Identify giant transformer from 1978 tape reel - Page 1
Forum section: electronics / beginners

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 02, 2019, 06:25:05 pm
content: 1st side2x red2x orange1x yellow1x white1x blueSecond Side2x green1x purple1x gray1x brown1x black

author: MarkF
author_rank: Super Contributor
timestamp: May 02, 2019, 08:01:42 pm
content: I too had a transformer that I could not identify.I started by measuring the resistance of each coil. At which point you can identify each coil and whether you have any center tapped windings. From the resistance you can probably guess which are the primary and which are the secondaries. I suspect that you have a dual primary and multiple secondaries. After I identified the primaries, I plugged mine in and measured the voltage on each secondary.When you plug it in, you will want to limit the current. Something like a light bulb in series.If you do this, use an old incandescent light bulb. None of the new fluorescent or LED bulbs.

author: Jwillis
author_rank: Super Contributor
timestamp: May 02, 2019, 08:04:26 pm
content: Transformer winding configurations can vary so much it would take a library just to catalog then all.Many transformers have multiple voltage configurations at the primary that are not limited to the standard 120VAC and 240VAC. It' very much dependent on application .For example ,a UPS transformer I have has 80VAC ,100VAC ,120VAC and 130VAC with a 15-0-15 and 20v secondary..By switching the primary the voltages at the secondary can be changed for the bulk ,saturation and float charge of the batteries .These multiple primary transformers are also in a lot of car battery chargers that set the output voltage and amperage for trickle charging ,fast charge and starter boost by switching the primaries.Some multiple Primary transformers are set up for various countries.In a lot of cases its just more practical to put secondaries on the same side as the Mains primaries.But for safety sake don't arbitrarily plug high voltage in without knowing which is what .Use a multi meter to find which wires have continuity with each other and draw up a schematic .Then use a know transformer with a low voltage of say around 24VAC as a power supply.Then you can measure voltage and document your findings.This will show ratios between the primaries and secondary winding s then just do a little math to find the potential voltage of each .

author: Jwillis
author_rank: Super Contributor
timestamp: May 02, 2019, 08:12:51 pm
content: The biggest problem with using a lamp to find how a transformer is configured is that the light draws current and some winding s on the transformer may not handle that current and could potentially burn up the winding s . The safest way is to use low voltage AC instead and measure with a multimeter .

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 02, 2019, 08:24:08 pm
content: I had a TEAC reel to reel tape recorder, which had an autotransformer multi-tapped primary. The reason being that the spool motors were fed different voltages depending on its actual function:1-During play or record, the take up spool motor would receive about 75% voltage, and the supply spool motor about 40% voltage, to maintain tape tension across the heads. The tape speed was of course, regulated by a synchronous capstan motor.2- During fast forward or rewind, the take up spool motor (could be either side) would receive full line voltage, whereas the other motor would receive about 25% voltage, again to maintain some lower value tape tension.Of course, you had the multiple secondaries to supply the required electronic voltages. You do not mention whether this tape machine was tubed or transistorized. If tubed, a pair of secondary wires (green-???) were the heater voltages and the remaining could be different V+ voltages.But again, all of this is speculation. Proceed with the valuable advice from the previous posters.The *incandescent* bulb in series is a good trick to prevent a severe short circuit. If it lights very dimly, you are fine. OTOH, if it lights brightly, you are overloading that winding. I have used 25 or 40 watt bulbs for that purpose.

author: Vtile
author_rank: Super Contributor
timestamp: May 02, 2019, 08:49:48 pm
content: If you can fit the transformer to your lab it is not a giant.

