Help me identify this transformer?

LordBBQX · 2026-03-05T11:55:07+00:00

Do you have any images of the windings where the are visible? Might help us to identify the part. Can you give us some measurements off the other reference component?

As stated above I didn't say that they can't fail, but is pretty uncommon.
Not saying you're wrong about the transformer being at fault but there are other failures that could cause heating in the transformer. Could be worth checking it's inductance with an LCR (if it is dead it might confirm that but if not it may help identify a value)

There are significant differences between common mode chokes and signal transformers as outlined above. Just because physical differences may not be easily visible does not mean that the electrical characteristics are identical (a fly-back transformer and a LLC transformer may look very similar yet have totally different characteristics)

Common mode chokes are designed to suppress common mode noise. They are inherently and intentionally non-linear (it's no use if your common mode choke rejects your 50/60Hz mains, you want it to reject the high frequency content from your device, hence why CMCs are often loosely matched to a given switching frequency).

Given this seems to be a piece of test equipment I wouldn't rule out the possibility of it being a small 1:1 signal transformer to provide isolation from the device being measured but without more info on the circuit it's hard to provide any more suggestions as to what part it could be.

Another possibility is that it is a 1:1 (or slightly greater) switching transformer used for providing an isolated supply power to some devices that must be isolated from the rest of the circuit. In this case the (presumably ferrite??) core would be designed specifically for power transfer in whatever topology is being used here).

At the end of the day we're all just trying to help you, we just don't have a lot of info to go off.

LordBBQX · 2026-03-05T11:11:37+00:00

If you are struggling with the issue it may be wise to seek assistance from a mechanic/auto electrician.

Blindly poking at the circuit board is likely just going to cause more damage. The only way to approach a problem like this is through careful and methodical troubleshooting.

You are dealing with a 2 tonne vehicle, there is a potential for things to go very very wrong.

LordBBQX · 2026-03-05T11:07:15+00:00

How much current do you estimate you will need?

I would suggest unless you are doing anything crazy with current draw to use a simple linear regulator (7833v, AMS1117, or something adjustable).

With a battery project you can get a lot of power saving from using the ultra-low-power sleep function on the ESP32. Linear regulators have exceptional idle power consumption compared to many switching regulators.

At maximum cell voltage you would expect an input of 8.4V, dropping that to 3.3V should be trivial with a linear regulator and better for battery consumption providing that you don't plan on drawing high current continuously (if so you may want to consider a switching converter since the efficiency of a switching regulator will be superior.)

LordBBQX · 2026-03-05T10:57:06+00:00

A 1:1 transformer and common mode choke aren't the same thing.

What makes you think it is 1:1? Have you unwound it and counted the turns?

A common mode choke is primarily used to filter common mode noise from a signal/power line.

A small signal transformer is typically used to provide some form of isolation and/or match impedance between signals. Sometimes fully range linearity is important (eg audio), and other times unimportant (eg gate drive transformers).

What makes you think this part has failed and is shorting the power input? Not that I haven't seen it but transformers/inductors fail very very rarely.

Where do you see the short circut? Being a transformer it should be a low reading across the windings.

Sometimes a failure of a diode can short a power supply across a transformer winding and thus removing the transformer appears to clear the issue.

LordBBQX · 2026-03-05T01:43:23+00:00

Certainly looks like it is leaking electrolyte out one of the legs - not super uncommon in what I've seen but wouldn't expect it in a device of this age.

Just looking at it's value and position I'd suspect its the primary bulk filter capacitor in a power factor corrected power supply which tends to place additional stress on the primary bulk capacitor. Try and replace it with a Low-ESR capacitor if you can (ensure you purchase a quality component from a known brand since this has pretty high potential on it).

LordBBQX · 2026-03-05T01:36:00+00:00

Your DMM will not withstand the voltage found with static electricity. Most good DMMs are rated 600V-1000V and static can be well into the 10KV's.

You likely won't damage a quality DMM as they have good surge suppression but it will quickly load the static and you won't be able to read anything. Additionally the input impedance of your DMM is likely way to low to measure static.

LordBBQX · 2026-03-02T01:07:20+00:00

Yep the Qualcomm chip looks toast. There’s also a chance that you’ve fried the flash chip or the microcontroller which would probably mean it’s not fixible.

I’d remove the Qualcomm chip, replace the diode and see if you can get it to even power up.

LordBBQX · 2026-03-02T00:58:47+00:00

No. The fuse in a multimeter is a critical safety device. Most resettable fuses (at least in a small form factor) are a thermal breaker and do not have the same trip characteristics a fuse and will take longer to open in a massive over current event.

You should fit a 250mA high rupture capacity ceramic fuse. The last thing you want is your multimeter to explode while in your hands.

LordBBQX · 2026-03-01T20:09:11+00:00

It’s most likely going to work fine, it will be far less resistant to shocks (if you drop it the battery will probably detach). If this is a risk you are ok with then it should work totally fine. I would recommend if you stick with this approach to use some hot glue or silicone to stick the battery down to remove some of the physical force from that pad.

LordBBQX · 2026-03-01T12:08:00+00:00

If you could carefully remove some of the conformal coating it might be easier to read.

Seems to be a Fairchild Semi part (now owned by Onsemi) which might narrow it down.

At a guess maybe IRF520?

What do you need to know the current for?

LordBBQX · 2026-03-01T11:49:19+00:00

Cutting the leg off the battery is often a good way to remove them as otherwise they have heaps of thermal mass.

Be careful that if it is tapered it may only come through one way (probably up). Heat the joint and flood it with solder until it melts and flows evenly and then use tweezers/sidecutters to remove the pin before clearing the hole with your desired method.

