[x300] X300 - XJ6 - Illumination Module - AGAIN!

X300
1

I am not having any luck with the Illumination Module

I replaced it last September after it melted and nearly
caused a fire

I repaired a poor crimp connction in the new module in
February this year.

Now, again, this evening it has overheated and melted and
nearly caused a fire (though I was ready for it and did a
very quick battery disconnect - thankfully I have fitted a
battery switch !)

So what gives - I don’t think the car wiring is at fault as
I tested it thoroughly last time. Could be a bit of chafing
somewhere - but then why didn’t it blow the fuse ?

Took the unit apart and the power transistor is marked

PSSNF06
CCO7J
MAR 515

see picture on my page http://tinyurl.com/389hodk

Anyone recognise this number or tell me a good substitute ?

Long shot I know, but there are many electronic guru’s out
there (I hope)

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

Teamwork is a lot of people doing what I say–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

2

In reply to a message from sfj642 sent Fri 25 Mar 2011:

Jim, a quick search hasn’t thrown up anything on the
transistor, but haven’t you substituted LEDs and various
bulbs, are these causing too higher drain and cooking that
chip i.e. is that acting as a fuse? Just thinking aloud.–
The original message included these comments:

I tested it thoroughly last time. Could be a bit of chafing
somewhere - but then why didn’t it blow the fuse ?

–
Neil '97 3.2Sport http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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3

In reply to a message from Neil Maldon sent Fri 25 Mar 2011:

Neil

Have fitted about four LED’s only - they take far less
current than an incandescent bulb so should have rduced, not
increased the load.

Chances are that the unit is an aftermarket unit made in
China - although it has a Jaguar LXF 6490 AA plain label on
it (no Jaguar picture). Also - had I overloaded it that
much, why didn’t the fuse blow first?

I might get away with just a new power transistor if I can
find the right spec.

Have you noticed (like toothache) these things always happen
on a Friday evening when no-one is open until Monday!

Back to the Austin - that just has an on/off switch for the
dial lights ! :-))

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

Why doesn’t glue stick to the inside of the bottle?–
The original message included these comments:

transistor, but haven’t you substituted LEDs and various
bulbs, are these causing too higher drain and cooking that

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
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4

In reply to a message from sfj642 sent Fri 25 Mar 2011:

Jim - I’m very sorry to hear you’re in trouble with this
module again.

Firstly, the device you mention is a fairly common power
MOSFET, good for 50A and 60V. The particular one you mention
is made by SGS-Thomson. I use a Fairchild equivalent in a
few of my controller designs so I have them in stock. If
you’d like to forward your address to me via e-mail, I’ll
gladly put a few in a jiffy bag for you to have a go with.

Secondly - about the recurring problem: When you first
mentioned this module some months ago, it prompted me to go
and find a cheap one on Ebay for research purposes. I found
a working one for �7 which fitted the bill. I’ve analysed
the circuit and I think it’s sorely lacking.

To cut a long story short, there’s a PWM chip which drives
the power MOSFET. In my module, the MOSFET is a BUZ11, which
was an early type and not so robust as later ones. The PWM
chip has facilities for detecting overcurrent and switching
the MOSFET off in that event to protect it. Problem 1: This
feature is NOT implemented in the design. Problem 2: the
MOSFET is the ONLY switching element between the
permanently-live +12V feed and the lighting circuit.
Therefore, if it begins to leak, there is nothing else in
series to disconnect the current. Problem 3: although
MOSFETs make excellent switching devices, they need some
extra protection around them to guard against odd brief
voltage spikes, which will cause (partial or full) failure.
There was practically no protection in the module I analysed.

As you probably already know, MOSFETs have various failure
modes. One such is where they start to leak (i.e., pass some
current when they’re supposed to be ‘off’). Suppose the
MOSFET leaks something like 0.3A at 12V when you believe the
lighting is switched off. That’s not enough to light all
20-odd bulbs on the illumination circuit as they’ll form a
very low resistance, being mostly cold. The leaky MOSFET
appears as a resistor in series with the lamps and most of
the 12V will be dropped across the supposedly ‘off’ MOSFET.
Result: heat!!! And no way of disconnecting the flow,
either. The current is not enough to blow the fuse, so that
stays intact. But it is enough to start a cooking process in
the module. And, even if it doesn’t immediately cook, the
battery will run down, seemingly inexplicably, faster than
it should when the car is unused for a few days.

One item on my ever-growing ‘To-do’ list is to finish a
re-design of this module so that there’s another switching
element in series with the MOSFET, and also proper current
limiting and protection. But you know how it is: ‘real’ work
keeps on getting in the way…

Hope this sheds some light, anyway! (And sorry about the pun.)