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 02, 2019, 09:34:39 pm
content: I will use as a door stop, its safer!!

author: Jwillis
author_rank: Super Contributor
timestamp: May 02, 2019, 09:43:45 pm
content: Ah wheres your sense of adventure.Anyone of us can walk you through identifying the winding s . 24VAC isn't that dangerous.Besides you might trip over your new door stop and break a toe.Edit : If you know the make and model of the tape player/recorder maybe we can find a schematic .

author: newbrain
author_rank: Super Contributor
timestamp: May 02, 2019, 09:54:06 pm
content: OK, completely OT (but good advice has been already given):I opened the thread thinking it was about transformers distributed in an SMT tape reel...and wondering how "giant" they could be.Time for bed.

author: MarkF
author_rank: Super Contributor
timestamp: May 03, 2019, 12:31:13 am
content: Yes, there is no danger/risk in just checking the resistance of each winding with your multimeter.If you find out how many windings (if any are center tapped or have multiple taps) and their resistances, we may be able to guide you through the rest of it before you apply any power.

author: bjbb
author_rank: Contributor
timestamp: May 03, 2019, 12:35:00 am
content: "Ah wheres your sense of adventure.Anyone of us can walk you through identifying the winding s . 24VAC isn't that dangerous."More than hazardous voltage levels, there are also hazardous current, power, and energy levels that are defined in numerous standards. For yourself, Canada has CSA No. 223, and for the U.S. there is ANSI/UL1310. And I forget what is the NOM equivalent for Mexico. Everyone else has to use the standards scoped for the particular type of component or equipment.Note that the the concept of a Class 2 power source is particular to North America, as no one else has fine taste in well-behaved electrons that are found in North America.

author: MarkF
author_rank: Super Contributor
timestamp: May 03, 2019, 12:41:52 am
content: Quote from: bjbb on May 03, 2019, 12:35:00 amI myself tend to plug the device into a long extension cord, stand far back, flip the switch and watch for the magic smoke from the "well-behaved" electrons.

author: mikerj
author_rank: Super Contributor
timestamp: May 03, 2019, 09:22:09 am
content: Quote from: Jwillis on May 02, 2019, 08:12:51 pmThe point of using a lamp is to wire it in series tolimitthe current, not to draw current.

author: Brumby
author_rank: Unknown
timestamp: May 03, 2019, 09:24:51 am
content: Quote from: queennikki1972 on May 02, 2019, 09:34:39 pmWatch out. It might be a toe-eater.

author: macboy
author_rank: Super Contributor
timestamp: May 03, 2019, 11:52:44 am
content: Quote from: Jwillis on May 02, 2019, 08:12:51 pmThe lamp is placed in series with the primary and the line voltage, not used to load the secondary.A 60 Watt incandescent lamp will draw only 60 W when plugged directly across mains of rated voltage. Therefore theseriescombination of the lamp and transformer can't draw more than 60 W, as the two impedances in series will be higher than either one alone. This limits the steady state fault current to at worst 0.5 A (120 V like North America) or 0.25 A (for 240 V like Europe).If you make a mistake and connect the mains across a low voltage secondary, or connect a 120 V primary to 240 V, it is very likely that the transformer will saturate, causing very high current to flow (this is the result of the inductance dropping due to saturation). The lamp limits this current. The lamp is unlikely to light up visibly if there no fault, since the magnetizing current of the transformer will be too low to cause it to glow. If it glows, you have a problem, but not one that will blow fuses or worse.When using the series lamp, make sure the measure the voltage directly at the primary coil rather than assuming it is at line voltage. Some voltage will be dropped by the lamp. Account for this drop when calculating the secondary voltages. E.g. If the secondary measures 20 V with 200 V measured at the primary, then it will be 24 V with 240 V at the primary.Note that the lamp helps protect the DUT (the transformer),not you. You still need to take all necessary precautions when working with high voltages (> 50 V or so) or anything capable of delivering high currents. The AC line is both.

