I just imported an ALPS MD5000 printer from the USA and stupidly forgot
to plug it in to my 240110 transformer before plugging it in ...BANG
went the fuse and at least one component on the PSU board....(you get
used to everything being auto-sensing these days!).

The printer was new, but at least 5 years old (these printers are
unique in that they are capable opf printing white thanks to a unique
ribbon cartridge system), they are hard to come by and cost me quite a
bit to get here..trouble is that options for 'professional' repair here
are very limited (alps only service in the USA), which means that I am
going to have to fix it myself (I can solder and have done some
electronics in my time - mainly kit build stuff)..

Looking at the board, it seems (from visual inspection at least) that
in addition to the fuse, the next component in line (which is what I
can't identify) has also blown (I am hoping that this will be it, but
one thing at at time!).

The part is a mystery though. My guess is that it is a thermal fuse or
Transorb (not sure whether these work with AC at all). Markings on it
are 7C241 49P (with the symbol 'SA' in a circle). I have tried all the
obvious combinations (googled endlessly), but no luck.

Can anyone shed any light? As I say it is directly inline after the 4A
fuse and the marking on the board looks like a resistor, but with one
set less Squiggles (like a Z on its side). The board is marked 'Z1' for
the component (all other components are marked as ususal Cn for Caps,
Rn for resistors etc).

I have posted some images of these here :

http://users.fcpl.com/~ben/printerpsu/board.jpg

http://users.fcpl.com/~ben/printerpsu/board_back.jpg

http://users.fcpl.com/~ben/printerps..._component.jpg

Any help would be gratefully received.

wrote:

snip

Can anyone shed any light? As I say it is directly inline after the 4A
fuse and the marking on the board looks like a resistor, but with one
set less Squiggles (like a Z on its side). The board is marked 'Z1' for
the component (all other components are marked as ususal Cn for Caps,
Rn for resistors etc).

It's a 'transorb' alright. You can tell since it's connected across live and
neutral ( see the pcb tracking ).

Can't decode the part number for you but the energy rating of these is
determined largely by size anyway. Fitting a larger one won't hurt either. It
won't hurt not to have anything fitted there though for now since it only does
anything under overvoltage conditions ! Ahem ! Now do remember the
autotransformer this time !

It's just possible that it may have saved the rest. If not I'd suspect Q2 for
possible overvoltage damage. Dunno about Q1. trying to fathom the circuit from
looking at the board.

What's the component marking on Q1 and Q2 anyway ?

Do replace the fuse with exactly the same part btw. I notice that the board
doesn't state fast or slow type. If you still have the blown fuse check the end
cap. T = 'time lag' ( slow ) and F = fast.

Graham

wrote in message
oups.com...

The part is a mystery though. My guess is that it is a thermal fuse or
Transorb (not sure whether these work with AC at all). Markings on it
are 7C241 49P (with the symbol 'SA' in a circle). I have tried all the
obvious combinations (googled endlessly), but no luck.

http://en.wikipedia.org/wiki/Varistor

and much more than u wanted to know from one manu:
http://www.epcos.com/inf/70/db/var_01/00190041.pdf

The 'sa in a circle' is actually the safety designation "CSA" (Canadian
Standards Association), a certification listing like UL.

Hard to see the left logo leg, but the '7' looks like a triangle to me. It,
along with the other funky E character would be the manufacturer logo and/or
plant markings. I can't be certain about your MOV's rating, but the '241'
suggests it's a 240-volt. The '49p' may be the date code or the transient
energy joule rating (49).

Ray L. Volts wrote:
wrote in message
oups.com...

The part is a mystery though. My guess is that it is a thermal fuse or
Transorb (not sure whether these work with AC at all). Markings on it
are 7C241 49P (with the symbol 'SA' in a circle). I have tried all the
obvious combinations (googled endlessly), but no luck.

http://en.wikipedia.org/wiki/Varistor

and much more than u wanted to know from one manu:
http://www.epcos.com/inf/70/db/var_01/00190041.pdf

The 'sa in a circle' is actually the safety designation "CSA" (Canadian
Standards Association), a certification listing like UL.

Hard to see the left logo leg, but the '7' looks like a triangle to me. It,
along with the other funky E character would be the manufacturer logo and/or
plant markings. I can't be certain about your MOV's rating, but the '241'
suggests it's a 240-volt. The '49p' may be the date code or the transient
energy joule rating (49).

