TECH: LOTR Ring Magnet Fuse/Q6- The Conclusion???

[Sonic]

Sonic here, posting for a friend that just bought his first pin - LOTR, and
sure enough F20 has blown

I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there was a
definitive solution. And it seems that Stern hasn't really issued a Service
Bulletin regarding this (well other than in 2004 - which is really lame) or
has Stern fixed it themselves (surprise, surprise).

At Q6, it appears that when Stern went from a 20A transistor to a 22A, the
problems became less frequent, but did not go away. So am I correct in that
the fix is to replace Q6 with an IRL540 (the higher current MOSFET). Does
that truly fix the problem ,or is that solution coupled with a change in
fuse value?

matt

[Lloyd Olson]

Ed at Great Plains sells a better transistor for that. It's been posted
before. I stuck one in my LOTR way back and no problems since. LTG :)

Post by Sonic
Sonic here, posting for a friend that just bought his first pin - LOTR, and
sure enough F20 has blown
I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there was a
definitive solution. And it seems that Stern hasn't really issued a Service
Bulletin regarding this (well other than in 2004 - which is really lame) or
has Stern fixed it themselves (surprise, surprise).
At Q6, it appears that when Stern went from a 20A transistor to a 22A, the
problems became less frequent, but did not go away. So am I correct in that
the fix is to replace Q6 with an IRL540 (the higher current MOSFET). Does
that truly fix the problem ,or is that solution coupled with a change in
fuse value?
matt

[Lloyd Olson]

Ed even posted it. LTG :)

Use IRL540's -- these are rated at 26 amps.
The 20N10L's were rated 20 amps. 20N10L's were obsoleted and replaced with
22NE10L's. The 22NE10L's are rated 22 amps.


You can find them here:
http://www.greatplainselectronics.com/products.asp?cat=17

Post by Lloyd Olson
Ed at Great Plains sells a better transistor for that. It's been posted
before. I stuck one in my LOTR way back and no problems since. LTG :)

Post by Sonic
Sonic here, posting for a friend that just bought his first pin - LOTR,

and

Post by Sonic
sure enough F20 has blown
I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there

was

Post by Lloyd Olson
a

Post by Sonic
definitive solution. And it seems that Stern hasn't really issued a

Service

Post by Sonic
Bulletin regarding this (well other than in 2004 - which is really lame)

or

Post by Sonic
has Stern fixed it themselves (surprise, surprise).
At Q6, it appears that when Stern went from a 20A transistor to a 22A, the
problems became less frequent, but did not go away. So am I correct in

that

Post by Sonic
the fix is to replace Q6 with an IRL540 (the higher current MOSFET).

Does

Post by Lloyd Olson

Post by Sonic
that truly fix the problem ,or is that solution coupled with a change in
fuse value?
matt

[GPE]

Dang it Lloyd! You beat me by 1 minute!!!
I guess you have speedier fingers than me!

-- Ed

Post by Lloyd Olson
Ed even posted it. LTG :)
Use IRL540's -- these are rated at 26 amps.
The 20N10L's were rated 20 amps. 20N10L's were obsoleted and replaced with
22NE10L's. The 22NE10L's are rated 22 amps.
http://www.greatplainselectronics.com/products.asp?cat=17

Post by Lloyd Olson
Ed at Great Plains sells a better transistor for that. It's been posted
before. I stuck one in my LOTR way back and no problems since. LTG :)

Post by Sonic
Sonic here, posting for a friend that just bought his first pin -
LOTR,

and

Post by Sonic
sure enough F20 has blown
I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there

was

Post by Lloyd Olson
a

Post by Sonic
definitive solution. And it seems that Stern hasn't really issued a

Service

Post by Sonic
Bulletin regarding this (well other than in 2004 - which is really lame)

or

Post by Sonic
has Stern fixed it themselves (surprise, surprise).
At Q6, it appears that when Stern went from a 20A transistor to a 22A,

the

Post by Lloyd Olson

Post by Sonic
problems became less frequent, but did not go away. So am I correct in

that

Post by Sonic
the fix is to replace Q6 with an IRL540 (the higher current MOSFET).

Does

Post by Lloyd Olson

Post by Sonic
that truly fix the problem ,or is that solution coupled with a change in
fuse value?
matt

[GPE]

Stern changed from a 20 amp to a 22 amp MOSFET because ST Microelectronics
quit making the 20 amp part and replaced it with the 22 amp part.... no
other real reason to it.

You may try an IRL540 as it has a 28 amp rating. Bad news -- one of the two
manufacturers (Fairchild Semi) of IRL540's has now issued a last time buy
for these parts.... another part is biting the dust.

But, I really doubt it's the current that's killing these. Often it's the
di/dt or rapid current change that kills MOSFETs. This is why you will
quite often see small ceramic caps at the gate of these caps -- to slow down
the turn on speed.