author: Jwillis
author_rank: Super Contributor
timestamp: May 03, 2019, 11:55:06 am
content: Quote from: mikerj on May 03, 2019, 09:22:09 amA 100w incandescent light bulb has around 140 ohms resistance with a hot filament . At 120V will draw 0.85 amps which is more than enough to exceed the current rating wire 22 AWG and higher .A 40W bulb has a hot resistance of around 360 Ohms which gives around 0.3 amps which is enough to exceed the current rating of 34 AWG and higher.If a lamp is used , keep the test duration's short .Using a lower voltage is just an alternate method of determining the properties of an unknown transformer without concern of damaging anything or handling high AC voltage.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 03, 2019, 01:06:58 pm
content: One of the most basic exercises in exploring a mystery transformer is to create a grid to record resistance measurements between each wire and every other wire.Then you will see how many windings, whether they are tapped, and their relative resistance compared to each other. Without something like that to start from, you are wandering around in total darkness.

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 03, 2019, 05:57:08 pm
content: Model was Pioneer RT707 if anyone can find a schematic with the transformer on it.. I wouldnt even begin to know where to look.transformer is RTT-118

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 03, 2019, 06:07:02 pm
content: The very first hit on Google yields the first-class service manual PDF download:https://www.esotericsound.com/SalesImages/rt-707sm.pdfAnd if you look in the lower right corner of page 61, will see the transformer with all the wire colors identified.Google is your friend.

author: MarkF
author_rank: Super Contributor
timestamp: May 03, 2019, 10:48:16 pm
content: Close. Hers has two extra wires (purple and black).Maybe two primaries for 120V or 240V operation?pg.59 says power transformer part no. RTT-115

author: MarkF
author_rank: Super Contributor
timestamp: May 03, 2019, 11:32:42 pm
content: Getting closer. Only missing brown wire.https://elektrotanya.com/pioneer_rt-701_rt-707_art2540_additional.pdf/download.html#dl

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 03, 2019, 11:52:43 pm
content: It is trivial to measure the other two wires. As suggested by @MarkF, chances are excellent that they are primary (input) voltage taps for different international mains voltages. In any case, the info for the secondary (output) windings seems quite reliable.

author: MarkF
author_rank: Super Contributor
timestamp: May 04, 2019, 02:50:01 am
content: I believe the primary is one of two configurations.You will need to put the multimeter on the four wires to see if there are two windings or one winding with two center taps.

author: ArthurDent
author_rank: Super Contributor
timestamp: May 04, 2019, 04:53:02 am
content: MarkF -QuoteThere is one other possibility but not as likely. If you ring out the wires and find one that doesn't seem to be connected to any other winding, it could be an electrostatic shield between primary and secondaries. Some times the shield is brought out as a separate lead although the shield lead is often just connected to the metal core.One big advantage of finding the 2 manuals with schematics is that you might have a better idea what the current rating of each winding is. The power consumption is stated to be 120 watts so at the 120 VAC input shown, that would be around 1 A and the input fuse is 2 A. If the fuses in the secondaries are also about the 2:1 ratio then you can guess that the current for the secondaries is half the fuse rating for that winding. You can double check by adding the measured secondary voltages times their current guess and see if the total is close to the 120 watt total consumption.Most equipment doesn't have all the secondaries fused like this unit and without that information you wouldn't know any of the currents on the multiple windings. This would be the same as if you used a meter figured out the primary winding and test powered it through a lamp to make sure then measured the secondary voltages. You know the voltage on each winding but you have no idea the current rating of each winding.If you take the end shells off the transformer and can see where the solid wire comes from the bobbin you can make an estimate by looking at the relative wire sizes. If I recall years ago when I wound some transformers there was some constant, perhaps between 750 and 1000 that you divided the circular mils of the wire by to get an estimate of current.Fun exercise to try to figure it out and I've saved a lot of similar transformers but it is much better if the transformer you find has the rating printed on the transformer!

