B&K AV5000 help needed

[Ardvaark]

Hi all, just acquired a supposedly working B&K AV5000 5 channel amp. Channel one has a visually blown mosfet and produces distorted sound.
K1058 on the heatsink is the offender. Any ideas on a replacement? Are these matched, 4 per channel? I can only find a schematic online with no bias or offset listings on it.

Should I just pull the rail fuses and be happy with the other 4 channels?

Thank you
Peter

[nigelwright7557]

A quick test would be to pull the faulty MOSFET and see if the amp sounds OK if it is a multi pair mosfet output stage.
Not sure if this is a lateral mosfet but if it isnt then you could try an iRFP240.

[Ardvaark]

It does have 4 outputs per channel , the K1058 and J162. 2 of each, I believe they are lateral types. Plastic packages though, not T03.

[nigelwright7557]

Check the mosfets from drain to source for shorts.
The middle pin is drain and the right hand pin is the source.
If there is just one faulty you can then remove it and try the amp again.
If it then works ok then the driver stage is probably ok and the one mosfet just needs replacing.

[Ardvaark]

Originally Posted by nigelwright7557

Check the mosfets from drain to source for shorts.
The middle pin is drain and the right hand pin is the source.
If there is just one faulty you can then remove it and try the amp again.
If it then works ok then the driver stage is probably ok and the one mosfet just needs replacing.

Great news! Thank you. Any idea where I could find another K1058?
I do know the one is bad because there is a chunk blown out of it. I'll test the others.

[nigelwright7557]

Originally Posted by Ardvaark

Great news! Thank you. Any idea where I could find another K1058?
I do know the one is bad because there is a chunk blown out of it. I'll test the others.

Loads on ebay. The full code is 2SK1058.

[Ardvaark]

Thank you for that. I do not care for Ebay or PayPal. Stopped using them awhile ago. Futerlec seems to have them, I'll order from them. So, if the others in that channel test fine then I just pop em in and go? No matching or anything? I cannot find the bias or offset settings on the net or in the schematic. Although they are two pots per channel so I'll assume those are for the adjustments. Sheesh, the caps in this things are the size of coke cans, 4 of them..

Thanks for your help.

Peter

[nigelwright7557]

Originally Posted by Ardvaark

Thank you for that. I do not care for Ebay or PayPal. Stopped using them awhile ago. Futerlec seems to have them, I'll order from them. So, if the others in that channel test fine then I just pop em in and go? No matching or anything? I cannot find the bias or offset settings on the net or in the schematic. Although they are two pots per channel so I'll assume those are for the adjustments. Sheesh, the caps in this things are the size of coke cans, 4 of them..

Thanks for your help.

Peter

If the others test fine then it should be ok to replace the one faulty one.
You really need the set up instructions to alter the pots.

[Ardvaark]

Originally Posted by nigelwright7557

If the others test fine then it should be ok to replace the one faulty one.
You really need the set up instructions to alter the pots.

Yes, the adjustments need to be made. I'll poke around on the good channels and see if I can find some test points, should not be that hard. Then I'll just copy the readings to the new channel. Yes?

Peter

[nigelwright7557]

Originally Posted by Ardvaark

Yes, the adjustments need to be made. I'll poke around on the good channels and see if I can find some test points, should not be that hard. Then I'll just copy the readings to the new channel. Yes?

Peter

I wouldnt touch the pots without instructions.
The mosfets on the other channel might need a different setting depending on their characteristics.