Anybody have a source for M52472P ICs?

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:

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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

Reply to
David Greenland
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"David Greenland"

** Hi David ;-)

** Can be got from on-line sources in the US - not cheap though.
** They get nearly all their bits from Wagners.
** 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

Reply to
Phil Allison

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

Reply to
David Greenland

"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.

....... Phil

Reply to
Phil Allison

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

Reply to
David Greenland

"David Greenland"

** 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

Reply to
Phil Allison

On Mon, 12 Mar 2007 06:42:52 +1100, David Greenland put finger to keyboard and composed:

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

- Franc Zabkar

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

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:

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

Reply to
David Greenland

"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 ?

....... Phil

Reply to
Phil Allison

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:

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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.

Reply to
David Greenland

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