10 Amp Variac Variable Transformer with Isolation, 1000va Max, 0~130 Volt Output

FIRST, This is an explanation for the "Quality Rating of 3" I gave it. As others have noted, it has excessive shaft "wobble" as delivered from the factory. I feel a '3' is a fair, perhaps slightly generous rating as I feel the 'wobble' would affect overall reliability in long term use.**IF THE FACTORY SHIPPED IT IN THE CONDITION IT IS AFTER THE MINOR MODS I MADE I, WOULD RATE IT A FULL '5 STARS'**!I've been "RadioActive" for over 60 years, starting when I was about 10 years old. So I have a LOT of electronics experience, both in my Professional Career and as a hobby.But this is REALLY about the Variac I bought, the good, the bad and the ugly!I needed both a Variac and an isolation transformer for my home workbench, but I don't have a large bench area. I really figured that 500va units would be more than large enough as I DON'T work on tube transmitters and such now-a-days. I can't man-handle them, not even a boatanchor like an R-390A receiver etc. But in doing a lot of research this was the ONLY unit I found that was an "Isolated" Variac. Reviews indicated that it is a TRUE ISOLATION transformer (backed up by my own tests).I read the reviews, both good and bad and decided to buy it anyway, figuring if it DID have problems I could fix it or return it.ONE of the things that repeatedly came up in reviews was a "wobbly shaft and excessive knob height". I figured I could probably take care of that IF mine had those bad 'features'. It did. . .********************************When it arrived I was a bit surprised, the unit is larger and HEAVIER than I expected (about 21 lbs). And like others said, it "STUNK" with a capital S. That doesn't bother me, a lot of the Chinese stuff I've bought stinks when first opened but it dissipates fairly quickly.********************************Examination showed that YES, it DID have a 'WOBBLY SHAFT'. After making sure that the unit was fine electrically, no sparks, or bad/bouncing readings when adjusting the Voltage (in other words, good contact between wiper and transformer windings) I then checked to make sure that it is truly an 'Isolated' Variac. IT IS, there is no continuity between the primary and secondary windings. ONLY the round ground pin from the AC line input is fed through to the outlet. This is a GOOD thing as it's a safety ground, but important.I used my DVM to compare the actual Voltage output against that which the analog meter showed. I checked it at both 50 & 110 Volts output. As close as I could read the small analog meter the readings were DEAD ON accurate. That was a surprise!NOTE: Some reviewers have said that the Voltage output doesn't correspond to the KNOB reading. DUH!! First, the arrow on the knob doesn't line up with '0' when it's turned all the way down. SECONDARILY, actual Voltage output will depend on what you put into it. Some people have NO CLUE. Use either the internal meter or external meter to determine the actual Voltage output. In fact I'm going to make a small interface box to go between the Variac and the DUT (Device Under Test) to easily measure both Voltage and Current draw of the DUT. . .********************************NOW TO SEE ABOUT FIXING THAT WOBBLE!Having determined the unit is working correctly, no obvious electrical problems, I pulled the knob and examined the "Wiper assembly" to see why it wobbled. The shaft goes all the way through the unit and is visible from the bottom. It appears to have a lower bearing that is OK.The "wiper" is on a husky piece of plastic (think it's white Nylon). There are two metal inserts on that plastic thingy, and two setscrews that are threaded into the metal inserts. NOT easy to get a screwdriver in to check their tightness.**************************************NOTE: DO THE FOLLOWING AT YOUR OWN RISK, BOTH FOR SAFETY AND 'RETURN-ABILITY' REASONS. ONCE YOU DO IT, IT'S LIKELY YOU'RE STUCK WITH IT AND WILL BE UNABLE TO RETURN IT!!!**************************************HERE'S HOW I FIXED THE SHAFT WOBBLE. . .1. I found that taking two screws out of the front panel that holds the meter, switch and outlet there is a nice large hole that allows access to the setscrews and upper shaft. I checked, one setscrew was loose, the other one not as tight to the shaft as it could have been.2. I loosened the second screw, pushed DOWN on the wiper assembly and tightened the set screws. This alone took a lot of the wobble out of the shaft. It still had a little bit as it doesn't have a true bearing at the top.3. Examination showed that I could probably make it better though. I found a round piece of Phenolic about 2.75 inches in diameter and 1/8 inch thick. I drilled a hole in the center and slid it down over the shaft. This was to act as a washer or "rubbing surface" for the knob (there are three screws in the top, under the knob that would otherwise rub).4. I then drilled the knob shaft hole ALL the way through the knob. This allowed pushing the knob further down the shaft so that it was actually lightly rubbing on the Phenolic washer. In this position the shaft protrudes out the top of the knob maybe 1/16th inch, perfectly tolerable!NOTE: The slight bit of shaft protruding above the knob IS NOT a safety issue as the shaft is grounded through the lower bearing to the case, which is grounded to the round ground pin on the power plug. BUT if you're concerned about it, glue a small plastic cap over the exposed shaft after installing the knob.5. Checked ALL my work, VOILA! Almost NO shaft wobble at all, it feels very good. Remounted the front meter panel with it's two screws. While it was off I checked the Chinese soldering, ALL soldering looked VERY good for Chinese workmanship (I'm used to having to rework the solder on some Chinese products I've bought)!6. I then checked to make SURE that there were no Voltage glitches or dropouts throughout the knob range, there weren't. The unit feels nice and smooth and functions as it should.***********************************AFTER DOING THESE MODS I RATE THE UNIT A 5+ AND AM VERY HAPPY WITH THE RESULTS. It's likely that this unit will last me the rest of my natural life with little or not problems.

