How to make a "split-rail" +6V/-6V power supply for an old Ikegami camera?  - Page 1
Forum section: electronics / projects

author: KylesDigitalLab
author_rank: Newbie
timestamp: June 03, 2025, 12:49:12 am
content: Hello, I am soon going to be purchasing a rare vintage Ikegami HL-77 3-tube video camera from 1978.The problem that I face is how to power it; it appears to use a "split-rail" power supply, with +6V and -6V and a virtual ground. Please excuse me as I am new to this concept and never have seen a device that takes a positive and negative voltage. It seems to take these voltages at a max of 3.5 amps and there's two 5A fuses on the camera, one for each rail.I have a Sony 4-pin XLR power supply that can output 12V at up to 5 amps, so I think I've got enough current. I'm wondering how I can take the +12 volts from the XLR supply and convert it into +6V and -6V, in an easy and cheap fashion.I am planning on buying one of these connector plugs for the XLR power supply I have and then soldering wires to it that go off to whatever circuit I need that converts the voltage to +6V/-6V, and then soldering it to a 7-pin female plug that mates with the camera's power connector:https://www.ebay.com/itm/391942672835I also want to be able to power the camera off a battery; I have a v-mount battery that can supply enough current, and it has d-tap output, so I have a d-tap to XLR adapter cable. So I just need to make a cable that converts 12V XLR to +6V/-6V using the 7-pin connector that the camera uses. I'm not sure what 7-pin connector is used on the camera but I do have a photo of it which is attached.Also attached is the original brochure for the camera (in Japanese, but you can use Google Translate like I did) and a specification sheet from 1977.Any help would be appreciated.

author: squadchannel
author_rank: Frequent Contributor
timestamp: June 03, 2025, 02:14:56 am
content: the simplest way is to use a transformer with a center tap to power it with AC.if you want to run it on batteries, you need to get a little creative.two completely independent batteries, you can do this by connecting them in series.want to do it with one battery, the same thing using two isolated DCDCs.if you want to do it the difficult way, a power supply for a split rail could be designed.

author: KylesDigitalLab
author_rank: Newbie
timestamp: June 03, 2025, 02:20:35 am
content: I thought it has to be DC? Wouldn't AC not work? I don't see why I can't just take the +12V DC from the XLR power supply and run it through a regulator or two to get +6V DC and -6V DC. Unless it's not actually DC? Again, I'm very confused for why they decided to use this design instead of just going with +12V DC, the RCA TK-76 camera from the same era used a 12 volt power input. From what I've read, it makes designing the op amp circuits easier. That's all I know.

author: ajb
author_rank: Super Contributor
timestamp: June 03, 2025, 03:09:03 am
content: Whether it needs to be AC or DC depends on the camera. Using a transformer with a center-tapped secondaryplus rectifiers/filter capsand optionally regulators would be one easy way to get +/-6V.The difficulty with trying to take a 12V supply and run it through a regulator or two is that most voltage regulators can only sink or source current. Whether you need to sink or source current into the 0V terminal depends on whether the positive or negative side of the camera circuitry draws more current, because the 0V terminal carries the difference between the two. If you know that the positive sidealwaysconsumes more current, then a standard negative regulator (like a 7906) will work fine. Conversely, if the negative side consumes more current, then a standard positive regulator (like a 7806) will work. If you don't know, or if the current balance shifts during operation, then neither one will really work. If the imbalance is relatively small, you can add some extra load (like a power resistor) to one side of the PSU to offset it, but that's pretty inefficient, and linear regulators like the 7806/7906 are inefficient to begin with.There are devices called "rail splitters" that can sink or source current, and are designed to do exactly what you want, but they are not as common these days, generally can only handle a relatively small imbalance current, and are no more efficient than the standard linear regulator option.Like squadchannel recommends, a pair of isolated DC-DC converters would be a good way to go. Since each would independently feed one side of the camera circuitry, the imbalance is no longer an issue. You also have the option of tying the camera's 0V to the main supply's ground, if that is important (like to ensure that any signal connections are ground referenced). You could also look for a single DC-DC converter with 12V in and +/-6V out, but you'll have more (and probably cheaper) choices with a pair of 12V to 6V converters. Even so, 3.5A (~23W) is relatively high for a 6V isolated converter, and 6V isn't a very common voltage, so they probably won't be all that cheap. You might want to look at 5V converters with output voltage adjustment and see if they can be tweaked high enough to work.

