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XS series issues


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#1 awhulett

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Posted 21 July 2013 - 05:31 PM

Hello.  I have an xs500 amp that had a couple shorted transistors in it, T215, TR221

I replaced the faulty parts and all 8 output transistors, TR220, 221, 222, 223, 216, 217, 218, 219 ( i found found this to be best practice for reliability to change them all)

So apparently i missed something major cause upon power up TR215 exploded and the following components had a meltdown: TR213, 211, 210, 214. D209, 215, 214. R229, 227, 260, and 224.

Diodes 215, and 214 seemed ok before applied power.


Any ideas what i did wrong here?

Also i have an xs900 that had a shorted IRF540N in it and i can't seem to find the problem with it either.

#2 awhulett

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Posted 30 July 2013 - 07:23 PM

counterfeit transistors turned out to be the problem..

#3 joust

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Posted 01 August 2013 - 10:07 AM

Guys (and that includes you, awhulett :)),
There is always a good reason to purchase parts through a responsible and reputable outlet (Crown authorized dealer). Most Crown replacement parts are reliable and have been tested and graded (ie. for power transistors) so that parts and circuits mesh well with each other. I agree that in most situations, a part from a jobber will do the trick. But falsified/counterfeit transistors? (Who does that??) I HIGHLY recommend to choose genuine Crown replacement parts for those tight and precise operating circuits.

Alain



#4 awhulett

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Posted 31 August 2013 - 10:28 PM

Well....So now i have 2 XS1200s in the lab... One i acquired with a DC offset greater than -30v  , the other had a shorted output device, Shorted fet replaced the output devices, driver, and pre driver and fet.  Short is gone.... Nasty DC Offset greater than -65v, both amps this is only related to channel 1. I cant find anything that indicates a short.. Any thoughts?

#5 joust

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Posted 03 September 2013 - 11:50 AM

I have seen some pretty high resistors (>= 1Mohm) in the driver circuit that sometimes open up! This could cause some hard to find issues. Since the output reads some quite high DC value, it is probable that the high side is clamped hard, perhaps an open resistor, diode or tranny.

Alain

#6 awhulett

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Posted 05 September 2013 - 08:53 PM

It's definitely something open. I think it may be sticking one bank of outputs to ht also. Thanks for the reply and info. I will definetly check those out.

#7 awhulett

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Posted 10 September 2013 - 06:36 PM

Well You were correct, i had a 1 mohm that had grown to about 1.8 mohm.  replaced.. set bias..soaked in..

#8 joust

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Posted 11 September 2013 - 08:35 AM

Hurrah! Good work! :)

Alain