Anybody have a source for M52472P ICs?

[David Greenland]

Hi everybody,

Just wondering if anybody knows a source in Sydney for a Mitsubishi M52472P
4-Input 3-Channel Analog Switch IC. I believe the M52470AP IC would also do
the job. I can't find it in the Wagner Electronics catalogue nor do RS
Components have a record of it. The IC is used in a video distribution box
which has one output for a television, and allows me to select between four
separate composite or S-Video inputs via four buttons on the front panel.

The data sheet is available here:
http://www.datasheets.org.uk/search.php?q=M52470&sType=part

So far I've blown two of these boxes and only just realised why. Both boxes
failed when I was plugging in my laptop computer using a standard RCA
composite connection. I just used a multimeter and measured a full 110V AC
between the RCA socket ground connections of the television and the laptop.
It seems to be similar to the zap you can get from the antenna socket on
some TV sets. Further investigation shows that the IC the switchbox uses,
the M52472P, is susceptible to transient currents. Sometimes the input or
output circuits burn out, causing either distorted output or no output at
all. I'm getting no output at all from one box, and distorted output
through Input #3 on the other box. Frustrating.

I would probably need two or three ICs, two to fix these blown boxes and one
as a spare. I'd be really grateful if somebody could suggest a supplier,
otherwise maybe I'll just see if a TV repair shop can order me a few.

Secondly, can anybody suggest a fix for this problem (apart from just not
connecting my laptop up to the box!) - I've seen RCA line isolation boxes
for sale, but they are usually used with audio gear and I don't know if
they'll work with composite video. The distribution box circuit is almost
identical to the 'Application Example' circuit shown in the PDF data sheet.
I'm not sure if changing the components to higher voltage ratings would
help, or if I need to somehow put some sort of isolator in the circuit.

Any suggestions are welcome.

Thanks!
David

 

[Phil Allison]

"David Greenland"

Hi everybody,

** Hi David ;-)

Just wondering if anybody knows a source in Sydney for a Mitsubishi
M52472P
4-Input 3-Channel Analog Switch IC. I believe the M52470AP IC would also
do
the job. I can't find it in the Wagner Electronics catalogue nor do RS
Components have a record of it. The IC is used in a video distribution
box
which has one output for a television, and allows me to select between
four
separate composite or S-Video inputs via four buttons on the front panel.

The data sheet is available here:
http://www.datasheets.org.uk/search.php?q=M52470&sType=part

** Can be got from on-line sources in the US - not cheap though.

So far I've blown two of these boxes and only just realised why. Both
boxes
failed when I was plugging in my laptop computer using a standard RCA
composite connection. I just used a multimeter and measured a full 110V
AC
between the RCA socket ground connections of the television and the
laptop.
It seems to be similar to the zap you can get from the antenna socket on
some TV sets. Further investigation shows that the IC the switchbox uses,
the M52472P, is susceptible to transient currents. Sometimes the input or
output circuits burn out, causing either distorted output or no output at
all. I'm getting no output at all from one box, and distorted output
through Input #3 on the other box. Frustrating.

I would probably need two or three ICs, two to fix these blown boxes and
one
as a spare. I'd be really grateful if somebody could suggest a supplier,
otherwise maybe I'll just see if a TV repair shop can order me a few.

** They get nearly all their bits from Wagners.

Secondly, can anybody suggest a fix for this problem (apart from just not
connecting my laptop up to the box!) - I've seen RCA line isolation boxes
for sale, but they are usually used with audio gear and I don't know if
they'll work with composite video. The distribution box circuit is almost
identical to the 'Application Example' circuit shown in the PDF data
sheet.
I'm not sure if changing the components to higher voltage ratings would
help, or if I need to somehow put some sort of isolator in the circuit.

** You do not say if the TV has the voltage on its signal ground or the
laptop.

If the latter - try grounding the laptop before you plug the AV stuff into
it.

Or simply leave its AC adaptor unplugged until other links are all made.




........ Phil

 

[David Greenland]

** You do not say if the TV has the voltage on its signal ground or the
laptop.

If the latter - try grounding the laptop before you plug the AV stuff into
it.

Or simply leave its AC adaptor unplugged until other links are all made.

Thanks Phil, will give it a go. The voltage appears on the signal ground of
the laptop, as you predicted, with the AC adaptor plugged in. It also
appears when a certain FireWire DVD/RW is plugged in, so I'll have to remove
both the FireWire DVD/RW and the AC adaptor before making any AV
connections.

I will still try to source a couple of the M52472P ICs because my TV is
virtually useless with only a single AV input. I just found a place in the
US where they are $6.50 each but need a minimum $50 order. My friend is
having a look for me in Korea. Components are disturbingly cheap over
there. I've already found three Korean distributors who sell the ICs and
have stock, but not sure if they have minimum orders. It may of course work
out cheaper to just buy a whole new switchbox, but who knows.

Thanks again,
Dave

 

[Phil Allison]

"David Greenland"

Thanks Phil, will give it a go. The voltage appears on the signal ground
of
the laptop, as you predicted, with the AC adaptor plugged in. It also
appears when a certain FireWire DVD/RW is plugged in, so I'll have to
remove
both the FireWire DVD/RW and the AC adaptor before making any AV
connections.

