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| Metcal STSS-001 RFG-30 Disassembly and Measurements |
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| Dan_CA:
While cleaning up my piled high workbench, I came across a Metcal soldering station power supply that has been a sitting there for years. I also have some of the tips, but no wand. I decided to see if I could put together a working soldering station. Since I found some good Metcal information on this forum, I have decided to post my experience here to hopefully help others. To dispel any suspense, the unit I have is working, but connecting up a tip was trickier than I thought. I reverse engineered some of the circuitry and took a lot of pictures and waveform measurements and I will be posting what I have. The power supply unit is old. The date on the FCC ID application is 1986, which is the same year as the primary patent. The identification tag says Power Unit RFG-30 for Soldering System STSS-001. I have found pictures of Power Unit RFG-30 for Soldering System STSS-002 and they are not the same externally. Of course I don’t know if the internals are different. I will start with some pictures of the opened up unit as soon as I figure out how to add pictures. |
| Dan_CA:
An attempt to add a photo. The ID tag of the power unit. It slides in grooves in the back side of the case. |
| Dan_CA:
OK. I'm getting the hang of using this forum. I'll add some more photos of the RFG-30 that I have been working on. The case has been opened up and the strips have been removed to show what is under them. Note that the green LED is my doing to replace the small incandescent bulb that was burned out. It will have to be changed to a white LED to illuminate the Metcal logo. The 3 nuts on the left case side fasten the Power Supply Board to the case. On the right case side 2 nuts hold the IRF130 against a mica insulator. The top nut has an insulator behind it because the stud is grounded. The bottom nut has no insulator because the stud is the FET drain connection. The other nut holds the driver FET against the heatsink with a mica washer. The nut holding the RF connector to the case must also be removed to release the RF Board. Here are the insides of the separated case with the beautiful torroid transformer and two boards. I call them the Power Supply Board and the RF Board |
| Dan_CA:
Some more information and pictures today. Detail picture of the Power Supply Board. The red and grey wires at the bottom are from the torroid power transformer secondaries. Note that the two 1.6K resistors and the white wire at the top are my doing to replace the incandescent bulb with an LED. The SG3526 IC is the controller for a buck switching converter that controls the power to soldering tip. The round heatsink at the upper left is on a ZTX749 transistor which is the switch for the buck regulator. The buck regulator inductor is to it's right. The pot labeled VR1 is in the feedback loop of the buck regulator and sets the power delivered to the soldering tip at idle. I will soon post a schematic of this board. Next is a detail picture of the RF Board. To remove the board remove the 2 nuts holding the IRF130 FET and remove it (messy heat sink compound). Be careful of the little insulator under one of the nuts. The other small nut holds the VN67AF (TO-202 package) driver FET on the back of the board. There is also an insulator under the nut. Finally the nut on the type F output connector is removed and the board comes free. The round heatsink on the left above the 13.560 MHz crystal is on the 2N3553 oscillator transistor. The VN67AF is at the top middle under the blue pot. The little red auxiliary board is interesting and I will have more information about it later. The final picture is the back of the RF board. The VN67AF driver FET is at the top. The mica insulator sheet was left on the heatsink. You can also see where the IRF130 pins plug into the board. |
| Dan_CA:
OK here is the schematic that I traced out for the RFG-30 Power Supply Board. I think it could be of some use for troubleshooting. The component reference designators on the schematic match those on the board. I included component values that I could determine without disassembly. I drew the schematic using LTspice which I use all the time for circuit analysis. Of course this schematic has nonfunctional symbols so is of no use for simulation. RFG-30 Power Supply Board Final.pdf (66.83 kB - downloaded 338 times.) Following is my description of the Power Supply Board circuitry: DC power is provided by a torroidal power transformer and rectifiers using conventional circuits. The highest voltage and current supply, voltage V1, is provided by the two secondaries in series feeding a bridge rectifier. V1 provides power to the drain of the IRF130 power amplifier FET on the RF board. Additionally there are two half wave rectifiers fed from the center connection of the transformer secondaries providing lower voltages. V2 supplies the input to the buck regulator switching transistor. The regulated voltage, V4, then supplies power to the 13.56 MHz oscillator and driver FET on the RF board. V3 supplies power to the incandescent front panel lamp and the SG3526 regulating pulse width modulator which controls the buck regulator. As can be seen from the board connector, the only voltages supplied to the RF board are V1 and V4. |
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