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Sony GDM-FW900 power supply MCZ3001D info needed

I have a Sony 24" GCM-FW900 monitor with a power supply that keeps shutting down. It will run for anywhere from 10 seconds to 20 or 30 minutes before shutting down.

All the voltages in the power supply look fine with no ripple. The power simply shuts off with no change in the output voltages before shutdown. I've confirmed that the power supply is at fault by swapping it with a known good power supply.

I've swapped all the major power supply components between the good and bad one with no change (including the MCZ3001 control IC, transformer, +220v rectifier, +12v regulator, +220v feedback reference, optoisolator, output FETs and the timing cap for the MCZ3001). All the caps test fine for ESR. All resistors measure fine. Nothing is running hot. It's not at all sensitive to vibration, or flexing of the board. I've even tried disabling the over current and over voltage protection with no change.

Does anyone know where I can find a data sheet for the MCZ3001D power supply control IC? I need to find out exactly what conditions can make it shut down. Andy Cuffe

snipped-for-privacy@gmail.com

Reply to
Andy Cuffe
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Hi Andy, All I was able to find was a schematic of a Sony KV-27FV300/29FV300/32FV300/36FV300 power supply with this chip in the middle, and an internal block diagram of the chip. If either will help (probably not), I'll send 'em to you.

Bob

Reply to
Bob Parker

Hi Andy,

The manufacturer is Shindengen

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Sadly no data sheet, it is very commonly used in Sony CRT TV's and I've even seen it used in a couple of LCD models.

As far as I remember it has three protection mechanisms:

Pin 1 is used for under voltage lockout (ac line voltage) Pin 8 (VCC) is monitored for excessive voltage. >18V rings a bell but I wouldn't swear to it Pin 9 (OCP) monitors current accross the sense resistor(s) on the primary side.I've never had much luck moitoring Pin 9 as the voltage waveform here is tiny.

Good luck fixing it.

Philip

Reply to
Electric dabbler

Thanks for the tip. I found some information a Sony training manual for a TV using the same power supply IC. It gave some good pointers, but nothing that helped in this case.

All those voltages were fine right up to and even shortly after shut down. I ties the OCP pin to ground, so that should have completely disabled OCP.

Next I replaced the two 1kV 330pF caps going from D to S on the output FETs (C641,643). So far the power supply has been running fine, but only time will tell. The same caps worked fine in the other power supply, but the stress of de-soldering could have temporarily fixed an intermittent short, or open in one of the caps.

I'm almost out of parts to replace in this thing! I'm just glad I had a working supply to swap parts with.

Interestingly, the bad supply was manufactured using lead free solder and the good one uses regular. The first thing I did was to re-solder pretty much everything in the power supply (including the caps in question). Andy Cuffe

snipped-for-privacy@gmail.com

Reply to
Andy Cuffe

Hope you found it with the caps. I've had that thing happen to me, very annoying when the faulty component fixes itself.

Philip

Reply to
Electric dabbler

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