author: KylesDigitalLab
author_rank: Newbie
timestamp: June 03, 2025, 03:21:16 am
content: I've reached out to some people who are at the Museum of Broadcast Technology who may be able to help. They may be able to tell me if the positive or negative side draws more current or if they switch.So I can run it off the 12V XLR supply using two 12V to 6V isolated DC-DC converters? And I assume I can buy these off of DigiKey?I just need to get something into the camera to power it up to make sure it still works after 40+ years of sitting. Then I can work on probably designing a proper power supply for it since the original power supply is probably impossible to find. Ikegami is usually pretty reliable over many years so I don't think it will have much of an issue unless something catastrophic happened to it.

author: aeg
author_rank: Regular Contributor
timestamp: June 04, 2025, 01:36:55 am
content: Start off by powering it with a dual output bench supply. It's a good idea to own one of those anyway.

author: SteveThackery
author_rank: Super Contributor
timestamp: June 04, 2025, 10:44:34 am
content: Quote from: KylesDigitalLab on June 03, 2025, 03:21:16 amI think you mean something like this?It should work OK. Or, as @aeg says, a split-rail bench psu would be fine, and a useful addition to your workshop. Alternatively, get one of those 8-cell battery boxes for eight AA batteries (12V), and centre tap it by trapping a piece of wire under the spring between cells 4 and 5.If it were me, and I didn’t have a suitable bench psu, I would use AA cells just to check out the camera. AA cells always come in handy. Then use the isolated DC-DC converters for a more permanent solution. Don't forget the decoupling capacitors.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: June 04, 2025, 12:02:31 pm
content: I would buy two cheap plug-in power supplys eg Meanwell RS25-5 and stack them together. They are fitted with V Adj potentiometer - with some luck they could reach 6V. Input range between 88..264VAC. (Price in € act approx 8,50 each)And be cautious in connecting unknown Psu's & battery packs - housing is grounded to center. I've seen magic smoke from the first board (PSU) and the big black holes in caused by an unsuitable BP in a HL77. Thanks going to Ikegami-Tsushinki Neuss (Ger) for restoring that board :-). Yes, they did! (late '80).Setup & adjusting HL77, 79AtoD without SM, a couple of testcharts, suitable lighting and an Ulbricht-sphere is a nightmareEdit:p.S.: personally i would'nt buy any of these cameras without extender-board(s)!

author: ajb
author_rank: Super Contributor
timestamp: June 04, 2025, 06:59:23 pm
content: Quote from: KylesDigitalLab on June 03, 2025, 03:21:16 amYep -- but they may not have many options given the relatively unusual voltage/current requirement. If the camera will operate at closer to +/-5V you have a lot more options.Quote from: Uunoctium on June 04, 2025, 12:02:31 pmA lot of those only have +/-10% adjustment range, and OVP may kick in at the top end of that -- maybe 5.5V is enough for the cameraBut AC-DC adapters are definitely more common in this power/voltage range, so that's a good option to consider if battery operation isn't required.

author: eugene
author_rank: Frequent Contributor
timestamp: June 05, 2025, 03:12:47 pm
content: Do a web search on the keywords "buffered virtual ground".

author: Terry Bites
author_rank: Super Contributor
timestamp: June 05, 2025, 06:13:00 pm
content: Please stop calling rails splitters "virtual grounds" guys.

author: Terry Bites
author_rank: Super Contributor
timestamp: June 05, 2025, 06:43:06 pm
content: Its not likely to be a needed in the power supply. It will have +6/-6 and ground. A virtual ground is an electronics term.Rail spitters are fine as long as the "ground" of the 12V supply is isolated from the camera ground and mains ground. If not smoke may appear, why risk it.Better just make or buy one.Given the figure you've provided, it would be prudent make or buy a 60W (or2x30W) supply.You won't find many ready made 6V types.But there are afew possibilities eghttps://www.aliexpress.com/item/4000094955071.html?spm=a2g0o.productlist.main.14.4f8a23d2oUBhUo&algo_pvid=ce5d2a92-276a-4e89-b744-93e720984f82&algo_exp_id=ce5d2a92-276a-4e89-b744-93e720984f82-13&pdp_ext_f=%7B%22order%22%3A%2269%22%2C%22eval%22%3A%221%22%7D&pdp_npi=4%40dis%21GBP%219.18%218.79%21%21%2112.08%2111.57%21%402103890117491488441154076e0026%2110000006801487091%21sea%21UK%213100120370%21X&curPageLogUid=MyYEoDPSRmHr&utparam-url=scene%3Asearch%7Cquery_from%3AYou'd have to buy them before the dollar is worthless though.So make is not such a crazy idea.Buy some 5A LDO pcbs

author: Analog Kid
author_rank: Super Contributor
timestamp: June 05, 2025, 08:48:33 pm
content: I vote for Steve T.'s AA cell idea.8 AAs, 4 for +6V, 4 for -6V, w/"center tap". Cheap, reliable supply for testing.