Review: OK International PS-900 Soldering Station - Page 1
Forum section: electronics / general

author: TopherTheME
author_rank: Regular Contributor
timestamp: December 17, 2010, 08:08:59 pm
content: Disclaimer:I'm at home sick today with a terrible migraine so pardon me if me if the text in this review becomes incoherent at some points.Per Dave's and many others advice, I decided that I would put down a relatively sizable amount of cash on a good quality soldering iron and donate my $13 Tenma iron. I've been studying some of the budget high-end irons offered from Hakko, Pace, OKI, and Weller, and decided to go with the OKI PS-900 as I got a really good deal on it off ebay and I wanted something with more of a pencil feel/short neck. I've also put a lot of time on a MX-500P and its by far the best iron I've ever used.See model here:http://www.okinternational.com/product_soldering/ps_900First Impressions:The moment you open the box and pull the thing out, you know that you just bought a kick ass iron. Everything comes very well packed in a sort of OEM plain brown cardboard box. My iron came with the power supply, handle, coil assembly, stand w/sponge and brass loofah thing, silicon rubber pad thing, power cord, and manual. My iron also included a tip as well even though vendors say that it doesn't. I think the ebay seller that I bought it from probably threw it in there.Power Supply:The power supply resembles a black powder coated steal brick and could probably double as a weapon for bludgeoning someone. Its very solid and well built and appears to be very well sealed so you don't have to worry about dust getting in or spilling your beverage on it (it doesn't seem like an issue until it actually happens). Its very simple and rugged design. There's a power jack for the power cord, a jack for the iron, and an on-off button. I've come to really like this no frill design from using Metcals in the past. As long as the iron stays at a relatively constant temp, I see now reason for temperature or power adjustment and prefer not to ever fiddle with it. One other important thing to note, unlike the older Metcal's, the power supply is freaking enormous. Its actually quite compact, I think its smaller than the Pace ST70 and Weller WES51 even, and has a smaller footprint than the cradle itself.I managed to open up one side of the iron without breaking the warranty sticker. I could only open up the back side as I didn't have a long enough screwdriver to get the front cap off. The guts are pretty much what you would expect, a bunch of big capacitors and inductors. I'm sure theres a microcontroller in there somewhere but I couldn't get to it without a longer screwdriver.Handle/Iron:The iron itself is rather pornographic, but kinda big. Using it makes me file like a midget or perhaps a leprechaun. The handle is fairly comfortable, similar to other Metcal's, although it would be nice if it had a rubber or neoprene grip instead of the ribbed plastic. The handle/iron splits into two pieces with a simple push of a button. One piece is the handle with the silicone cord and the other is the coil assembly which provides power to the tips, similar to the Pace intelliheat iron style. The tips slide on and off the coil heater very easily. Nothing to unscrew and they don't need to be yanked really hard like some of the irons of this design.The tips seem to be of excellent quality as well. They don't seem to build up much oxidization at all and look like they will last a very long time. The more popular geometries are about $8 a piece from Allied. My one complaint about them is that they are rather big, diameter wise. Its not that big of a deal but I like the older Metcal style tips better that have a smaller diameter and are more of a pleasure to use for small SMD work.Cradle:The cradle is pretty nice. It appears to be made out of a molded/sintered metal and holds a big sponge and a brass loofah. It also holds three spare tips and provides an "auto-sleep" function which reduces the temp of the iron when not in use. I'm kind of confused by the big hole in the sponge though. I have no clue why it would have a hole in it. Maybe to fill it with water? I dunno.Performance:This thing is awesome. Like everything else with Metcal stamped on it, it heats up and is ready to go in about 5 seconds after you turn it on. I'm to lazy to measure it, but the soldering tip temp appears to remain constant for everything I've tried soldering so far. The majority of my projects are power related so soldering big inductors and large gauge wires has always been issue and had to be handled using my hot air station but I don't think I'll have those problems anymore. The thing is very comfortable to use and the handpiece puts your hand closer to the tip for better control over what you're heating. The fact that the tips seem to oxidize very slowly is a big plus too since they don't need to be constantly tinned like most cheapo irons.Summary:For the price tag of $250 retail and tip cost of $8-$10, the PS-900 is a dam good iron IMO. You get Metcal quality and performance at the price point of most professional budget level irons (Hakko FX-951, Pace ST70). I think the iron is a bit overkill for the average hobbyist and I'm not sure I still would have bought it at full retail price as I won't be using it on a daily basis. But, for a tool that I use probably more frequently than almost any other (except maybe a screwdriver), I think the price tag is warranted.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: December 17, 2010, 10:24:01 pm
content: I have the same iron with a small curved tip for SMTs. I agree, it's an awesome iron.

