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Author Topic: Oops! Blown component on pcb  (Read 112 times)

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Offline gsharri

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Oops! Blown component on pcb
« on: December 07, 2022, 06:07:33 AM »
I have a pair of 300b Paramounts which were modified by Paul Birkeland to use a 6LU8 driver tube. I installed a pair of NOS 6LU8s and one of them was apparently damaged in shipping (tested good before shipping). The result: a flash of light and a "snapping" sound as D1 blew it's guts across the pcb mounted below the 6LU8 tube (see pic). What type of LED do I need for replacement and how do I test for proper operation? I have no schematics or manual as I purchased these used.
Thanks
Scott

Offline Paul Birkeland

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Re: Oops! Blown component on pcb
« Reply #1 on: December 07, 2022, 06:18:03 AM »
Just replacing the LED is rarely sufficient to perform this kind of repair.  Typically I would remove both LEDs (they are HLMP-6000), Q1, and Q2, then test R1 and R2 with the transistors removed to be sure they are still happy, then repopulate the board.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline gsharri

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Re: Oops! Blown component on pcb
« Reply #2 on: December 07, 2022, 07:32:41 AM »
I will do that. Thank you sir.

Offline gsharri

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Re: Oops! Blown component on pcb
« Reply #3 on: December 31, 2022, 07:46:12 AM »
What are the correct wattage ratings on R1 & R2 if they require replacing?
Thanks

Offline Paul Birkeland

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Re: Oops! Blown component on pcb
« Reply #4 on: December 31, 2022, 08:59:11 AM »
R1 can be an 1/8W part.  You'd want the 90.9 RN55D to get about the same part as what's there.  R2 is a 300K 3W PR-03 resistor.  If that's not available, the RR-03 is functionally about the same.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man