Cheers,
Gerald.–
The original message included these comments:

I am not having any luck with the Illumination Module
I replaced it last September after it melted and nearly
caused a fire
So what gives - I don’t think the car wiring is at fault as
I tested it thoroughly last time. Could be a bit of chafing
somewhere - but then why didn’t it blow the fuse ?
Took the unit apart and the power transistor is marked
PSSNF06

–
1996 X300 4.0
Suffolk, England, United Kingdom
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5

In reply to a message from edenyard sent Sat 26 Mar 2011:

Gerald

SHEDS of light, and many thanks for your technical appraisal.

Although I drifted into the transistor and IC era, most of
my time was spent with valves (including the vintage 1920’s
BBC medium wave transmitters). At least you could trace a
signal through them - one valve, one process !

Without a diagram, I couldn’t work out the circuitry of the
illumination Module - though it was fairly obvious what had
failed ! Trouble is that it could take the wiring with it
if I wasn’t technically aware and acted quickly to
disconnect the battery. Your summary of the un-connected
fail-safe mechanisms and the creeping failure mode fills me
with concern :-((

At least I can begin to think it is not an obscure fault
with the car wiring - logic would suggest that a short
should blow the fuse first ! There was a Jaguar technical
note re the possibility of chafing the wiring loom behind
the radio - I had a good look last time and shall do so
again before powering up !

Again - many thanks for a super post

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

A job is easier to do if you know it can be done–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
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6

In reply to a message from sfj642 sent Sat 26 Mar 2011:

Gerald

As this post has been mentioned in despatches . . .

Thanks so much for all your help; the Jaguar is back on the
road with a working illumination control module. I have
added close-rated quick blow fuses in the input and both
output leads - hopefully these will blow in preference to
having another potential bonfire !

Rather worrying that the 10amp fuse in the LH heelboard is
rated to supply both the heated mirrors AND the illumination
module. This means that well over 10 amps can flow into a
faulty Illumination Control module without the fuse blowing

  • worrying and not good design.

I hope to find out the REAL blowing current of the fuse soon.

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

The above opinions are not necessarily my own; my dog has
learned to type–
The original message included these comments:

SHEDS of light, and many thanks for your technical appraisal.

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
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7

In reply to a message from sfj642 sent Tue 5 Apr 2011:

Have just tested the blowing current of 10 amp fuses that
supply the Illumination Control module.

The plot thickens and has a rather worrying conclusion:

Out of interest (together with an element of suspicion), I
tried to blow two of the 10amp fuses that would have
supplied the Illumination Control module. They each took
23amps continuous current - got hot (melted the plastic) but
didn’t blow. Same with a 7.5amp fuse - took 23amps without
blowing.

This means that, should a module go faulty (as opposed to a
dead short) then up to 25amps could pass continuously into
the fault.

At 12volts that is 300watts and is most likely the reason
the wiring on my car got so hot when the Illumination
Control Modules failed :-((

I always suspected that car fuses would take more than
specified - this more than proves the point. My bench
supply wouldn’t provide more than 23amps so the actual
fusing current could have been even greater.

So - fault on Illumnation Module - increase in current -
smoke etc and the fuse still won’t blow. Definitely
dangerous.

I have added close-rated quick blow fuses in the input and
both output leads - hopefully these will blow in preference
to having another potential bonfire !

see my page http://tinyurl.com/389hodk for a picture
(bottom of page).

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

If it isn’t broken, fix it untll it is —
this time it WAS broken and I think I fixed it.–
The original message included these comments:

I hope to find out the REAL blowing current of the fuse soon.

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
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8

In reply to a message from sfj642 sent Wed 6 Apr 2011:

Slightly worrying Jim, I’ve always taken things like fuses
at face value and as yet have had no problems… BUT! With
regards checking a 10A out to destruction, why not rig a
battery with a rheostat or resistor stack and see exactly
what it takes to cook one?–
The original message included these comments:

supplied the Illumination Control module. They each took
23amps continuous current - got hot (melted the plastic) but
didn’t blow. Same with a 7.5amp fuse - took 23amps without
specified - this more than proves the point. My bench
supply wouldn’t provide more than 23amps so the actual
fusing current could have been even greater.

–
Neil '97 3.2Sport http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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9

In reply to a message from Neil Maldon sent Thu 7 Apr 2011:

Neil

I just bought a 1ohm 250watt variable to do the load tests -
and naturally thought 23amps would be more than enough to
blow a 10amp fuse.

Now the problem is I don’t have a reasonably accurate 30amp
meter except on the bench supply. The old Lucas car ammeters
would only give an approximate answer.

Remember I have been looking for the reason my wiring cooked
up when the Illumination Control Module went bad. The
REASON the module went bad is still not certain.

