ndp7060 sub?

[marko]

i'm wanting to replace the psu fets in my s/s ref1000s and the schematics are showing ndp7060's but these seam a little tricky to find and the ones i just pulled out were 50n06 iirc, is the 50n06 a suitable replacement?

[Perry Babin]

If you can't find the originals, the IRFZ48V or the HUF75339P should be suitable subs.

The 50N06s are rated for significantly less current.

When they failed, did they do any damage to the circuit board?

[marko]

there's no damage to the board, just wondered why the last ech used a less rated item.

so i'll be ok with irfz48v..

[Perry Babin]

I know of no reason that the Z48V wouldn't work.

Check the gate resistors and the 2SA1562 driver transistors.

Also check the tops of the transformer and inductor winding for worn spots in the insulation. I've seen a lot of them short to the covers in these old SS amps.

[1moreamp]

Try RFP70N06 ( Harris Semi ) as a replacement also. I use these all the time, and have had very good results. NDP is a national Semi mark and as I recall National Semi no longer makes Mosfet devices going on several years now...Best of luck Marko....

[marko]

just looked up rfp70no6 on ebay they want loads for them! irfz48v's seam quite cheap in comparison, will have a look on farnell website as this is a local company to me with free shipping.

i did check the gate resisitors and they were fine but i shall go back and check the drivers.

[marko]

just got my irfz48v's and was ready to fit them then thought i would ohm the pads out where they sit, from centre pin to earth they arn't ready much like 50-100ohms steadily rising up to k's.. this doesn't seam right to me, any ideas what would cause this? all 8 gate resistors look/check out ok but the 2SA1562 drivers have been substituted for something else they seam ok though..

[1moreamp]

"from centre pin to earth they arn't ready much like 50-100ohms steadily rising up to k's.."


Your reading capacitors charging in the circuitry < usually > If the gate resistors are intact and correct and the driver transistors are OK < not shorted > Your doing OK by my experience.

And yes the RFP's are expensive at many dealers, but I managed to hoard up 4 or 500 pieces of old stock a few years back. Sorry , I forget most folks don't hoard Mosfets like I do But I don't have to look far for parts in most cases. Not like my early dazes of repairing amps....C

PS you can always test your repair by just using one mosfet on each bank, and then test firing the amp on a current limited power supply set at 5 amps max. The amp should turn on, just don't apply any load or drive signal and don't operate it any longer then need to see proper turn on and you should be Ok and get some basic turn testing out of the way before completing the repair....1 or 2 burnt mosfets are way cheaper then a whole set of mosfets......C

[marko]

thanks C, that makes sense, the amp wasn't pulling much ampage before but the amp was going into high current mode (with no load) and there was no output.. then i read the low ohms on one side of the fets so ordered new ones.

[1moreamp]

Originally Posted by marko

thanks C, that makes sense, the amp wasn't pulling much ampage before but the amp was going into high current mode (with no load) and there was no output.. then i read the low ohms on one side of the fets so ordered new ones.

High current mode at idle suggests that either the current sensing is not right or there maybe damaged channels triggering the power supply into high current mode...C