author: Wim_L
author_rank: Regular Contributor
timestamp: December 21, 2010, 11:50:06 pm
content: The central hole is mostly for making it easier to clean the tip when you have a big drop of solder hanging from it. You can just wipe it off into the hole without solder-coating the whole sponge. Of course you could simply shake it off onto something else that can stand the heat, I guess.

author: Unknown
author_rank: Unknown
timestamp: December 22, 2010, 03:40:52 pm
content: Great review TopherTheME despite the migraine! It looks like a great midrange iron. I wanted to ask, does it have any means of adjusting the power delivered to the tip, or a temperature setpoint? The switch? at the front is for on/off?

author: cybergibbons
author_rank: Frequent Contributor
timestamp: December 23, 2010, 12:08:41 am
content: I have the same iron and also really like it. I bought it after experience of using Metcals in a lab.The reason the tips are a bit more chunky than the higher end Metcals is that these use 470kHz rather than 13Mhz. I've still not got my head around the "SmartHeat" technology used however.You can get a slightly slimmer handpiece that uses another type of tip, but it's hard to come by, as are the tips.Alex - the tips themselves regulate the temperature, there is no temperature measurement or electronic feedback. You can buy three types of tip - low, normal and high (I think they call them T = temp sensitive, F = FR4/normal, C = ceramic). The power delivered by the tips is controlled simply by the size of the tip - a tiny conical tip can deliver less power than a huge chisel tip.The outcome is that you never feel you need to adjust the temperature - they really are good at regulating themselves very very quickly.I know people will disagree with this...

author: Unknown
author_rank: Unknown
timestamp: December 23, 2010, 12:14:19 am
content: I see, so the temperature is regulated at the tip using a thermostat or by equilibrium between heat from the heating element and heat loss?In this case a smaller tip would be hotter.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: December 23, 2010, 07:38:04 am
content: No, there is no thermostat as such. The tip itself regulates the temperature.As far as I can work out, the tip is normally ferromagnetic and has large hysteresis losses induced in it from the RF power source. Once it hits the Curie temp, it transitions to a parramagnetic material and the losses drop massively. The temperature then hovers around this point.It's just a simple materials based feedback mechanism. Because it is right in the tip of the iron, it's a very tight control and it you'll struggle to move the temperature up or down by more than a degree or so, unless you massively overload the iron.Power and temperature are very different. Again, this is guess work and based on the higher-end Metcals... the larger tips seem to be able to deliver more power than the smaller ones. I think this is down to the size of the material in which the heating can be induced. This has nothing to do with the temperature directly - as long as the tip can deliver enough power, the temperature will not move. It's typical that a large tip will be used for bigger soldering tasks and therefore need to deliver more power.You can actually buy a in-line power meter that shows how much power the iron is drawing at a given moment.Another nice thing about Metcal irons is that the stand has a powerful magnet in it. This saturates the material in the tip, lowering the temperature once it is in the stand and extending tip life.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 23, 2010, 11:30:10 am
content: Yes - that's pretty much it - the material 'automagically' absorbs however much energy is needed to maintain it at its curie temperature.The other aspect is that the heat is being generated within a lump of metal, which is welded to the metal of the tip, so you have extremely low thermal resistance between the heater, the temperature sensing and the tip - conventional irons typically have some ceramic or similar electrically insulating material in the way, so the heater and sensing are much less tightly coupled, leading to overshoot and undershoot when the tip loading changes.I sometimes find the magnet-in-stand thing annoying - although small tips heat up in about 5 seconds, larger ones can take long enough to be irritating - what would be nice is a mechanical switch on the stand that allows the magnet to be moved away when using larger tips.