author: Cubdriver
author_rank: Unknown
timestamp: May 04, 2019, 04:54:44 am
content: Quote from: MarkF on May 03, 2019, 11:32:42 pmGiven that electrotanya schematic, my guess would be that the brown wire might be the 120V primary tap - check to see if it has continuity with the black, violet and grey wires. If that is correct, the resistance between the black and grey will be highest, black and violet less, and black and brow the least of the three.-Pat

author: MarkF
author_rank: Super Contributor
timestamp: May 04, 2019, 08:16:43 pm
content: Quote from: Cubdriver on May 04, 2019, 04:54:44 amYes. I totally misread the voltages on this last diagram.I believe this is what the transformer looks like.However, the first diagram shows the red winding as 1A and the second diagram show it as 630mA.Checking the resistance between the four primary wires should verify this.

author: Jwillis
author_rank: Super Contributor
timestamp: May 04, 2019, 09:29:28 pm
content: That model RT-701 had several versions.RT-701/KU = #3603301~ (Canada/USA) 120VRT-701/KC = #3400001~ (Canada/USA) 120VRT-707/KU = #3606301~ (Canada/USA) 120VRT-707/KC = #3400001~ (Canada/USA) 120VRT-707/D = #9301201~ (US Military) VariousRT-707/DG = #9301001~ (General Export) variousRT-707/HG = #8400001~ (Europe/Oceania, Scandinavia, UK) 220 - 240 VThis would explain the different primary configurations of the transformer.The second number would be the beginning of the serial number probably on the back somewhere.

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 04, 2019, 10:32:32 pm
content: The Brown wire does in fact have continuity with violet black and gray

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 04, 2019, 10:38:16 pm
content: Brown to gray 6.8 ohmsBack to gray 10.3 0hmsBlack to violet 10.3 ohmsbrown to violet 5.7 ohmsbrown to black 3.7 ohms

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 04, 2019, 10:40:10 pm
content: I would have thought such a huge transformer would have been more amps ?? But the voltages are very high

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 04, 2019, 10:49:51 pm
content: MarkF you have voltage for the 2 green wires on the secondary side but on the transformer they are on the primary side. They do not have any continuity to the other primary wires.

author: Jwillis
author_rank: Super Contributor
timestamp: May 04, 2019, 10:52:41 pm
content: The size requirement of the core is dependent on the total current draw on all secondaries .so if you take the example by cubdriver .you add the current of all secondaries which is 6.5 amps so hence the large core area.Of course that's very simplified because each secondary carries a different voltageAs stated before secondaries can appear on the primary side simply for convenience of winding the bobbin .

author: queennikki1972
author_rank: Regular Contributor
timestamp: May 04, 2019, 11:19:36 pm
content: Im sorry I missed what you said about the green secondary wires on primary side in your earlier post.

author: MarkF
author_rank: Super Contributor
timestamp: May 05, 2019, 02:13:03 am
content: Quote from: queennikki1972 on May 04, 2019, 10:49:51 pmThe physical side the wires come out of the transformer is irrelevant to whether it is a primary or secondary winding.Look at a toroidal transformer for instance. Most of the time all the wires come out at the same place.Quote from: queennikki1972 on May 04, 2019, 10:38:16 pmBLK-BRN(3.7) + BRN-VLT(5.7) = 9.4 ? BLK-VLT = 10.3According to your numbers, I think the transformer windings are like this.It seems a little funny where the 120V tap is. Maybe that makes a wiring connection that is simpler.

author: Cubdriver
author_rank: Unknown
timestamp: May 05, 2019, 02:17:13 am
content: Another thing to keep in mind about transformers is that they transform voltages and currents, but power (voltage multiplied by current) stays the same (less some relatively small losses; nothing is perfect).As a simple example, if you have a step up transformer that has a 10:1 secondary to primary ratio, it will put out 10x the input voltage. Put 120 in, you'll get 1200 out. You'll also get 1/10 of the current that flows in the primary - if you pull 100mA (0.1A) from the secondary, there will be 1A flowing in the primary (ignoring losses). This would be considered to be a 120W transformer. Conversely, if the ratio is opposite with 1 turn on the secondary for every ten on the primary, the output voltage would be 1/10 that of the input (12V), but for that same 1A primary current, you would draw 10 amps. It would still be considered a 120W transformer, and would be about the same size as the previously mentioned step-up unit mentioned earlier.Other than for transformers at the extremes (insanely high voltage or insanely low current, either of which might require specialized construction due to the need for insulation in the HV case, or very heavy wire in the LV, high current case), you'll find that transformers of a given power handling capacity are generally about the same physical size. Power capacity can be determined (if the secondary voltages and currents are listed) as someone mentioned above by multiplying each voltage by the associated current to get the power, then adding the power values to get the total. In short, just looking at a transformer usually won't tell you much about its input or output voltages, but will give you a feel for how much power it can pass.I hope this makes sense rather than muddying the waters for you.-Pat