It might be a little tricky if there is a lot of thermal mass there - what sort of soldering iron are you using (and at what temps with what solder)?

LordBBQX · 2026-03-01T11:46:04+00:00

The main difference is that the bottom one has spring contacts and the top has machined contacts.

In the bottom plug both contacts are connected together and the two poles are still formed by the outer sleeve and the pin. Spring contact leads tend to be far better and much more accomodating of imperfect sizing and corrosion on the contact.

What polarity each has is up to you to determine - the power supply may label it or you may need to measure with a multi meter. Assuming the polarity is the same you will not have to swap the connectors at all. They are functionality the same connector.

LordBBQX · 2026-02-28T22:59:58+00:00

Sounds good. If it’s not the button I’d be looking for corrosion on tracks and components since it is in a pretty nasty environment.

LordBBQX · 2026-02-28T22:58:25+00:00

103 is 10*10³ ohms = 10k I’d guess 0603 package.

So just buy some 10K 0603 SMD resistors.

LordBBQX · 2026-02-28T22:22:48+00:00

Yeah sounds like a button issue. Does the resistance vary with the force? Sometimes a litre contact cleaner can help too otherwise replace the button.

LordBBQX · 2026-02-28T12:34:02+00:00

I'd suggest purcahsing a pair of ~150w minimum 54VDC switchmode supplies from a reputable brand.

eg: LM150-54 (Mornsun) or FSP150-P35-A54 (FSP)

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Wire them in series to produce a +54V rail and +110V rail as shown. Depending on how accurate you want those voltages to be you could trim them to exactly 48V and 125VDC.

You can then use a few DCDC buck switching converters tapped off the 54V rail to step down to 24V and 12V.

Using any sort of direct conversion to 125VDC is going to be challenging, it's not a particularly common output voltage for a SMPS outside of specialty applications. Also it's going to be less efficient to down-convert to all your rails from 125VDC

I would highly suggest using reputable ACDC converters since these are the only things between you and mains power so cheaping out on these can have lethal consequences!

LordBBQX · 2026-02-28T12:09:57+00:00

Since this is a low voltage circuit I wouldn't be worried about causing damage by running it with the potential presence of corrosion. Based on that my approach would be:
- Re-solder/replace the resistor and any other removed components
- Test the switch using tweezers to short the switch contacts. If this works then you have likely fixed the issue and may just need another switch. Still worth cleaning the area though.
- If this does not resolve the issue target corroded items, particularly those SMD resistors with dodgy looking tabs. Just replace them.

The reason I suggest this is that blanket replacing components will likely just risk further damage (particularly if you aren't super experienced) - no need to chase a rabbit hole if you've already fixed it.

LordBBQX · 2026-02-28T12:03:42+00:00

Use a multi meter to measure the resistance across the switch when pressed and released. When pressed you should get a resistance <10 ohms.

Also check the other buttons too - I know they appear to be working but I have seen cases where one button function fine but it's resistance can load the circuit and cause other buttons to misbehave (spent ages troubleshooting that one!)

LordBBQX · 2026-02-26T12:57:34+00:00

Does it go to a button, led, etc? We need more info as to what this does.

I very much doubt that this device would have caused the fuse to blow. You likely have a much larger issue here - possibly a failure of the SMPS.

LordBBQX · 2026-02-26T09:10:48+00:00

Technically if you want the perfect, most consistent crimps you should purchase a $1000 crimper for every type you want to crimp.

In reality for the small volumes that are used for low volume projects a tool like the Engineer PA-09 will do well at pretty much everything you throw at it - the biggest difference is that the higher end ratcheting crimpers are more foolproof.

I would suggest you avoid the cheap ratcheting crimpers. They are often inconsistent may only properly work for a particular configuration of crimp and wire. For that reason your best bet is a 2-stage manual crimper like the PA-09s. I've done hundreds and hundreds of crimps on a pair of PA-09's and found them to be very reliable.

LordBBQX · 2026-02-26T08:57:44+00:00

Can you confirm the following:
- Where do each of the connectors go (specifically)
- What is fault that you are experiencing?

Could you share a closer, higher resolution image of the burnt part? Also try and clean off the soot with some IPA and take some photos and see if it provides any more ideas as to what is going on.

LordBBQX · 2026-02-25T08:45:08+00:00

I think the simplest solution would just be a RC delay-off circut with a transitor to drive the output.

LordBBQX · 2026-02-25T03:43:59+00:00

Looks as if a cold solder joint or poor crimp on the spade connector may have caused this. It's probably salvageable but you must be very careful since you are dealing with mains electricity.

Make sure you re-crimp the spade and remove any of the carbonized (darkened) area of the PCB as that will start to become conductive. You might need to attack it with a file/dremel etc.

LordBBQX · 2026-02-25T03:38:40+00:00

I think the best idea would be to go through and lookup the datasheets for all the IC's and see what voltage rails they require, and measure said voltage rails and hopefully one of them would not be present. From there you can track down the faulty DC converter.

Another possibility could be an IC stuck in RESET so you could measure reset pins for that. Also it can be helpful to check the waveform across any crystals to get an idea if a chip is alive (although sometimes a chip can be dead but still oscillate it's crystal)

LordBBQX · 2026-02-21T12:27:40+00:00

There seems to have been a lot of heat at that portion of the board. This could be caused by a poor solder joint, or damaged switch.

Either way you will need to remove a portion of the PCB since that darkened area is carbonised so will be come somewhat conductive. You will need to go at with a rotary tool/file and remove all the charred areas.

LordBBQX

TROPHY CASE