I bought this PHC SC-10T variac to power equipment for testing with on oscilloscope. Without isolation, oscilloscope probing can be dangerous, as the BNC connector sheaths (thus, the probe ground references) are shorted to mains earth. What this means is that if your testing equipment is referenced to mains earth and you accidentally connect your ground probe (or your finger) to something other than mains earth, you have a short with the potential for massive current through your scope (or you). With isolation, the secondary side of the transformer floats, so long as the product does not include an internal mains earth connection to one of the sides of the secondary. A floating secondary can go a long way to protecting your equipment and you, since touching ONE probe (or finger; it can be done, but still don't do it!) to either side of the secondary will not cause a short, but rather just unfloat the secondary so that the potential of the probe (or finger) in contact is now defined as ground. One point of contact is OK with an isolated system, but once you define the ground, any other place you touch on the secondary will cause a short through the two points in contact, so you still need your wits about you. As always, your first line of defense for safety is always your brain and knowledge about what you're doing, not the equipment's safety features; those just help.Most basic variacs are NOT isolated, so I was surprised that this one claimed to be. Naturally, I was skeptical, so I emailed the manufacturer and asked for a wiring diagram of both the SC-10T and one of their non-isolated models. They responded within a couple hours with a schematic and spec sheet for both the SC-10T (isolated) and SC-20M (non-isolated). I was impressed with their speed and willingness to provide documentation. I'm sure they have to legally, but they made me feel like they were happy to provide it nonetheless. Impressive! The schematics do indicate that at the heart of the SC-10T is a galvanically isolated variable transformer, and the heart of the SC-20M is a non-isolated variable transformer. Upon receiving it, I immediately opened it to verify that the wiring was as shown in the schematic (any warranty is voided now, I know, but my life is worth at least a kajliion warranties). It was all as shown except that the fuse came after the switch and the schematic showed the fuse before the switch. That doesn't matter as much as the fact that they're both correctly on the high side of the primary. meh. With the variac unplugged, I checked continuity with my DMM between the input plug and the secondary outputs. The only things that are connected are the mains earth connections, but that was already shown in the schematic. What's very important to note here is that there was no continuity between either of the secondary connections and mains earth, indicating that the output should float if the mains earth connection isn't used. Also important is that the casing is all connected to mains earth. This is good, but once again keep in mind that, depending on how you reference the output, touching the tested equipment at the same time as the case of the variac could shock you.For your convenience, I've made a video demonstrating the isolation features of the SC-10T. I've chosen to give this product 5 stars for two reasons: 1. It is an incredibly affordable isolated variac for equipment testing, and 2.) customer service through the company is stellar. The build quality is only OK, but comparing the specs and safety features of this variac to what I expect out of this price range, I'm impressed enough to give it a relative rating of 5 stars. If you have an unlimited budget or are running an official lab, please buy a dedicated lab-grade variac or regulated high-voltage power supply. If, like me, you're using this at home for hobbyist use, I definitely recommend! After I finished filming I also tested the secondary side of the variac with my oscilloscope. I even attached an ammeter with a 25mA range to the ground probe of my scope so that I could see if there was even a tiny amount of current flowing through to mains earth. Nothing! Then I switched the two oscilloscope probes around and measured the other way. Zero! Waveforms looked nice and sinusoidal, with little-to-no shape change as the amplitude increased. This thing really works!*obligatory paranoid CYA statement: always know what you're doing with high voltages, and take this review as reference only. Always do your own testing. I am not responsible for your actions. Genuinely, though, be safe!*

I bought this isolation transformer after reading many reviews and also watching U-Tube video's showing a guy take one apart and what to watch for. I was a bit skeptical, but for the price I decided to give it a shot. It has exceeded my expectations and is one of the most important tools in my shop. It works fantastic, is very accurate and allows me the ability to slowly bring my restored vintage electronics up to voltage while monitoring my amp draw and voltage. The meter is a volt meter, but I built a custom volt/amp meter box that I plug into this transformer and then plug the electronics into my box. It works fantastic!

Product came as advertised. One other review had mentioned a bad smell. I would have to agree. Have some ventilation when you first use the unit. Left it in the shop overnight and the whole shop smelled like the variac. Hopefully over time the smell will dissipate. The shaft does have some play in the vertical axis but not bad. Dial reading doesn't correspond well with output voltage but if you want exact voltage use a meter. Can't beat having a variac and an isolation transformer in one. The 10T model is isolated on the secondary windings. Be aware though the third equipment plug on the receptacle is definitely mains equipment ground. If you are using a three prong plug and want isolation, use an adapter plug.

Works as expected. As other reviewers have noted, the knob does stick up about an inch away from the unit. The outlets on the unit could also use some reinforcing behind as they tend to push in a little bit when you plug something in. In the future, I may look at replacing the voltmeter with something digital to get a little bit of precision when I don't have a meter handy to measure the output.