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Cheap automotive HID ballast teardown

djQUAN

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I have this defective ballast from dad's car. It came with his newly purchased used car and the HID drop in kit probably cost around US$40.

The lamp blinked and this ballast made an arcing sound so I replaced it and that fixed his lights. I decided to look inside out of curiosity and was surprised on what I found.

Yes, that is fine white sand in it which serves no other purpose I can think of other than as filler.
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And then there's the second layer of potting compound
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Desoldered the connector and ignitor block and the board came out
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I found the problem. This film cap had a crack and part of its guts blown out
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Board cleaned off of leftover potting compound and flux residue ready to be reassembled again
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Replacement cap from a CRT monitor. I'm well aware of the lower voltage rating but the input side comes from a 400V electrolytic. Besides, chinese spec is overrated. :D
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Reassembled everything and crossed my fingers. Flipped the switch expecting fireworks but it worked. :)
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Input power peaked at over 90W but later stabilized to about 42W once the bulb was at operating temp which is what a typical 35W ballast consumes.
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If interested, there are more pictures and circuit descriptions here: Cheapie Ballast
 

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Nice work. I can't tell you how many electronics I have fixed with a cap change out.
Flat screens, computer monitors ( crt and flat panels) stereo gear, powered sub
woofers, antique radios and on and on. Just fixed an antique Hammond organ for a friend about a month ago.
 

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If the device you're working on has the ability to output sound (a common one of course being a computer motherboard with a speaker connected) you can apparently tell if there are bad caps because of a screeching sound it makes. I've an old Mac that does this so badly I disconnected the speaker. It's indestructible though and still works 21 years on!

Nice work djQUAN, I'm not a fan of HIDs in cars as I think they're over the top (and I hate being on the receiving end of them), but I'm glad you fixed it. I actually think most forms of lighting these days are too much, we're in an age of dazzling cool whites and I hate it. A motorway can be lit just fine with well positioned 180W SOX but apparently anything less than clusters of 600W SON these days is unacceptable...!
 
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I had one fail and I tore it apart. I didn't take any pictures though. It was actually potted. This style:

Philips_ICs_and_NEC_Technical_Solution_HID_Ballast.jpg


The failure was in the starter. I'm not really sure how it happened, but the PCB material was a little charred and had become conductive enough that the starting pulse was just lost in the PCB. I "dremmel'd" away the darkened PCB and it started right up.
 

Fiddy

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great repair job! ive never opened up a HID ballast before, nice to know whats inside :)

I wonder if we could utilize the HV for tesla and HV experiments!
 

Benm

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Interesting teardown and solution of the problem. Makes you wonder how well up to spec the other components in the unit are, however.

The sand filler is also an interesting part. It could just be there as a filler to add some mass to the unit making it feel more 'sturdy', although it could also have some function in preventing arcing from the start pulse generator. Epoxy resin would have been a better choice, but if they'd had used that chances of indentifying and chiseling out this damaged capactor would have been slim :)
 

djQUAN

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Nice work. I can't tell you how many electronics I have fixed with a cap change out.
Flat screens, computer monitors ( crt and flat panels) stereo gear, powered sub
woofers, antique radios and on and on. Just fixed an antique Hammond organ for a friend about a month ago.

I swap out noname caps once I spot one. Sucks to have one blow up under normal use.

Nice work djQUAN, I'm not a fan of HIDs in cars as I think they're over the top (and I hate being on the receiving end of them), but I'm glad you fixed it.

HIDs are actually nice if used properly. I have a projector retrofit on mine. But with the proliferation of these cheap drop in kits and putting bulbs in the wrong optics plus improperly aimed is a recipe for glare and blinding light.

The failure was in the starter. I'm not really sure how it happened, but the PCB material was a little charred and had become conductive enough that the starting pulse was just lost in the PCB. I "dremmel'd" away the darkened PCB and it started right up.

The large block is the inverter which provides a 400Hz AC output. the smaller block is the igniter which is basically a HV multiplier which steps up the AC to 23kV to strike the lamp. HV and moisture is not a good mix which is probably the reason yours failed.

great repair job! ive never opened up a HID ballast before, nice to know whats inside :)

I wonder if we could utilize the HV for tesla and HV experiments!

