Metcal STSS-002 (RFG-30) Repair - Page 1
Forum section: electronics / repair

author: paulywog
author_rank: Newbie
timestamp: April 21, 2020, 12:30:55 am
content: I recently decided to buy a used Metcal system on eBay since my old soldering iron's heating element died.Unfortunately, when receiving all of my parts, I found that the iron only gets mildly warm, certainly not hot enough to melt solder.I got several tips from two different sellers. I had the second seller fully test each tip before sending them, so I feel confident that they work.I also bought a used MX-RM3E handpiece. I don'tthinkit's bad, but it's the only part that I don't have a second of to test.It looks to be in good condition, with no imperfections I can see on the handle or coax, but the collet does have two broken prongs.Lastly I bought the STSS-002 base unit, and I now have two since the seller sent me another.My STSS-002s seem to be different from others that I've seen, mine only have a single red LED.This makes it difficult to tell if I'm tripping some intermittent/disconnected handle protection.Furthermore, I'm not positive that this station even has that, since information on the early Metcal models is not so prevalent.I'm hoping someone can help point me in the right direction for my next troubleshooting steps.All of the parts I bought were said to be "used, working" from eBay, so I'd like to get a replacement of the faulty part.Initially, I connected the handpiece/tip and measured the output to be a 30Vpp sine wave at the 13.5MHz.This seemed low compared to what I'd been reading, so I contacted the seller and he happily sent me another unit.Unfortunately, the new station has exactly the same output.Edit: I measured again, and am now seeing anywhere from 80Vpp when it first cold starts to 60Vpp when it settles down. Still no heat.I now need to question, is my handpiece somehow doing something to bring down the output, or am I simply unlucky and got two defective base units?I also measured the drain of Q2. I saw that the waveform (attached) matches what I seehere, but it's at a much lower amplitude of 30Vpp instead of 60Vpp.This is the same between both of my systems.What should my next move be? Is there more troubleshooting I can do?Should I ask the STSS-002 seller for another unit, or do I start to suspect the handpiece?

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: April 22, 2020, 08:31:42 am
content: I would suspect the handpiece, or more specifically, the co-ax. It is very common for the outer or the inner to fracture very near to the handle. From my experience the tip will still heat to some extent if the inner fails open circuit and the gap is very tiny. If you suspect the wand there is a lot of info on EEVblog about the RM3 and RM2 wands. The MX500 base has a small DC bias down the co-ax that the unit uses to detect if the co-ax/tip is present/open circuit. I don't think the RFG30 has this feature so the RM2 probably does not have the shunt resistor in the handle end.The RM2 wand will not work with the MX500 base because of this but I don't recall, without digging around, if the RM3 works with the RFG30. I have RM2 and RM3s if you need any readings.Regards, BT

author: paulywog
author_rank: Newbie
timestamp: April 22, 2020, 02:53:13 pm
content: Quote from: BurningTantalum on April 22, 2020, 08:31:42 amHmm, measuring with my multimeter, I get ~0.4ohms with the tip in the handpiece, and open line with the tip removed.I tried shaking around the coax at both ends, it did not seem to change.I wonder if there's an issue with the inductor or capacitor inside, but I suppose I won't be able to tell since I don't have an LCR meter.I may just need to bite the bullet and get another handpiece to test with while I'm still in the eBay refund window for my current one.At least then I'd have two full metcal units?In any case, thank you very much for your help!

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: April 24, 2020, 12:10:12 pm
content: Sorry, the resistor is in parallel with the capacitor and the pair are in series with the coil in the tip. I will measure the resistance tomorrow morning and post it. Also the tips have been known to fail with shorted turn(s) that reduces the heat output, although I have never come across this.The RG-30 and MX500 are not the easiest units to diagnose without a known good wand and tip.BT

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: April 25, 2020, 10:03:43 am
content: My working RM3E wand and lead measures 'open' without a tip, and about 3.5 ohms with a tip.BT

author: Dan_CA
author_rank: Contributor
timestamp: July 04, 2020, 01:11:28 am
content: I am making a wand patterned after the RM3E. I would appreciate if someone would make some measurements of the wand dimensions. Specifically the diameter at the tip end and the length from the tip end to the start of the strain relief. Also how far does a soldering tip protrude from the end? ThanksDan

author: paulywog
author_rank: Newbie
timestamp: July 04, 2020, 04:04:25 pm
content: First off, I should say that a new wand did in fact fix my problem, so that's nice.Dan, by "tip end" I believe you mean the grip end of the wand, correct? The soldering tips don't seem to all protrude the same distance, with one of mine measuring 42mm from that edge and another measuring 35mm. I have 17mm diameter at the end, tapering down to 12mm for a grip, and tapering back up to 14mm for the body of the wand. From the end of the wand to the start of the strain relief is 136.6mm.Keep in mind these measurements are taken by a computer engineer with a cheap Chinese plastic caliper, so take with a grain of salt if something seems off.

author: Dan_CA
author_rank: Contributor
timestamp: July 04, 2020, 06:31:50 pm
content: paulywog,Thanks for the quick reply. Your measurements will be very helpful. I will be posting what I have learned about my Metcal RFG-30 and the wand.Dan