the cheapest for that amount of IO, and for some reason the Chinese seem to prefer 8051 a lot. The cheapest PIC with similar specs is roughly double the price, and AVRs several times more...

author: mrflibble
author_rank: Super Contributor
timestamp: September 16, 2013, 11:41:47 am
content: Quote from: peter.mitchell on September 16, 2013, 06:39:42 amThanks, wouldn't have guessed that one.

author: Hardcorefs
author_rank: Regular Contributor
timestamp: September 16, 2013, 01:19:39 pm
content: A bare wire would be the least of your worries.After 20 years of EXP. with Chinese manufacturers, any sort of transformered product is likely to be the kiss of death.From bare copper wire run through boat varnish to get insulated wire,to 'tightened' feeder equipment on bobbin winders.(it stretches the copper wire to save money, but fractures the varnish coating)In many cases of Chinese products you don't even get what you paid for.

author: robrenz
author_rank: Super Contributor
timestamp: September 16, 2013, 01:24:28 pm
content: Quote from: mrflibble on September 16, 2013, 11:41:47 amI thought it meant "Radio Shack" quality.

author: mrflibble
author_rank: Super Contributor
timestamp: September 16, 2013, 01:32:44 pm
content: Quote from: robrenz on September 16, 2013, 01:24:28 pmIsn't that what he just said?

author: metalphreak
author_rank: Frequent Contributor
timestamp: September 16, 2013, 02:05:29 pm
content: Yeah mine was fine (and still is). I think its the guys who mod them outside the factory with 110v transformers that cause the issues.Some (not many) of them also had the foot switch operating on mains voltageI think the majority of them now run the switch on the LV side.The digital shot timer seems almost like a wasted feature. It takes 5 seconds to get the setting right on my manual one and then its a piece of cake. You can even put it on continuous feed and just modulate the amount of paste with the foot pedal. Handy for all the different sized pads you might have.The terrible phone video belowshows how well I could do it after spending about 5mins using it.Honestly, I don't know why they even bother putting a transformer in these. An external switch mode plug pack would work just as well! You guys with 110V should just buy whatever is easiest to get, rip out the transformer, and put in a DC barrel socket on the back. Anything ~14V or higher like an old laptop charger will do (to feed internal 12V reg).Oh and the air-line plug that came with mine was the standard Nitto coupler type, which is pretty much the standard in Australia. New Zealander's tend to use ARO fittings AND Nitto, which makes it confusing. I believe the american's use the ARO style?

author: alank2
author_rank: Super Contributor
timestamp: October 02, 2013, 12:42:32 pm
content: For those of you who have one of these type units - what type of pressure do you have to use to run it?I've got my compressor around 90 psi, and I saw a youtube video showing a guy running 50 psi, but mine will not run this low. If I adjust it up to 80 or higher it will work. At 70 it barely does anything, at 60 psi it doesn't even make a noise.

author: David_AVD
author_rank: Super Contributor
timestamp: October 02, 2013, 10:45:42 pm
content: We have a regulator/trap (off the main line) that reduces the pressure to about 70 PSI into the unit. One the actual unit, the pressure is set in the 30 - 50 PSI range depending on the paste and dispenser.

author: alank2
author_rank: Super Contributor
timestamp: October 03, 2013, 12:00:49 am
content: Quote from: David_AVD on October 02, 2013, 10:45:42 pmHmmmm - that doesn't sound good for mine then. Below 70 psi it won't do anything. On the inside the part that lets controls the vacuum vents to the inside of the unit. Hmmmmmm - maybe I just figured it out. The unit is normally airtight when closed. I removed the mains AC plug creating a large hole where air can escape... Back to the drawing board I guess.Nope that isn't the problem - I made the units case like it was with no holes and nothing change.I connected up an air gauge to the end of a tube without the pusher inside to see what kind of psi I can measure. It is less than 10 psi when the unit is set to 90 psi. If I put my finger over the end I can hear the air going out inside the unit instead. It escapes through the vacuum needle... Any ideas on what I can do to fix it? I can take a picture if necessary.

author: alank2
author_rank: Super Contributor
timestamp: October 03, 2013, 01:00:05 am
content: Here are some pictures - from what I can tell a difference between real and the schematic is that the gauge is not inline, but comes out of a solenoid valve port - I am assuming it is connected to the port across from it which is the regulator output.If my air pressure from the compressor is 90psi (it has a gauge) and I turn up the regulator on the unit to 90psi, the gauge will read 90psi, but when I activate it, it will do a much smaller amount, maybe 5psi. Solenoid value does measure 12V across it when activated. Below 70psi on the regulator, nothing happens.

author: alank2
author_rank: Super Contributor
timestamp: October 03, 2013, 01:32:07 am
content: Well, the side of the solenoid says 19.2-26.4V so I don't think my 13VDC adapter is going to cut it... I'll replace it and see what happens.EDIT: That fixed it all right! I was trying to be kind to the 7812 and not over heat it, but the rectifier board is supposed to have 24VAC as its input. I have an 833mA 24VAC power adapter and despite that it puts out around 26VAC, it works perfectly. Maybe they don't pull too much current through the 7812 - I put a heat sink on it to help it out anyway.It now works down to 15psi and even lower and has plenty of power. 60 psi and I could feel the tube bulge slightly from the pressure!