-- Ed

Post by Sonic
Sonic here, posting for a friend that just bought his first pin - LOTR,
and sure enough F20 has blown
I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there was
a definitive solution. And it seems that Stern hasn't really issued a
Service Bulletin regarding this (well other than in 2004 - which is really
lame) or has Stern fixed it themselves (surprise, surprise).
At Q6, it appears that when Stern went from a 20A transistor to a 22A, the
problems became less frequent, but did not go away. So am I correct in
that the fix is to replace Q6 with an IRL540 (the higher current MOSFET).
Does that truly fix the problem ,or is that solution coupled with a change
in fuse value?
matt

[Sonic]

Thanks Ed/Lloyd (as always).

Is the rapid current change causing premature fatigue then causing the fuse
(sometimes the transistor) to blow? And how would the higher current MOSFET
remedy that problem? Is it that the problem runs deeper, like with the
opto's in the ring magnet assembly as the source of the rapid change? Or
perhaps a cap is necessary at the gate? Just wanting to dig deeper...

Post by GPE
Stern changed from a 20 amp to a 22 amp MOSFET because ST Microelectronics
quit making the 20 amp part and replaced it with the 22 amp part.... no
other real reason to it.
You may try an IRL540 as it has a 28 amp rating. Bad news -- one of the
two manufacturers (Fairchild Semi) of IRL540's has now issued a last time
buy for these parts.... another part is biting the dust.
But, I really doubt it's the current that's killing these. Often it's the
di/dt or rapid current change that kills MOSFETs. This is why you will
quite often see small ceramic caps at the gate of these caps -- to slow
down the turn on speed.
-- Ed

Post by Sonic
Sonic here, posting for a friend that just bought his first pin - LOTR,
and sure enough F20 has blown
I've perused as much info as I could find regarding this subject, and
although a fairly common problem it seems - I didn't quite feel there was
a definitive solution. And it seems that Stern hasn't really issued a
Service Bulletin regarding this (well other than in 2004 - which is
really lame) or has Stern fixed it themselves (surprise, surprise).
At Q6, it appears that when Stern went from a 20A transistor to a 22A,
the problems became less frequent, but did not go away. So am I correct
in that the fix is to replace Q6 with an IRL540 (the higher current
MOSFET). Does that truly fix the problem ,or is that solution coupled
with a change in fuse value?
matt

[GPE]

This post might be inappropriate. Click to display it.

[Lloyd Olson]

Mine is working fine in commercial use. That is where I stop digging. LTG :)

Post by Sonic
Thanks Ed/Lloyd (as always).
Is the rapid current change causing premature fatigue then causing the fuse
(sometimes the transistor) to blow? And how would the higher current MOSFET
remedy that problem? Is it that the problem runs deeper, like with the
opto's in the ring magnet assembly as the source of the rapid change? Or
perhaps a cap is necessary at the gate? Just wanting to dig deeper...

[frenchy]

Mine blew after a year (last week) and I replaced it with a 5A and is
working fine again. Did I do something wrong?

[P***@gmail.com]

I've taken some measurements on mine because it blew the fuse after
only an hour out of the box. I found that if a ball made the spinner
and did not make the magnet ring properly the current was pretty high.
If the ball makes the magnet it seemed to be relatively average current
for the device. I spoke with the guys at Stern for some theory and
then I time-trapped the entire process on Fluke software and looked at
it pretty closely. It was the only thing that made any sense at the
time.

It's a preliminary conclusion but I think this is what is stressing the
original parts. Eventually the fuse will fail, as it gets heated each
time the ring is activated. This is why the larger fuse and higher
power transistor works.

My 2 cents. FWIW.

Mario
Pinthetic

[frenchy]

Doesn't the magnet switch to a quick pulsing once the ball is held?
The way the ball jiggles around a little makes it look like that's
what's happening. It also seems like the magnet is turned on full for
less than a second if just the spinner is hit, so that probably doesn't
do much heat cycling to the fuse (?)

[P***@gmail.com]

Read service bulletin 151 and notice how they changed the software to
allow the magnet to operate differently than it did originally. The
whole idea is that the magnet was operating at full bore when it did
not need to. This caused heat, and heat is what fatigues a fuse.

Mario
Pinthetic

[Sonic]

So would everyone agree that the fix is to replace the 4A SB with a 5A SB
(if just the fuse blows) and/or replace Q6 with the higher current IRL540 if
it's toast. Probably could throw in Black Knight's earlier post regarding
the opto alignment (to limit pulsing) in the magnet assembly too.

Seems like Stern obviously still has an issue that needs their attention.
I'm curious if putting in the higher current tolerant components will cause
trace problems on th PCB or other places in the game. But since nobody else
seems to have any other problems after the fixes mentioned above..I guess
not.....

Matt

[frenchy]

<<Read service bulletin 151 and notice how they changed the software to

allow the magnet to operate differently than it did originally.>>

I have the latest version, guess that's why the fuse lasted a whole
year : )

[Lloyd Olson]

Working fine, don't smell smoke. I'd think you are fine. And your game is
too. LTG :)

Post by frenchy
Mine blew after a year (last week) and I replaced it with a 5A and is
working fine again. Did I do something wrong?

[Peter K]

My fuse bles and I replaced it with those slow blows with the beads.
It blew again 3 games later. I replaced it with the slow blow fuses
that have the nylon wrapped around the wire and haven't had a problem
since. I also put a small TO-220 heatsink on the MOSFet and have yet
to have a problem.