Great, thanks to you both for the help :-)

But of the two which should I use - a Transorb or a Varistor (it looks
to me like they are more-or-less interchangeable)?

Assuming that I can't find the actual direct replacement, can you
suggest a value for the alternative Transorb or Varistor (the fuse is
rated to 4 Amps and was quick blow by the way).

Thanks again.

wrote:

Ray L. Volts wrote:
wrote in message
oups.com...

The part is a mystery though. My guess is that it is a thermal fuse or
Transorb (not sure whether these work with AC at all). Markings on it
are 7C241 49P (with the symbol 'SA' in a circle). I have tried all the
obvious combinations (googled endlessly), but no luck.

http://en.wikipedia.org/wiki/Varistor

and much more than u wanted to know from one manu:
http://www.epcos.com/inf/70/db/var_01/00190041.pdf

The 'sa in a circle' is actually the safety designation "CSA" (Canadian
Standards Association), a certification listing like UL.

Hard to see the left logo leg, but the '7' looks like a triangle to me. It,
along with the other funky E character would be the manufacturer logo and/or
plant markings. I can't be certain about your MOV's rating, but the '241'
suggests it's a 240-volt. The '49p' may be the date code or the transient
energy joule rating (49).

Great, thanks to you both for the help :-)

But of the two which should I use - a Transorb or a Varistor (it looks
to me like they are more-or-less interchangeable)?

Transorb is simply a trade name owned by some company for varistors.

Assuming that I can't find the actual direct replacement, can you
suggest a value for the alternative Transorb or Varistor (the fuse is
rated to 4 Amps and was quick blow by the way).

Well, it's unclear if the varistor was indeed 240V. It shouldn't have blown if it
was. It might be easier to ask who you buy components from. I can point you in the
direction of Farnell but without an account the minimum order is £20 .

Remember, it won't hurt if the varistor's not there right now. It's only needed to
deal with overvoltages.

The fuse look like it was 20x5mm size and you should get one specced at 250V with
a F4A (L) current rating.

Graham

Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want? I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

am I way off?

wrote:

Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want?

That's what I was thinking. Although it seems vaguely moot now. Actually US
voltage is officially 120V btw.

I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

RS is a pain. You have to log in even to look at data and I can't even remember
our details now ! What's their problem ? Do they think someone's going to steal
their website ?

Here's a couple of candidates from Farnell ( I've assumed 130V AC )
http://uk.farnell.com/jsp/endecaSear...=1004385&N=401
http://uk.farnell.com/jsp/endecaSear...=1004282&N=401

Graham

On Mon, 15 May 2006 21:06:25 GMT, "Ray L. Volts"
put finger to keyboard and composed:


wrote in message
roups.com...

The part is a mystery though. My guess is that it is a thermal fuse or
Transorb (not sure whether these work with AC at all). Markings on it
are 7C241 49P (with the symbol 'SA' in a circle). I have tried all the
obvious combinations (googled endlessly), but no luck.

http://en.wikipedia.org/wiki/Varistor

and much more than u wanted to know from one manu:
http://www.epcos.com/inf/70/db/var_01/00190041.pdf

The 'sa in a circle' is actually the safety designation "CSA" (Canadian
Standards Association), a certification listing like UL.

Hard to see the left logo leg, but the '7' looks like a triangle to me. It,
along with the other funky E character would be the manufacturer logo and/or
plant markings. I can't be certain about your MOV's rating, but the '241'
suggests it's a 240-volt. The '49p' may be the date code or the transient
energy joule rating (49).

The "7" may indicate the MOV's diameter in mm. This in turn may be
related to its joule rating.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

wrote in message
ups.com...
Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want? I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

am I way off?


Note that the 240V mains supply is actually RMS - the peak voltage is nearer
320, which is slightly puzzling since quite a few manufacturers specify 275V
varistors! Likewise, some switchable PSUs have 150V varistors across each of
the 2 series connected reservoir caps - which often suffer from the failure
of one VDR resulting in the destruction of the capacitor across the other
VDR.

When I scrap a PC monitor, I always plunder it for any useful parts - and
varistors definately fit this category, a certain Scandinavian made monitor
had 1100V varistors in the mains filter circuit - they had a very vastly
over optimistic view of the reliability of their SMPSUs!!!

ian field wrote:

wrote in message
ups.com...
Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want? I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

am I way off?

Note that the 240V mains supply is actually RMS - the peak voltage is nearer
320, which is slightly puzzling since quite a few manufacturers specify 275V
varistors!

