Probabilities

Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.
I guess the question remains is, what did you use for replacement?

Jan Panteltje wrote:

Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.
I guess the question remains is, what did you use for replacement?

I can't see how they can go bad unless the leads eroded up inside the
encasement.

Jan Panteltje wrote:

On a sunny day (Sun, 07 Feb 2010 15:01:24 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
IHEbn.136047$kQ5.9674_at_newsfe08.iad>:


Jan Panteltje wrote:


Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

I guess the question remains is, what did you use for replacement?

I can't see how they can go bad unless the leads eroded up inside the
encasement.


Yes, possible, plastic transistors, but a short (varying say few hundred Ohm),
resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset circuit, the
other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

I have a bad batch of the MBT2222's at work that have little noise
spurs at a specific current curve, no matter what type of circuit you
put them in except for a digital switch. Acts almost like a
tunnel diode.
I keep them just to remind me how long it took to figure out why the
circuit I used them in acted like our GOV. erratic..

On a sunny day (Sun, 07 Feb 2010 15:01:24 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
IHEbn.136047$kQ5.9674_at_newsfe08.iad>:


Jan Panteltje wrote:


Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

I guess the question remains is, what did you use for replacement?

I can't see how they can go bad unless the leads eroded up inside the
encasement.


Yes, possible, plastic transistors, but a short (varying say few hundred Ohm),
resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset circuit, the
other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

I have a bad batch of the MBT2222's at work that have little noise

Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

On a sunny day (Sun, 07 Feb 2010 15:01:24 -0500) it happened
Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
IHEbn.136047$kQ5.9674_at_newsfe08.iad>:

Jan Panteltje wrote:

Just finished my PIC programer, used an 25 year old BC548 in
it.
Just after I posted that it worked OK, the LED started
flashing
on/off, and the PIC no longer communicated (it was still in
the
programmer).
Some measurement showed the BC548 shorting and putting 13 V
on the
PIC Vdd. The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped
working.
I thought, probability, same old batch, and indeed, after
some
testing also a BC548...

I personally think it has something to do with humidity,
perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those
in it.
I guess the question remains is, what did you use for
replacement?

I can't see how they can go bad unless the leads eroded up
inside
the encasement.

Yes, possible, plastic transistors, but a short (varying say
few
hundred Ohm), resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset
circuit,
the other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

On a sunny day (Sun, 07 Feb 2010 15:56:10 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
MvFbn.136050$kQ5.75667_at_newsfe08.iad>:


Jan Panteltje wrote:


On a sunny day (Sun, 07 Feb 2010 15:01:24 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
IHEbn.136047$kQ5.9674_at_newsfe08.iad>:



Jan Panteltje wrote:



Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

I guess the question remains is, what did you use for replacement?

I can't see how they can go bad unless the leads eroded up inside the
encasement.


Yes, possible, plastic transistors, but a short (varying say few hundred Ohm),
resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset circuit, the
other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?


I have a bad batch of the MBT2222's at work that have little noise
spurs at a specific current curve, no matter what type of circuit you
put them in except for a digital switch. Acts almost like a
tunnel diode.
I keep them just to remind me how long it took to figure out why the
circuit I used them in acted like our GOV. erratic..


LOL,
yes, and BTW I replaced one with one of the same old ones,
the other one I cut the wire to the collector, as it was hard to access, and already late..
ftp://panteltje.com/pub/board.gif
ftp://panteltje.com/pub/wire_cut.gif
Without the reset the thing works just as well...
Will replace it some other time...

Ha, I'm glad you can follow that pile of wires..

Yes, possible, plastic transistors, but a short (varying say
few
hundred Ohm), resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset
circuit,
the other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

I've used lots of BC548s and BC547s and never had a generic
complaint. Maybe you just have a bad batch or even a counterfeit
one.

Jan Panteltje wrote:

On a sunny day (Sun, 07 Feb 2010 15:56:10 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
MvFbn.136050$kQ5.75667_at_newsfe08.iad>:


Jan Panteltje wrote:


On a sunny day (Sun, 07 Feb 2010 15:01:24 -0500) it happened Jamie
jamie_ka1lpa_not_valid_after_ka1lpa__at_charter.net> wrote in
IHEbn.136047$kQ5.9674_at_newsfe08.iad>:



Jan Panteltje wrote:



Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

I guess the question remains is, what did you use for replacement?

I can't see how they can go bad unless the leads eroded up inside the
encasement.


Yes, possible, plastic transistors, but a short (varying say few hundred Ohm),
resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset circuit, the
other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?


I have a bad batch of the MBT2222's at work that have little noise
spurs at a specific current curve, no matter what type of circuit you
put them in except for a digital switch. Acts almost like a
tunnel diode.
I keep them just to remind me how long it took to figure out why the
circuit I used them in acted like our GOV. erratic..


LOL,
yes, and BTW I replaced one with one of the same old ones,
the other one I cut the wire to the collector, as it was hard to access, and already late..
ftp://panteltje.com/pub/board.gif
ftp://panteltje.com/pub/wire_cut.gif
Without the reset the thing works just as well...
Will replace it some other time...

Ha, I'm glad you can follow that pile of wires..

On Sun, 07 Feb 2010 19:10:34 GMT, Jan Panteltje
pNaonStpealmtje_at_yahoo.com> wrote:

Just finished my PIC programer, used an 25 year old BC548 in it.
Just after I posted that it worked OK, the LED started flashing on/off,
and the PIC no longer communicated (it was still in the programmer).
Some measurement showed the BC548 shorting and putting 13 V on the PIC Vdd.
The PIC lives, I replaced the transistor.
At almost the same time my old 8052AH computer stopped working.
I thought, probability, same old batch, and indeed, after some testing
also a BC548...

I personally think it has something to do with humidity, perhaps
combined with temperature changes?
That predicts trouble for all that other stuff that has those in it.

Are your transistors actually 25 years old? Please test if the
transistor case can be melted with a soldering iron. In 1993 a fire in
the Sumitomo Chemical factory caused a worldwide shortage of epoxy
encapsulation resin. Some of the replacement stuff proved to be of
inferior quality and enormously increased the failure rate of the
semiconductor devices.

Only a wild guess...

Piotr

Yes, possible, plastic transistors, but a short (varying say
few
hundred Ohm), resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset
circuit,
the other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

I've used lots of BC548s and BC547s and never had a generic
complaint. Maybe you just have a bad batch or even a counterfeit
one.

On a sunny day (Mon, 8 Feb 2010 03:04:29 +0530) it happened
"pimpom"
pimpom_at_invalid.invalid> wrote in
hknbl5$7j2$1_at_news.albasani.net>:

Yes, possible, plastic transistors, but a short (varying say
few
hundred Ohm), resistance between collector and emittor...
They hardly carry any current, 100k in series in one, reset
circuit,
the other one a few mA.
But they are nice and dry.. do not look eroded either.
Chip passivation?

I've used lots of BC548s and BC547s and never had a generic
complaint. Maybe you just have a bad batch or even a
counterfeit
one.

Yes so have I, but these are > 25 years old.

The proability of 2 failing within the hour after so long,
in totally different circuits, should be very small.

To the extend I considered an outside EMP source, but then why
only
these? And no nuke was triggered here that I know about