Step-down transformer for Japanese video gear?

[thatskaz]

Hi All, I’m currently building my first digitizing workstation at home. I have a Sony SVO-5800 from Japan, which requires a 120v to 100v step-down transformer as I live in the US. A friend of mine knows I live in an older building and recommended I get a power conditioner as I may have unreliable power and so my investments would be safeguarded against any outages. I’ve been looking around and have started to settle on the Furman PL Plus. However, I’ve never used a power conditioner and transformer, much less together, is there anything I need to look out for in terms of the two devices compatibility? I assume I plug the power conditioner into the wall, then plug the transformer into the power conditioner, followed by the VHS deck, etc. I suppose I’m just worried because the power conditioner also mentioned being on the lookout for voltage that was too low and I’m worried it might try to spike it up to 120 again.

Apologies if this is a silly question, I’m newer to this so I appreciate any and all help. Thanks so much.

[aramkolt]

I personally wouldn't bother with a stepdown transformer - their outputs can vary quite a bit based on manufacturer and what your line voltage happens to be at the time. A Variac or autotransformer usually costs about the same and you can dial into the specific AC voltage you need. The only downside after that is making sure you don't bump the dial unintentionally while something is running. I got one of the more popular 120->100V stepdown transformers on Amazon and it still gave me about 110V. An improvement, sure, but disappointing if you're actually wanting to target 100V. You might even be able to find a used variac on facebook marketplace or similar. vintage ones are pretty cool, but they could sometimes use a cleaning.

The SVO-5800 is a nice machine, but it'll almost certainly need a recap if it has many hours on it. They almost always have leaking capacitors due to the power supply running pretty hot which you'll find out pretty quickly if you just put your hand near the power supply after it has been on for a while.

Power conditioner may or may not be helpful depending on how dirty your line voltage is. Isolation transformers tend to do better with some types of noise elimination, particularly ground loops. Whole thing is kind of a rabbit hole, but if you aren't hearing a high pitched whine in your audio or getting repeating/patterned noise in your video captures, you can probably get away without a power conditioner. If you want to see what the "cleanest possible" AC power looks like, you could run your setup from 12V LiFePO4 batteries and a pure sinewave inverter and if you notice zero difference between using that and your line voltage a power conditioner is likely overkill.

Bigger important thing is to have all of your capture chain connected to the same power strip or UPS as grabbing power from multiple wall outlets can cause ground loop issues.

[latreche34]

Better to get a UPS with voltage and frequency conversion capability.

[aramkolt]

Quote:

Originally Posted by latreche34

Better to get a UPS with voltage and frequency conversion capability.

For that to be possible, the UPS would need to do a similar charging of a battery and running an inverter continuously. A lot of UPSs don't make it very clear if they run that way - so you'd have to assume that most are not built that way. The term for those is apparently "Online Double-Conversion UPS" which makes sense, just never heard the term, probably because they are not common. Looks like most of those are at least $1000. I'd be less expensive to make your own from a pure sinewave inverter, a LiFePO4 battery and a battery charger that charges the battery at least as fast as you'll be draining it during use. Some portable power stations will allow you to change the voltage frequency output while they are operating on battery as well.

If you want to do the above, the opposite of an "online double conversion UPS" would be "Line Interactive" - so if the UPS says that in the description, it is not one of those.

The frequency conversion is the harder part, switching power supplies usually do not mind running on a different frequency because the voltage is almost immediately turned into DC and the rest of the power supply does not "see" the line input frequency. It shouldn't affect capacitor ratings of the main filter cap either because the formula for RMS voltage is not affected by the frequency of the AC voltage.

[mts1]

Why not to use Japanese UPS? Assuming it would handle 120v input.

[vwestlife]

Open it up and see if the power supply has an easy way to be changed to 120 volt input, such as by moving a soldered jumper on the circuit board the internal transformer is connected to.

[dpalomaki]

First, what does the nameplate on the machine say? Some SVO-5800s were rated for 100-120 VAC 50/60 Hz. (e.g., models exported to the US, Canada, and UK).

The service manual (if you can find one for the specific model you have) should show any voltage adjusting jumper positions.

Line voltage specs in the US tend to run on the order of 112 to 128 volts depending on time of day, other loads on the wiring and system, etc. a nominal 120 volts. A modest cost 120 to 100 volt step up/down transformer rated for at least 2x the gear power consumption (watts) plus a common surge protector should be all you need.

If your PCs, monitors, printers, TVs, etc. have run fine in your building to date that is a good sign. If the power is flaky than a UPS similar to one used for a PC might be in order. Put it ahead of the step down. Just be sure you have the needed wattage ratings.

[aramkolt]

Oddly, there is a lot of Japanese equipment that is just rated for 100V 50Hz, most consumer VCRs there as an example. Frequency really doesn't matter as mentioned before, 60Hz should be fine as it is immediately used to charge up a DC capacitor (the main filter cap) prior to switching that voltage rapidly (much higher frequency than 50/60Hz) into a small transformer that gives the various output voltages.

[un_kbron_del_664]

I have a Japanese SVO-5800, and I’ve been using it here in the US without a power transformer or anything of the sort. So far 0 problems! If this is going to have any consequences, please, someone let me know.

[aramkolt]

Hard to say, but I guess if you've been ok so far, could be possible that it is dual voltage and just not marked as such. If I was you, I'd at least look at the main filter cap to see what the voltage rating is on it. RMS voltage of 100VAC is around 141V whereas 120VAC is more like 170V. If the main filter cap happens to be rated for 150V or even 175V, you're asking for trouble. Probably better to have that be at least 200V rated. The other thing that might not be ideal to run on 120V would be the the startup/switching circuitry in the supply. It's hard to say if that's safe without knowing the component values of everything and measuring what voltage is running the ICs compared to what they are rated to handle.

For an expensive machine like that, I'd at least say it's worth using one of the step-down transformers or a variac. You'll notice Japanese sellers are quick to point out that their equipment is 100V and that's mainly to safeguard against the equipment blowing up unnecessarily.

There's a video here that explains switching power supplies fairly well, the pins of concern would be the VCC pin on the switching regulator and the main filter cap. The actual rating of the mosfet would be good to know as well to make sure it isn't switching voltages higher than what it is rated for.

https://www.youtube.com/watch?v=RcH57E1IG0U

[omar543421]

Just make sure the transformer is good quality and properly rated for the deck.