They normally specify by AC Volts. Hence no problem.

Graham

Pooh Bear wrote:
wrote:

Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want?

That's what I was thinking. Although it seems vaguely moot now. Actually US
voltage is officially 120V btw.

I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

RS is a pain. You have to log in even to look at data and I can't even remember
our details now ! What's their problem ? Do they think someone's going to steal
their website ?

Here's a couple of candidates from Farnell ( I've assumed 130V AC )
http://uk.farnell.com/jsp/endecaSear...=1004385&N=401
http://uk.farnell.com/jsp/endecaSear...=1004282&N=401

Graham

Thanks again Graham (and others), I've ordered the new varistors from
Farnel and will keep you posted.

One other thing was you asked abou the values on Q1 and Q2, they are :

Q1 K2972
Q2 C1741A

I can't see any damage to them, so we'll see.

Other thing that I forgot to mention. Right after it first blew, I
swapped out the fuse for a correct version, expecting it to work OK
(before I noticed the blown Varistor).

Plugging it in to the 110V supply though unexpectedly blew the fuse
again - I say unexpectedly because if the Varistor was blown already at
that point, shouldn't that have prevented a circuit to earth and a 2nd
blow fuse, or am I missing something about the way Varistors work?

thanks again :-)

wrote in message
oups.com...

Pooh Bear wrote:
wrote:

Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want?

That's what I was thinking. Although it seems vaguely moot now. Actually
US
voltage is officially 120V btw.

I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

RS is a pain. You have to log in even to look at data and I can't even
remember
our details now ! What's their problem ? Do they think someone's going to
steal
their website ?

Here's a couple of candidates from Farnell ( I've assumed 130V AC )
http://uk.farnell.com/jsp/endecaSear...=1004385&N=401
http://uk.farnell.com/jsp/endecaSear...=1004282&N=401

Graham

Thanks again Graham (and others), I've ordered the new varistors from
Farnel and will keep you posted.

One other thing was you asked abou the values on Q1 and Q2, they are :

Q1 K2972
Q2 C1741A

I can't see any damage to them, so we'll see.

Other thing that I forgot to mention. Right after it first blew, I
swapped out the fuse for a correct version, expecting it to work OK
(before I noticed the blown Varistor).

Plugging it in to the 110V supply though unexpectedly blew the fuse
again - I say unexpectedly because if the Varistor was blown already at
that point, shouldn't that have prevented a circuit to earth and a 2nd
blow fuse, or am I missing something about the way Varistors work?

thanks again :-)


You might be missing the fact that overvolting the PSU has blown the chopper
MOSFET S/C !!!!!

wrote:

Pooh Bear wrote:
wrote:

Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want?

That's what I was thinking. Although it seems vaguely moot now. Actually US
voltage is officially 120V btw.

I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

RS is a pain. You have to log in even to look at data and I can't even remember
our details now ! What's their problem ? Do they think someone's going to steal
their website ?

Here's a couple of candidates from Farnell ( I've assumed 130V AC )
http://uk.farnell.com/jsp/endecaSear...=1004385&N=401
http://uk.farnell.com/jsp/endecaSear...=1004282&N=401

Graham

Thanks again Graham (and others), I've ordered the new varistors from
Farnel and will keep you posted.

One other thing was you asked abou the values on Q1 and Q2, they are :

Q1 K2972

2SK2972 - N-channel Mosfet - 500V 10A 40W ( looks like it may have survived then ! )

Q2 C1741A

2SC1741 - NPN Bipolar transistor - 40V 0.5A 0.4W

I can't see any damage to them, so we'll see.

Other thing that I forgot to mention. Right after it first blew, I
swapped out the fuse for a correct version, expecting it to work OK
(before I noticed the blown Varistor).

Plugging it in to the 110V supply though unexpectedly blew the fuse
again - I say unexpectedly because if the Varistor was blown already at
that point, shouldn't that have prevented a circuit to earth and a 2nd
blow fuse, or am I missing something about the way Varistors work?

Not sure to be honest. I hope it failed short. You could always measure its
resistance now.

Hint - never replace a fuse before discovering why it blew.

Graham

wrote:

shouldn't that have prevented a circuit to earth and a 2nd
blow fuse

It wasn't a circuit to earth that blew the fuse, it was an overcurrent fault on the
live / neutral circuit btw. Most faults don't involve the earth connection.

Graham