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Replacing Burnt Components on Gallien Krueger RB400 Bass Amp
Replacing Burnt Components on Gallien Krueger RB400 Bass Amp
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Old 15th January 2018, 03:21 AM   #11
Cheeto333 is offline Cheeto333
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So Mouser carries all of the semiconductors, except for the MJ15002. Digikey doesn't carry it either. Where's my next best option, eBay?
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Old 15th January 2018, 03:36 AM   #12
Cheeto333 is offline Cheeto333
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Do you think I can use MJ15004s in place of the MJ15002s?
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Old 15th January 2018, 04:08 AM   #13
JMFahey is offline JMFahey  Argentina
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Wait for Enzo´s answer, but I remember he usually stocks "the beefiest transistor in that class" for the very good reasons that price difference from strongest to weakest is about 1 U$ and the beefiest can replace all weaker ones, so .......
I think it was one of the MJ1502x but again, wait for him.

In any case, try to buy from Mouser or Digikey, depending on where you live Farnell might be an option.
EBay is a poker game at the sleaziest joint in town, *sometimes* you win, most often you lose.
I wouldn´t gamble with that amp repair.
***Build a lamp bulb limiter*** and always plug the amp in it, no speaker or any load yet, until all voltages check right.

Also get mica and grease for the transistors, you shouldn´t reuse the old one.
Again, no gambling.
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Old 15th January 2018, 04:14 AM   #14
Cheeto333 is offline Cheeto333
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Thanks JM. Farnell suggests the NTE61 as a replacement for the MJ15002, thoughts on the NTE61 vs. the MJ15004?
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Old 15th January 2018, 04:35 AM   #15
Enzo is offline Enzo  United States
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Yes, leave it there and order real parts. NTE are approximations at best and are NOT matches for the other transistors inside the amp. Notice also teh NTE costs $11 while teh MJ15004 costs $4.

Yes, MJ15004 is a perfect sub for the MJ15002.

Yes, I would use MJ15025 myself, but if you are ordering parts, might as well use the close one.

I have four Michelin radials on my car. If I had to replace one, I would want another Michelin radial. That NTE would be like putting on one bias ply snow tire.
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Old 15th January 2018, 04:39 AM   #16
Cheeto333 is offline Cheeto333
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Ok, thanks Enzo. I'll order some MJ15004s (as well as the other replacements) and report back when I get them swapped in.
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Old 15th January 2018, 04:44 AM   #17
Cheeto333 is offline Cheeto333
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Gah looks like the MJ15004 is on backorder (24 week lead time???), so MJ15025s it is.
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Old 15th January 2018, 05:17 AM   #18
GeorgK is offline GeorgK  Austria
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Quote:
Originally Posted by Cheeto333 View Post
Gah looks like the MJ15004 is on backorder (24 week lead time???), so MJ15025s it is.
Try Farnell, at least for Europe they are available there.
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Old 15th January 2018, 01:00 PM   #19
Kay Pirinha is online now Kay Pirinha  Germany
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If you have set your DMM to diode test mode, your measurements indicate taht all these transistors are faulty. In this case I'd check the remaining ones also.

Yes, as others said, MJ15004 is a good replacement for MJ 15002. Both share their electrical characteristics, but the xx4 withstands higher Vcb and Vce voltages. The MJ15024 is even beefier and faster and will also fit. Another option would be the MJ21194, same data as MJ15024, but extended SOAR due to it's Perforated Emitter Technology.

Best regards!
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Old 15th January 2018, 05:12 PM   #20
Cheeto333 is offline Cheeto333
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Yes, I will be replacing all the transistors in the amp. Luckily there are only a handful. I will be sure to retest each transistor once it is removed from the circuit (and test the new transistors prior to installation). If the results don't make sense, I may have to find another DMM!
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