It depends on the probe placement. Anything near 0 ohms indicates that the transistor is shorted or a transistor connected in parallel with the transistor is shorted.
When you remove the power supply FETs from the board, check them as shown on the transistor testing page (using the jumper wire).
When you remove the power supply FETs from the board, check them as shown on the transistor testing page (using the jumper wire).
okay so they need to be removed before testing? because from what i understood they didnt need to be removed until finding out if they were bad or not, also i kno the one is blown (pretty obvious) so i know im gonna have to replace those 6 supply transistors, but when checking the output transistors what should it read on those and also, what would be a good sub for those, the part number on those is : irfp250n and theyre q701-q704...if one is faulty do all 4 of those need to be replaced or what?
ok so i have the meter and jumper wire with gator clips, when i get home im gonna desolder all the transistors q17-q22, if all these aside from the blown one check out fine, do i need to then check output transistors or go ahead and check them too at the same time as the others?
nvm just hit me that its pointless to check q17-q22 since they all have to be replaced anyways^_^, im gonna check the output transistors tonight and if theyre bad order new ones along with new supply transistors...is that all that has to be checked? is the testing process for output transistors the same as supply transistors?
It's not pointless if 2 or more are still OK. You could remove the ones that are defective. Reinstall the ones that are still OK (at least one in each bank) and see if the amp will power up and produce clean audio. That would help you to determine if there were any other problems and may allow you to get all of the replacement parts in one order.
Test the transistors and post what you find before you attempt to power it up.
Test the transistors and post what you find before you attempt to power it up.
ohh okay so if i just remove the defective ones and reinstall the ones that are okay and wire the amp up and it powers on than i know i only have to order the number of defective ones? and what do you mean by at least on in each bank... and also is testing the output transistors the same as testing the supply transistors?
You still have to replace all 6. Their electrical parameters have to match and you're unlikely to have matched components unless they're from the same batch.
Get them tested then I'll provide more information.
Get them tested then I'll provide more information.
okay so test all the supply transistors and output transistors. correct? and i still havent figured out if output transistor testing is the same as supply transistor testing....is it the same or is there a diff way for those?
In this amp, the testing is the same but at this time, only check to confirm that they're not shorted. You can leave them in the board for that.
okay so since theyre in the board am i gonna use jumper cable or just put hte pos probe on leg 2 and neg. on leg 3 and it should read ol and when i reverse it it should read between .5 and .9.... please correct me if im wrong lol
The jumper isn't necessary when you're checking in the board or when simply checking to see if they're shorted.
The meter may not read OL in the circuit. If you still don't understand, simply post the readings you find.
ookay i dont think im doing it right....its jumping all over the place no matter where i put the probes.its sposed 2 just show u 1 number maybe a .01 jump here or there not from .589 all the way to 3.9 and back to ol then back to .49 and crazy stuff i dont understand lol...it does it on every transistor on the board so im not sure if its reading correctly...do i need to take them out or are they just all bad and all need 2 be replaced?
it reads all 0's...i think i figured it out...maybe,hopefully... here are my findings : q17-.660 q18-.660 q19-.659 q20 (the blown one) .771 q21-.655 and finally q22-.655 if these dont sound right i prolly didnt do it right lol lemme know what ya think
also just to let u know this was with diode mode (the only way i got a accurate readin) and with positive probe on leg 1 and neg probe on leg 3...hope that helps
If you got these reading with the transistors out of the board and one probe on leg 1, all are defective.
The output transistors can be checked initially in the board. You need to remove the power supply transistors from the board to check them. Use the method shown on the transistor testing page. You'll need to test with and without the jumper as described.
The output transistors can be checked initially in the board. You need to remove the power supply transistors from the board to check them. Use the method shown on the transistor testing page. You'll need to test with and without the jumper as described.
ok ill remove them when i get home from work n tst them out of the board...let ya kno what i find...thanks for all the help
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