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

Teamwork is a lot of people doing what I say–
The original message included these comments:

regards checking a 10A out to destruction, why not rig a
battery with a rheostat or resistor stack and see exactly
what it takes to cook one?

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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10

In reply to a message from sfj642 sent Thu 7 Apr 2011:

Jim I think Gerald came close to that with his analysis of
the design, the drive TR is not well protected and a soggy
fuse probably compounds that. If you Butter(worth) him up he
may just come up with a mod!–
The original message included these comments:

Remember I have been looking for the reason my wiring cooked
up when the Illumination Control Module went bad. The
REASON the module went bad is still not certain.

–
Neil '97 3.2Sport http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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11

In reply to a message from Neil Maldon sent Thu 7 Apr 2011:

Neil

Gerald and I have been chatting off forum and yes, has
suggested some mods.; one of which is under test at the moment.

But the background to all this seems to be that my car is
the only car that has had this problem of cooking up. It is
acknowledged the Illumination Control modules fail - but so
far I’ve not seen any cases of the same failure mode which
might lead to potential conflagration.

Let us hope it doesn’t happen to anyone else and my car has
a unique problem. :-((

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

Frustration is trying to find your glasses without your glasses–
The original message included these comments:

Jim I think Gerald came close to that with his analysis of
the design, the drive TR is not well protected and a soggy
fuse probably compounds that. If you Butter(worth) him up he
may just come up with a mod!

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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12

In reply to a message from sfj642 sent Thu 7 Apr 2011:

Jim Ohm’s law and physics dictate that you need a
source(battery 180 AH ~ 2KW) and a sink (dead TR ~ Ground)
Fuse (10 ?A) Loom wire (? Ohm) carrying 180A (ish) lots of
watts!
Remember the DC valve heater circuits on the big broadcast
Tx’s don’t know if you ever saw the result of a S/C near the
end of the loom or the smoke produced in a couple of
seconds, all that with 6v and about 50A!

I’d still worry why the fuse isn’t blowing.–
The original message included these comments:

But the background to all this seems to be that my car is
the only car that has had this problem of cooking up. It is
acknowledged the Illumination Control modules fail - but so
far I’ve not seen any cases of the same failure mode which
might lead to potential conflagration.
Let us hope it doesn’t happen to anyone else and my car has
a unique problem. :-((

–
Neil '97 3.2Sport http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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13

In reply to a message from Neil Maldon sent Thu 7 Apr 2011:

Neil - you may enjoy this; not a lot - but it should be a
warning to all.

If a blade fuse looks like a blade fuse and has a 10amp
rating marked on, you assume it to be a 10amp blade fuse. WRONG

I have just gone through a number of my spare fuses and
discovered that none of them would actually blow, but
preferred to melt at 300% overcurrent.

I checked the few original remaining fuses in the spare
fuseholder in the car toolbox - they all blew at rating plus
about 20%, no more. Perfection.

SO there are good fuses and bad fuses. The eBay listings
only seeem to offer unbranded types - having been caught out
once I won’t be going down that route again.

The original fuses were made by Littelfuse - and so after
some hunting I have ordered a set A04030 to be sure of
having fuses that will actually BLOW when overloaded.

I checked the other fuses in the left-hand heelboard fusebox
and they were all original made by Littelfuse - I shall be
checking the others tomorrow !

DO NOT BUY UNBRANDED FUSES (even if they are the only ones
you can find).

Best wishes from Jim Butterworth
http://www.watchet.dolphins.btinternet.co.uk/

Just because you’re not paranoid doesn’t mean they’re not
out to get you–
The original message included these comments:

But the background to all this seems to be that my car is
the only car that has had this problem of cooking up. It is
acknowledged the Illumination Control modules fail - but so
far I’ve not seen any cases of the same failure mode which
might lead to potential conflagration.
Let us hope it doesn’t happen to anyone else and my car has
a unique problem. :-((

–
Jim Butterworth http://www.jag-lovers.org/v.htm?1262090878
Somerset, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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14

In reply to a message from sfj642 sent Thu 7 Apr 2011:

Thank god for that Jim, it had to have a reason if there are
duff fuses out there we need to beware. I’ve always bought
mine from reputable outlets and my current Jag was dealer
serviced prior to my buying it, but I’ll still have a check.

Glad you’ve discovered why it was happening, I think I’ve
said this before: ‘‘Never assume CHECK!’’.–
The original message included these comments:

Neil - you may enjoy this; not a lot - but it should be a
warning to all.
SO there are good fuses and bad fuses. The eBay listings
only seeem to offer unbranded types - having been caught out
once I won’t be going down that route again.
DO NOT BUY UNBRANDED FUSES (even if they are the only ones
you can find).

–
Neil '97 3.2Sport http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –