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Old 24th July 2007, 05:28 AM   #1
jleaman is offline jleaman  Belgium
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Default Smoking HOT X-BoSoZ HELP!

So i'm listening to my pre-amp that has worked for a while now, and i smell this weird hot smell, i open up my pre-amp to see that 4 resistors have goten so hot that they de-soldered from the board the pre-amp is working but these babys get hot, how come ?


Pictures can be here,


Pic 1
Pic 2
Pic 3

This is upsetting, Ive spent way over 400$ on this, has eny one's done this ?

Yes the resistors are elevated. Do i now have to buy a new one ? UGG!
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Old 24th July 2007, 06:43 AM   #2
lgreen is offline lgreen  United States
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Default wow!

Hey, those resistors look pretty warm!

Even more impressive is that they look to be two 1.5K 3 watters in parallel to reduce the power consumption on each! Are they R1/R6 and R7/R2 on the X-CCS-BOSOZ schematic...as used by Kari here? If not what are they?

More importantly what voltage do you get across them and what are the PS rails? If your circ is not like the linked schematic- what schematic are you using?

Mine runs hot, but not that hot...

I'm sure this can be figured out with some more info.
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Old 24th July 2007, 09:42 AM   #3
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Default Re: Smoking HOT X-BoSoZ HELP!

Quote:
Originally posted by jleaman
So i'm listening to my pre-amp that has worked for a while now, and i smell this weird hot smell, i open up my pre-amp to see that 4 resistors have goten so hot that they de-soldered from the board the pre-amp is working but these babys get hot, how come ?


If the amp works flawless, what should be the advice, except saying that there is too large number of thru-R currents?


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Old 24th July 2007, 02:32 PM   #4
jleaman is offline jleaman  Belgium
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Default Re: wow!

Quote:
Originally posted by lgreen
Hey, those resistors look pretty warm!

Even more impressive is that they look to be two 1.5K 3 watters in parallel to reduce the power consumption on each! Are they R1/R6 and R7/R2 on the X-CCS-BOSOZ schematic...as used by Kari here? If not what are they?

More importantly what voltage do you get across them and what are the PS rails? If your circ is not like the linked schematic- what schematic are you using?

Mine runs hot, but not that hot...

I'm sure this can be figured out with some more info.

Yes they are the 1.5k @ 3w it's weird only one side of the set of resistors gets hot.
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Old 24th July 2007, 03:39 PM   #5
lykkedk is offline lykkedk  Denmark
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Maybe it's dumb, but are you sure theese two 1,5k are identical, i mean if there is something wrong with one of them, the total amount of ohm, will be very wrong

Jesper
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Old 24th July 2007, 04:18 PM   #6
lgreen is offline lgreen  United States
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Default Twisted?

what is the voltage across those resistors? How does that compare to the other channel? That's a Twisted Pear preamp right? Maybe those guys and chime in.

Looks like you have some melted capacitors too, hmm... that damage looks like a soldering iron "accident."
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Old 24th July 2007, 05:09 PM   #7
jleaman is offline jleaman  Belgium
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The capacitor is fine, i did that by accident. However this has happened to both channels, only on that one side where the resistors are, This is bizzar.

I can check the voltages later on tonight, ill have to re-solder these brown resistors in.

Any other suggestions ?
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Old 24th July 2007, 05:09 PM   #8
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I had a similar problem when I first built my xbosoz, same twisted boards.

In my case I measured a huge discrepancy between L and R channel voltages on those resistors. The "root cause" seemed to be shorting of fets. I changed the mica insulators and problem solved.

Just a newbie so be gentle if this not make any sense but I have been running my xbosoz for two weeks now no issues.

pathmark
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Old 24th July 2007, 05:21 PM   #9
Blues is offline Blues  United States
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Check that your fet screw insulators are doing their job and not shorting the Drains to chassis.

BTW, you can also improve on your soldering skills
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Old 24th July 2007, 08:01 PM   #10
jleaman is offline jleaman  Belgium
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Funny, my soldering skills rock, however it is hard to work inside this chassis, and i can guarantee you that my isolation between each fet is perfect.
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