Ok, so i screwed up - now where can i get new FETs

[Buppy]

Hello,

Being a bit too eager to get listening, i unmuted my amp without the
BBM-jumpers in place. There was an immediate strikethrough on both FET-packages (on low side, on high). I unsoldered the FETs and everything seems to be running fine, so now i looking for new FETs.
I have seen that you can buy them from IRF for $3.5, BUT - there is a shipping fee of $50 which seems a bit high for two TO220 packages...

Does anyone happen to know where i can buy/get them cheaper?

Thanks

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Buppy

[Scratchy]

For which AMP, 7 or 15?

***It's so easy, everyone should be doing it***

[dweekie]

TO-220 would indicate the Amp15 I assume (IRFB4019H). Have you contacted 41hz to see if you can purchase extras?

[Buppy]

Yes, it's for the Amp15. I have asked 41hz about it, so we'll see what happens.

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Buppy

[Buppy]

Ok. I got the new FETs, but there is still something fishy going on.
One channel appears to be working fine, but the other is not. I checked the gate voltages with a scope today and there is no PWM on the silent channel gates...
VNN, VPP, 5V, V10, VN15 and the input bias are all fine and the amp goes happily into unmute when i close the jumper.

I'll guess i have to spend some more time with the scope, but it starts to feel like the chip went busted when the first FETs blew up?

--
Buppy

[Buppy]

Ok. One of the gate resistors is fried, and i guess the kind of current that does that also killed the chip. This amp is doomed to forever play in mono (which is does very well by he way...).
Guess i'll have to order a new kit when i'm done crying.



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Buppy

[krilli]

Do you reckon it's salvageable?

[Buppy]

Absolutely. I'm just not sure it's worth the effort/risk of replacing the chip. I can probably use it for a subwoofer or something instead.

It's an amazing amp by the way! I have tried it with my Scan-speak Event transmission line speakers which is a great combo! The Events are a bit weak in the high mid range which is very well compensated by the amp15 sharpness.

If only both where playing...

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Buppy

[Buppy]

Ok - Chip replaced and the amp now officially plays in stereo. Lovely powerful sound, BUT - somethings is probably wrong again.

After 10min of playing, not loud, there is a lot of things going warm/hot. The Chip and the output inductors are just above touchable. The close up bulk caps are warm, but the FETs are cold. I'll borrow a IR-temp meter from work tomorrow and get some numbers.

I'm running 80ns and 50VDC rails into 8ohm speakers.

Fishy oscillation going on, or what do you guys think?

Thanks,


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Buppy

[V-bro]

I've not experienced this ever myself, although someone who is using an AMP15 I built was... He would send it back to me for evaluation. When/if it arrives I can do some measurements and if I discover something fishy I shall report.

------X-max. can be several meters on any driver, too bad it can be done only once...------