Replacement Transformer - Page 1
Forum section: electronics / projects

author: Megawilsound
author_rank: Contributor
timestamp: November 01, 2020, 01:03:04 pm
content: Hi allI am looking for a replacement transformer the part number isNEL-D32-43. It is part of the EL back-light for a Roland D550 synth.I have not been able to find one online so I am looking for a modern one that I can replace the original with.I have attached the datasheet and photo of the original.ThanksMegawilsound

author: geggi1
author_rank: Frequent Contributor
timestamp: November 01, 2020, 03:20:46 pm
content: If the transformer is an 600 ohm transformer you should look for a telecom transformer.

author: Yansi
author_rank: Super Contributor
timestamp: November 01, 2020, 03:24:17 pm
content: EL backlight is a DC-AC converter to some hundred volts AC, definitely not an audio line thing!Whats wrong with the transformer you got?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 01, 2020, 06:24:10 pm
content: Replace the entire backlight with LEDs?

author: Megawilsound
author_rank: Contributor
timestamp: November 02, 2020, 10:10:47 am
content: HI allYansi, it is over 30 years old and has given up the ghost.NiHaoMike there is no way this can be done without modifying the unit. (LEDs)

author: Yansi
author_rank: Super Contributor
timestamp: November 02, 2020, 10:39:22 am
content: Quote from: Megawilsound on November 02, 2020, 10:10:47 amSo what is wrong with the transformer then? How did you conclude the transformer is at fault? I find it very unlikely for the transformer to fail.

author: Megawilsound
author_rank: Contributor
timestamp: November 02, 2020, 11:34:42 am
content: Hi YansiI have tested it with my multimeter on the input I get 1.7 ohms out gives O.L.that's what is telling me it needs replacement.Megawilsond

author: Yansi
author_rank: Super Contributor
timestamp: November 02, 2020, 12:23:26 pm
content: You even sure it is a transformer? Isn't it just plain inductor? Or an inductor with a tap (autotransformer)?Show us the schematic, or at least part of it nearby. Photograph the transformer in detail, near the pins.I still strongly doubt anything happened to it, let alone open circuit winding. Would look much different, when the winding would burn in half.

author: Megawilsound
author_rank: Contributor
timestamp: November 02, 2020, 12:54:21 pm
content: HI YansiIt is listed as an EL inverter in the service manual.with the part number NEL D32-43.The schematic is attachedThanksMegawilsound.

author: jiarui
author_rank: Contributor
timestamp: November 02, 2020, 02:12:08 pm
content: So, it's not quite a transformer. I have had a old Yamaha multi-track recorder where the back-light died. It turned out that the voltage regulator (In your case, the 7805) died. Have you checked the voltages at the 7805? The coil is part of a AC generator. The back light needs a couple hundred volts of AC power. You should check that part of the circuit with a scope to see what going on. It's also likely that the transistor could have died.

author: Megawilsound
author_rank: Contributor
timestamp: November 04, 2020, 03:06:53 pm
content: Hi AllSo no one knows of a possible replacement for the inductor.

author: sandalcandal
author_rank: Unknown
timestamp: November 05, 2020, 12:41:54 am
content: As per data sheet in the OP it's an autotransformer for a single transistor oscillator to drive an EL backlight. EL backlights are obsolete so you're unlikely to find any modern jellybean replacement transformers. Any equivalent replacements will also be quite difficult because the transformer will need to be matched to the oscillator circuit to function correctly. If you can't find NOS replacements then the best solution might be to replace the entire EL drive circuit. I haven't bought from these guys but a source of replacement complete EL backlight systems (panel+inverter) here:https://elpanelandtape.co.uk/el-backlights/You might be able to get away with just getting a replacement inverter but probably best to change the whole thing if you can and avoid any second guessing.As others have stated, I'd also question if its really the transformer that's broken. That range did you have it set to when you checked the out-gnd resistance? Since it's such a high ratio, low power transformer I wouldn't be surprised if the output winding was in the 100s of ohms.

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2020, 01:45:37 am
content: If it's an autotransformer it might be just fine, it's not unusual to have unused pins on small transformers like that.EL may not be used much as a backlight anymore but it is alive and well for artistic purposes. EL inverters are widely available on ebay and from the usual Chinese suppliers.

author: Yansi
author_rank: Super Contributor
timestamp: November 05, 2020, 12:03:07 pm
content: Quote from: Megawilsound on November 04, 2020, 03:06:53 pmNo because, it more than likely is a custom part made to fit the purpose.

author: sandalcandal
author_rank: Unknown
timestamp: November 05, 2020, 12:14:25 pm
content: Quote from: Yansi on November 05, 2020, 12:03:07 pmPossibly, but the attached datasheet makes it look like it was from a standard line of transformers sold for jellybean use in backlight EL inverters.

author: Yansi
author_rank: Super Contributor
timestamp: November 05, 2020, 12:45:25 pm
content: Okay, my fault, did not see the datasheet.But still doubt you could buy it anywhere. Even the have-it-all dark corners of china came empty.I have asked for a proof the transformer is wrong, but only got that "output is OL". What is output in your view?The transformer has 5 legs, out of which 4 are used. All pins 1-2-3-4 should have an electrical connection to each other. So which one does not have connection? Haven't you just torn it off when desoldering the transformer from the board?As I've said: I have strong doubts transformer can go open circuit by itself out of nothing. It was either damaged mechanically (wire broken by mechanical stress) or can go open circuit by a sustained overcurrent condition. In that case, other stuff would be burned too, such as the transistor. And the transformer would certainly hold the typical signs of burnout.Have you tested the transistor and the electrolytic capacitor in the base?

author: wraper
author_rank: Unknown
timestamp: November 05, 2020, 12:57:27 pm
content: Such transformers often have wire broken at the place where is wraps around the terminal. I would check that first, might be an easy fix.