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electrolux/vernitron 12v dc re-igniter

bazz

Jul 11, 2017
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Hi after getting wet this re-igniter stopped working closer inspection reveled a large plastic lump on one of the transistors(see wire pointing to it)would any one know what it is or a suitable replacement could be ? Thanks Bazz.
model no 407/1/72699/010
IMG_20170711_133844.jpg
 

Bluejets

Oct 5, 2014
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Large plastic lump is where it has blown it's top.
Can you read the numbers on the flat face of the device?
 

kellys_eye

Jun 25, 2010
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Is it blown? Or is it just a 'blob' of the coating that board looks to have been waved over?
 

bazz

Jul 11, 2017
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cant see any numbers on it,the plastic blob was a lot longer on it, i broke a bit off,all the other components look ok
 

kellys_eye

Jun 25, 2010
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You will have to pick the plastic off the case to reveal any markings. They're not easily seen in the first place and the plastic conformal coating hasn't helped.
 

bazz

Jul 11, 2017
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ok i will remove it first,would the other one possibly be of the same value ?
 

kellys_eye

Jun 25, 2010
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Possibly - but no guarantee.

Can we see a wider look at the whole thing and a view of the rear of the board?
 

bazz

Jul 11, 2017
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ok

IMG_20170711_133241(1).jpg IMG_20170711_184130.jpg

[MOD NOTE: PLEASE DONT post so many duplicates in future]
 

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bazz

Jul 11, 2017
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no numbers on the burnt trans,there are numbers on the other one but will have to remove to see them IMG_20170711_190054.jpg
 

kellys_eye

Jun 25, 2010
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Not a number or numbering scheme I've come across so it could be an in-house designation.

If you 'assume' both devices are identical then you'll need to remove the 'good' device to check the orientation of the leads (collector-base-emitter) as fitting a generic replacement is relatively easy provided you put the right leads in the right holes! But those transistor packages have many different lead configurations cbe, ecb, bce etc.
 

bazz

Jul 11, 2017
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ok,once removed how do i check the leads ? can i do this on my meter ?
 

kellys_eye

Jun 25, 2010
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The devices are different so checking the other won't help. The picture reveals the 'other' device to be a thyristor, not a transistor.

The bottom of the board is covered in [email protected] Clean it off and resolder the joints - there looks to be at least one 'dry joint' there that could be the cause of the fault.
 

debe

Oct 15, 2011
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Seen these type of igniters before on Gas apliances. They use a small DC-DC inverter to give a high voltage, this is stored in the dump capacitor, Then the stored voltage is dumped on the HV coil by the SCR which is probably trigerd by the neon bulb. Bit like CDI ignition system.IGNITER.jpg
 

bazz

Jul 11, 2017
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yes ,in my search for a schematic it keeps coming up with boiler parts,its from a gas fridge used in camper-vans so with a 12v dc input it keeps providing a spark until dc is turned off.
 

kellys_eye

Jun 25, 2010
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Such ignitors will usually only run whilst providing the ignition spark - once the pilot light is lit the power to them is usually removed.
 

73's de Edd

Aug 21, 2015
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Sir bazz . . . . .


I think that your problem possibly/ could have been related to the water, even though the unit is well waterproofed with an encapsulating covering. Looking as if possibly having used one TOUGH two part low viscosity encapsulant such as the Scotch #300 series.

HOWEVER . . .you do see the white powdery lime/calcium family deposits on the top and bottom in the YELLOW boxed area.

On the top terminals, you do see the verdegris deposits, which take a time to grow, this just was not overnite.

ALSO I think that you just had a big dried drop . . . a long time ago . . . of that encapsulate being the blob that you mention and see on the transistor. See a similar s p r e a d out drop on the ferrite dumbell inductor nearby.

After my reading the boards foil, I’ll just bet that is going to be an NPN transistor as that oscillator and probably using a 12 / 24V derived supply.

The most noticeable thing is that solder whisker / splash that seems to be right between the SCR’s Anode and gate. In the RED CIRCLE

Why don’t you do this?

Check out that pulled transistor and I am expecting it to be good and you finding ~600-800 mv Vf between its two Base to Emitter and Base to collector junctions, with its center terminal being its collector.

I can’t see other components on the back side with your pics coverage.

Clean the board of its top side and bottom side white deposits . . . the verdegris . . . can be done later on.

Reinstall the transistor


Use a DVM . . . due to its minimal circit loading . . . and put in ~ 500 VDC volts range and make connection to any point on the PCB foil pattern that covers most of the outer periphery of the whole board.

( See my negative terminal markup of the storage capacitor.)

If lucky . . . . . that caps max voltage spec might be marked somewhere upon its case.

The meter positive lead will TEMPORARILY go to the + terminal of that capacitor.

Scrape for connections to be made thru the encapsulant at your chosen test points.

Power up the unit and initially take a quick reading after ~ 5 seconds with your meters + probe then touched to the storage caps +, if the oscillator is working you should then see a DC voltage building up.

Take your probe away to preclude any loading, then wait another 10 seconds and see if the voltage is then greater.

If all is well, that voltage will store up and rise in level and trigger the spark / ignition coil.

Your pic did not permit viewing to see the additional components and their arrangements on the rear ledge.

I feel that the full storage capacitor voltage is going to the primary of the spark coil with its other terminal going to the anode of the SCR.

Its associated NE-2 lamp is its triggering device, and probably has a voltage divider pair of resistors associated with it so that there will be a higher voltage developed to dump into the spark coil primary.

If so, there may be upwards of 100-200 VDC on that storage capacitor being built up, while the voltage divider bridge is only feeding 1/3 of that voltage to the NE-2 trigger circuitry.

However it may be, when that NE-2 lamp detects in the 55-65 VDC across its terminals . . .being at its particular critical ionization and flashover threshold, the tube makes an orange blink and that voltage feed thru is connected to the gate of the SCR and it fully conducts anode to cathode.

( If the cap voltage is building up and you are in a subdued lighting, you could just slip a black tube over the NE-2 envelope sides and wait to see its flash from its top. )

That SCR connectivity dumps the full charge of the storage capacitor into the primary of the spark coil and a short duration high voltage spark level is created at that units secondary. (RED marked . . . . HV.)

If that solder whisker was present at your initial time of testing . . . that could have stopped all

Fill us in . . . . . .

BOARD MARKUP:

Igniter_schema.jpg


73’s de Edd
 
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bazz

Jul 11, 2017
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ok plenty to check,many thanks .the residue on the back is from hot glue that the board was embedded in,it cleaned up ok,the component tail between a-g lifted ok and wasnt making a connection,with a loupe i can see a dry joint as kellys-eye pointed out that is on the earth IMG_20170712_105532.jpg IMG_20170712_105612.jpg IMG_20170712_105523.jpg IMG_20170712_105508.jpg so will sort out .
 

Cannonball

May 6, 2017
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I like the way 73's de Edd explained how to test this problem. I learned something. Good job.
 
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