Not sure if you could utilize it since it is constant power output and the HV is really only low current. The ballast usually shuts down if it detects that there is anything other than an HID bulb is connected at the output.

Interesting teardown and solution of the problem. Makes you wonder how well up to spec the other components in the unit are, however.

The sand filler is also an interesting part. It could just be there as a filler to add some mass to the unit making it feel more 'sturdy', although it could also have some function in preventing arcing from the start pulse generator. Epoxy resin would have been a better choice, but if they'd had used that chances of indentifying and chiseling out this damaged capactor would have been slim :)

weight difference without the sand is minimal. A fully potted (100% potting compound filled) ballast feels the same as the sand filled one. I'm guessing sand was used to lessen the amount of potting compound to fill the entire ballast up.
 
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I wonder if we could utilize the HV for tesla and HV experiments!

No. The starting pulse is up to a couple dozen kV, but the current behind it is minuscule. The actual operating voltage of the lamp is under 100V if I remember correctly.

[the sand] could also have some function in preventing arcing from the start pulse generator.

The pulse coil is already potted. That's the white box you see.
 

djQUAN

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I would also think that sand would be a poorer conductor of heat compared to potting compound so I still think sand was only used as a filler and nothing else.

edit: for those interested, you can read how these HID lamps work in this link:
http://donklipstein.com/d2.html
 
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Any of you gurus have tips on how to identify sense resistors? Like, I know a controller has to use resistors to sense how much current is flowing via how much voltage a known resistor drops, but what kind of controller would I be looking for? Is that what the op amp does, i.e. the little gnome with the valves? And if so, it would have to be a set of resistors that can trace back to pins on the op amp?

Nice work, DJQ, and thanks for sharing the pics and descriptions in your blog post!
 
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Like, I know a controller has to use resistors to sense how much current is flowing via how much voltage a known resistor drops...

Not necessarily. With AC it is more common to use a current transformer. They tend to look like a torroid choke, but with a wire running through the middle.
 

djQUAN

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This ballast actually has a sense resistor right before the H-bridge (which converts the DC-DC converter output to AC). It's a row of resistors on the bottom of the pic.
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There are many ways to sense current as cyp mentioned. It can be as simple as a sense resistor, a current transformer or even a hall sensing device. Most often, a resistor is used simply because it is cheap and simple to use for DC currents.

Often, a sense resistor is wired between the load negative and ground because it is easiest to measure the resulting voltage across it that way. Others use it on the high side (load +) so that the ground between input and output is uninterrupted.
 

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Thanks for the pointers! I've got a few used Philips 81522+ D2S bulbs that would make a nice spotlight, and aftermarket ballasts are getting cheaper and cheaper, hard for me to not turn this into another one of my incomplete projects :whistle:
 

djQUAN

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Here are some pics of another cheapie but seems to be better built. It was fully functional but the potting compound can easily be peeled off so I tore it apart to see what's inside.

These are the parts after peeling all of the potting compound off.
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These are the power devices. the four same parts are for the H bridge.
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Sub board which contains all the control electronics for the main DC-DC converter, the oscillator and drivers for the H bridge
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back side
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Main board which contains all power electronics
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Reassembled everything and it still worked :)
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Awesome repair job and pictures. I'm amazed you got the potting compound off, was it not the rigid stuff?

My eyes are overly sensitive to the far red spectrum, getting hit with standard incandescent headlights or even close proximity brake lights is painful. High color temp lights don't bother me nearly as much. And of course LPS is pain free. HPS don't bother me much unless it is excessively bright.
 

djQUAN

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The potting compound is the rubbery kind. I have several ballasts on hand and installed in our cars and when I come across spares that have the compound easily peeling off (and have a lot of free time) I try and tear it apart and peel everything off just to see how the ballast is built and see what parts are used. Other ballasts I have used similar rubbery potting compound but it sticks to everything inside so it's a pain to remove unlike these two.

I haven't noticed any sensitivity to a specific color of light but as long as it causes a lot of glare to me, I reach for my lightbar switch and fight back with 240W of LEDs on the roof or if the guy is from behind, I have a triple PT54 rear fog lamp. :evil:
 




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