I will still try to source a couple of the M52472P ICs because my TV is
virtually useless with only a single AV input. I just found a place in
the
US where they are $6.50 each but need a minimum $50 order. My friend is
having a look for me in Korea. Components are disturbingly cheap over
there. I've already found three Korean distributors who sell the ICs and
have stock, but not sure if they have minimum orders. It may of course
work
out cheaper to just buy a whole new switchbox, but who knows.

** When ( if ?) you get some of those ICs - be wise to fit some protection
to the ins and outs of the box.

Diodes ( maybe 1N4148s) wired with reverse bias from each signal in/out
pin to the DC supply rail and ground ought to do.

Worst that can happen then is you fry a 5 cent, easily replaced part.


........ Phil

 

[David Greenland]

** When ( if ?) you get some of those ICs - be wise to fit some protection
to the ins and outs of the box.

Diodes ( maybe 1N4148s) wired with reverse bias from each signal in/out
pin to the DC supply rail and ground ought to do.

Worst that can happen then is you fry a 5 cent, easily replaced part.

I'll take your diode advice to heart. Definitely preferable to releasing
the magic smoke in an expensive IC.

I'm surprised they don't have any internal ESD protection, particularly for
a chip which is designed to be so exposed to the 'outside world' but I'm not
sure if that would protect against 110VAC zaps anyway.

Thanks again,
Dave

 

[Phil Allison]

"David Greenland"

I'll take your diode advice to heart. Definitely preferable to releasing
the magic smoke in an expensive IC.

I'm surprised they don't have any internal ESD protection, particularly
for
a chip which is designed to be so exposed to the 'outside world' but I'm
not
sure if that would protect against 110VAC zaps anyway.

** Bet ya it does.

The AC voltage you are reading with a 10 Mohm input DMM is the result of
stray ( or EMC filter) capacitance from the AC line to ground.

The available AC current is no more than about 0.5 mA - if you care to
you can test that by measuring the voltage across a 1000 ohm resistor from
the laptop to ground.

There is however a * very brief * surge when that charged capacitance first
meets up with ground - ie you might feel a tiny "bite" if your hand is wet
or sweaty.

THAT is what can kill the miniscule sized semis inside an IC - same thing
as a static discharge really.

OTOH - diodes are pretty tough, even the puny 1N4148.




...... Phil

 

[Franc Zabkar]

Just wondering if anybody knows a source in Sydney for a Mitsubishi M52472P
4-Input 3-Channel Analog Switch IC. I believe the M52470AP IC would also do
the job.

FWIW, Prime Electronics list an LMM52470AP for $11.33 inc GST (trade),
but have no stock.

- Franc Zabkar

 

[David Greenland]

FWIW, Prime Electronics list an LMM52470AP for $11.33 inc GST (trade),
but have no stock.

Thanks. I just also found a supplier called AERI in the US, they have an
Australian queries phone number on their website and according to their
online inventory they have 5404 of them in stock. Could be a good bet.
They seem to have a good range of ICs, and if their Australia outfit is OK
it could be a website worth remembering:

http://www.aeri.com/search/M52472P

I'll let you know if I have any success with them.

 

[Phil Allison]

"David Greenland"

Thanks. I just also found a supplier called AERI in the US, they have an
Australian queries phone number on their website and according to their
online inventory they have 5404 of them in stock. Could be a good bet.
They seem to have a good range of ICs, and if their Australia outfit is OK
it could be a website worth remembering:

http://www.aeri.com/search/M52472P

** Bound to have minimum purchase requirements - IME this kind of operator
supplies small manufacturers, not individual repair men.

Plus, their ilk are THE major source of reject and counterfeit
semiconductors - so beware.

Has this AV switcher got no local import agency or any spare parts
availability ?



........ Phil

 

[David Greenland]

** Bound to have minimum purchase requirements - IME this kind of operator
supplies small manufacturers, not individual repair men.

Plus, their ilk are THE major source of reject and counterfeit
semiconductors - so beware.

Has this AV switcher got no local import agency or any spare parts
availability ?

Thanks for the warning regarding AERI. Maybe they are like the RAM
salespeople at computer fairs. They have a whole bunch of RAM DIMMS sitting
on a polyester tablecloth. If you ask how much something is, they pick up
the chip then walk across the room to check the price, then wrap it up in a
normal non-esd protected plastic bag if you're stupid enough to buy
something from them. Dodgy.

The AV switcher only cost $45, it's a cheapie from China, but there's no
point buying another one if it will just burn out again. I can add some
reverse-bias protection diodes as you suggested, but it would be nice to
have a spare IC in case I bugger it up somehow. Here's what it looks like:
http://www.alvin.com.au/_upload_documents/AV-42GS.pdf

The switcher is great (when it works), it learns codes from existing
remotes. It also automatically converts between S-Video and composite. To
change to the DVD player I just hit play on the DVD remote and the switcher
selects input #3. For the VCR, hit play and it selects input #1. There are
plenty of cheaper units around with push-buttons, but that requires walking
to the other side of the room to change inputs. Why bother having a remote
at all if you still need to get up to change one little thing? There are
also other more expensive ones with their own remote control, but if there's
one thing I DON'T need it's another remote control. I already have 2x DVD
remotes, a TV, VCR, laptop, surround sound and a media box remote. I found
a universal remote that dispenses with four of these, but it has a habit of
forgetting custom codes every few weeks, and re-programming 20 different
buttons for seven devices is a pain in the *&%#. I now just use it for the
four devices that have in-built codes.