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..
they seam ok though.."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
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....CPS 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
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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
There is a simple test method to test each output by measuring the voltage drop across each outputs power resistor, and comparing all the numbers to tell you which outputs are not balanced, thus telling which outputs to replace.
SoundStream used this test method to detect weakened output stages so they would catch them on repairs and replace them as needed. May I suggest you do the same in order to limit your work load and parts investment to a more reasonable level
Email me directly if you need a picture to show you how to test each resistor in circuit with the amp idling. I use it on all my amps, as the principals applied are all the same on all class A and AB amps. Its really simple, just a bit of a time-sink to perform.....
SoundStream used this test method to detect weakened output stages so they would catch them on repairs and replace them as needed. May I suggest you do the same in order to limit your work load and parts investment to a more reasonable level
Email me directly if you need a picture to show you how to test each resistor in circuit with the amp idling. I use it on all my amps, as the principals applied are all the same on all class A and AB amps. Its really simple, just a bit of a time-sink to perform.....
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