author: djsb
author_rank: Super Contributor
timestamp: December 23, 2010, 03:45:55 pm
content: I've liberated an MX-500 from a cupboard at work and so far I'm enjoying using it. It's speeds up my work rate enormously. I've not used it on SMD parts yet as I need to get a stereo microscope set up. I've got a Pace MBT350 at home as it does hot air/desoldering/soldering the lot. Bought this just before I got the job at Brunel. Used it once so far. Such is Life.

author: jklasdf
author_rank: Regular Contributor
timestamp: January 08, 2011, 09:46:17 am
content: Quote from: TopherTheME on December 17, 2010, 08:08:59 pmI don't know about the ps-900, but on the hakko 936, the sponge cutout wicks water into the main sponge. See page 3 of the manual for the hakko 936:www.tequipment.net/pdf/Hakko/936e199809a.pdf

author: andyg
author_rank: Regular Contributor
timestamp: January 28, 2011, 12:11:38 pm
content: I have a used a Metcal MX500 and can say they perform well.But I do have a story to tell about this unit, that one need to be careful of.The power entry is from a IEC 3-pin cord (standard cord) into a EMC filter of some sort. One day when using it, perhaps the contacts was dirty at the connection it was intermittently losing its connection to earth via this point, as a result when the dodgy connection was created, 120V AC potential would be formed at the soldering tip. This would be floating to regular ground. I discovered this after experiencing an electric shock every time solder was fed into a joint while soldering. You can imagine what damage this could do if you were soldering an IC...Changing the cord fixed this problem. Although I haven't tried to reproduce it yet, I have just assumed it was cord. Testing tip to ground resistance showed open circuit when issue was present (with 120VAC at tip when powered on), replaced the cord the tip-to-ground resistance back to zero and no 120V at tip.Something to watch out for...

author: garboui
author_rank: Regular Contributor
timestamp: February 07, 2011, 02:56:12 am
content: Quote from: andyg on January 28, 2011, 12:11:38 pmGround connections are definitely something to watch out for. I dont mean to OT this thread but for a general safety related warning a faulty ground can be potentially fatal!One day at work i had a spectrum analyzer connected to a reference antenna. The other ground referenced components in the test setup were the DUT powered by a bench supply and the dev/interface board that was USB connected to a computer. While holding the antenna (touching the sma connector) i went to reposition the interface board grabbing it by the ground shield on the USB connector. I had felt that all too familiar bzzzzzzz through my fingertips. Instantly I know something was wring. Checking with a DMM the potential between the SA ground and the USB/Bench supply ground was ~85VAC. Long story short it was all because of a floating ground on the SA due to a faulty cord. From this point on I always verify ground potentials before handling equipment/DUT; I recommend everyone do so as well.

author: DaveW
author_rank: Frequent Contributor
timestamp: February 08, 2011, 07:41:10 pm
content: QuoteI bought one of these from Farnell and it also came with a tip in the box-rather pleasant surprise! An STV-CH24A if you're interested

author: Salas
author_rank: Frequent Contributor
timestamp: October 17, 2012, 12:58:16 am
content: Zombie thread wake up just to add that I got one from Farnell too for quite a few months now, came with the same free tip. After using it enough I am positive its a great mid-range iron. Its small PSU foot print, build quality, low cost tips quality, and no frills flawless performance I came to appreciate. The hole in the sponge is to toss SMD without banging the iron on the tray to get rid off or dragging along the sponge I believe by the way.