1. Home
  2. Electronics Repair
  3. URGENT: ISO IXFN55N50 MOSFET Devices -- US Supplier, Small QTY Needed

URGENT: ISO IXFN55N50 MOSFET Devices -- US Supplier, Small QTY Needed

I am repairing a QSC Powerlight 6.0 PFC amplifier and the problem is in the chopper circuit of one of the the power supplies. Q2, the IXFN55N50 Hi Perf MOSFET, an SOT-227B package device, had a rather spectacular end of life event. Fortunately the audio rack's breaker tripped before damage could spread to catastrophic damage levels.

I'm in the process of determining the health of related components, but at least one of the IXFN55N50 devices has become carbonized and one terminal welded itself to the mounting screw.

I'm in search of a supplier of this device, in the US, for small quantities for repair and maintenance purposes. Perhaps a maximum order of 8 devices, depending on price.

Who sells these devices in the US? My Googling takes me to a lot of Chinese suppliers and huge lot quantities.

If someone is familiar with a US supplier for these, I would greatly appreciate hearing from you. I'll check back here periodically. Thanks.

--

Take care,



Mark & Mary Ann Weiss



VIDEO PRODUCTION . FILM SCANNING . DVD MASTERING . AUDIO RESTORATION
Hear my Kurzweil Creations at: www.dv-clips.com/theater.htm
www.basspig.com The Bass Pig's Lair - 15,000 Watts of Driving Stereo!
Business sites at:
www.mwcomms.com
www.adventuresinanimemusic.com
-
Reply to
Mark & Mary Ann Weiss
Loading thread data ...

Check QSC's website

formatting link
IIRC. The chermatics are there.

The IXYS devices are probably not the ones originally specified and they're just 'commondity' N-ch mosfet or IGBTs most likely.

Graham

Reply to
Eeyore

The IRF FA57SA50LC should be compatible, and can be bought at Digikey

formatting link
?site=US&name=FA57SA50LC-ND

Reply to
Ole Geisler

formatting link
?site=US&name=FA57SA50LC-N D

Thanks for bringing this upgraded version to my attention. The price is considerably less than the other device, too. Since these appear in parallel pairs, I'll plan to replace its sibling when making the repair. Oddly enough, Digi-Key is out of stock on this item as well... perhaps some other supplier might have ready stock, hopefully.

Reply to
Mark & Mary Ann Weiss

they're

Already downloaded it before I bought the amps (to study the circuit topology) so I could research the build quality of the design. These amplifiers have an outstanding reliability track record, based on the many sound touring company owners I've spoken with last year, when I was deciding which amps to purchase. However, this one failed while turned on, but idling. QSC tests their amps by shorting the outputs, driving it to clipping, and blocking the air intakes and then retesting them to see if they meet spec, according to their marketing materials. So I'm hoping that this was a bad run of MOSFETs. I still often wonder why these fail when not under stressful operating conditions. Impurity in the die at manufacture (unclean cleanroom?) bad seal on the plastic case? Dendrites growing across the p-n junction over time? Another thing I noticed was the use of copper 'ribbon wire'--flat copper strapping for the hf power supply wiring to and from the main switching transformers--which was insulated with thin Kapton or similar tape. There was a section on the bottom that looked like the Kapton insulation had burned through, causing me to wonder if there was an arc between two adjacent (but touching) conductors, due to the way it was manufactured. The schematic actually calls for the IXYS devices by part number--that's where I got the p/n from. Fortunately, I killed the power before significant damage occured. Some smoke and soot around the viscinity. I washed the board as best as possible.

Reply to
Mark & Mary Ann Weiss

You can buy it at

formatting link
directly

>
Reply to
Ole Geisler

parallel

some

I got lucky. After digging through the QSCaudio web site, I discovered that they sell a power supply restoration kit, which includes ALL of the devices, plus diodes, op-amps and resistors, etc, for less than it would cost to buy four of these devices from a distributor. And I called QSC and they assure me that they can ship in 48 hours. If all goes well, the kit will arrive before the week ends. Of course, the tech there tried to talk me into sending the amplifier back to them for service, but the freight costs alone would be more than the repair cost. :-) I convinced him that it will work out fine if I do the repairs in my own shop. In a way, this amp is very similar to the circuitry and components used in the Harris SX line of AM broadcast transmitters, which I service in my radio engineering business. Only difference is that the transmitters run full tilt

100% duty cycle and run for the better part of a decade without a failure, while this amp was idling when it failed.
Reply to
Mark & Mary Ann Weiss

While I've managed to order a repair kit directly from QSC, they keep urgently pressuring me to send the amp in for recalibration.

I am replacing the chopper transistors, Q1-Q4 (Q2 is what failed) that drive the primary of the transformer and you can find this circuit on page 12 of this schematic, available from QSC's web site:

formatting link
ies/pl6.0PFC.pdf

Frankly, I don't see where this non-linear device, replacement of such, would necessitate a recalibration of the controller, since this is simply a binary (on/off) process, chopping pulstating DC off the input rectifiers and producing the initial 180KHz powerwave that gets split up and filtered on the secondary.

Are the variations among the same part number IGBT so great that a factory recalibration of the entire unit be performed, using "proprietary test equipment and procedures"?

My impression is that there is little to nothing to adjust for--I'm just replacing a switch with a new switch. Performance should be the same. Am I missing something?

-- Best Regards,

Mark A. Weiss, P.E.

formatting link
formatting link

-
Reply to
Mark & Mary Ann Weiss

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.