author: MarkF
author_rank: Super Contributor
timestamp: May 05, 2019, 05:34:51 am
content: Quote from: queennikki1972 on May 04, 2019, 11:19:36 pmI don't know what you are referring to?

author: soldar
author_rank: Super Contributor
timestamp: May 05, 2019, 08:00:10 am
content: Quote from: MarkF on May 05, 2019, 02:13:03 amWhat if you look at it like this:There is a good chance the two 120 V sections are of different wire thickness and resistance and the lower resistance winding should be used. BLK seems to be the common for all voltages and BRN for 120 V. Resistance measurements confirm this.

author: MarkF
author_rank: Super Contributor
timestamp: May 05, 2019, 10:29:09 am
content: Quote from: soldar on May 05, 2019, 08:00:10 amIf the BLK to BRN winding has a heavier gauge wire, why are they using the BRN to GRY winding for the 120V input which would require more current?In the circuit diagrams, the 120V input has a 2A fuse while the 240V and 220V inputs have a 1A fuse.

author: soldar
author_rank: Super Contributor
timestamp: May 05, 2019, 10:44:00 am
content: Quote from: MarkF on May 05, 2019, 10:29:09 amWhere can I see the schematic?

author: MarkF
author_rank: Super Contributor
timestamp: May 05, 2019, 11:16:29 am
content: There are two links above (copied here):https://www.esotericsound.com/SalesImages/rt-707sm.pdfandhttps://elektrotanya.com/pioneer_rt-701_rt-707_art2540_additional.pdf/download.html#dlYou can also look at screen captures I posted earlier in this thread if you don't want to search the documents (Reply #19 and #20).Edit: The 120V transformer in the circuit diagram is a RTT-116. I can't find the part no. for the 240V/220V transformer.The transformer she has is a RTT-118.

author: MarkF
author_rank: Super Contributor
timestamp: May 05, 2019, 12:42:01 pm
content: I found a RTT-116 transformer on eBay. It only has one primary winding.So, we can not use it as a wire color reference.I am beginning to think @soldar is right...BLK and BRN for 120VBLK and VLT for 220VBLK and GRY for 240V

author: 6PTsocket
author_rank: Regular Contributor
timestamp: May 07, 2019, 12:57:58 am
content: Quote from: MarkF on May 03, 2019, 10:48:16 pmThe AC line in Japan is 100 volts so one extra primary tap might be for that. I recall Japanese hi fi equipment that had a 100 volt tap for domestic consumptionSent from my SM-G900V using Tapatalk

author: MarkF
author_rank: Super Contributor
timestamp: May 07, 2019, 01:39:38 am
content: Thanks.I thought there was another standard voltage that I've seen as selectable on some equipment.(i.e. 100VAC / 120VAC / 220VAC / 240VAC)

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 07, 2019, 02:31:07 am
content: You are correct.100 VAC is the household voltage in Japan.

author: MarkF
author_rank: Super Contributor
timestamp: May 08, 2019, 09:29:37 am
content: A little bored. So, I thought I would summarize our findings.It hasn't been obvious but the BLU to YEL winding could be used for another 30VAC.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2019, 06:59:53 pm
content: And Violet to Brown for 100V mains input? (Japan)Assuming the wire gauge supports the current required.