crazy mishap

ee · 2118

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Offline ee

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on: February 09, 2017, 01:47:12 PM
I increased the hole size of one rca last week and somehow someway a sliver of al made its way to the c4s board perfectly underneath and touching  R2 300k resistor to the 2n2907a transistor. There was a quick burst of light, pop, and smell. LEDs are out on that channel and the 12at7 is lit on both sides it appears.
I will replace the transistor (both sides just to match) and the LEDs.
Does this sound like a reasonable place to start?
Thanks
Eric

Bottlehead Stereomour 2a3
Fostex FE206En in Vulcan (BIB BLH)
VPI Scout 1.1 with classic platter
Lyra Delos
Manley Chinook phono pre
Creek Destiny 2 CD
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Offline ee

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Reply #1 on: February 10, 2017, 06:46:49 AM
Lesson is dont mess with your electronics when you have the flu and temp of 102. I was getting some weird shorts were volume was cutting in and out and thought i just a had a bad solder joint. Looked all around c4s but not thorough enough.
R1 is toast literally dark brown now for that channel. I've ordered new parts and will rebuild hopefully from same board but I'm asking The Queen of all to see if there are some boards. I wanted to try the tantalum resistor in R1 anyway so this forces my hand. haha

Bottlehead Stereomour 2a3
Fostex FE206En in Vulcan (BIB BLH)
VPI Scout 1.1 with classic platter
Lyra Delos
Manley Chinook phono pre
Creek Destiny 2 CD
Audio Art Power Cables


Offline Paul Birkeland

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Reply #2 on: February 10, 2017, 01:02:30 PM
There should still be parts available for your SMR-2A3.  If possible, you might just want to order a new C4S board with associated parts, as removing components can be tough.

If I had to fix the board, I would replace the 2N2907, MJE5731A, and blown resistor, then call it good.  The LED's should be fine if they don't look obviously blown, and the 300K resistor is pretty impervious in this application.

-PB
« Last Edit: February 14, 2017, 08:19:48 AM by Caucasian Blackplate »

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline ee

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Reply #3 on: February 14, 2017, 04:18:24 AM
I did order a new board and will probably get it today. Thanks Eileen! I did also order a new round of 2N2907, MJE5731A, LM431A (i got the AIX instead of the stock ACX but just wider operating temp difference it looks like)and resistor either from Mouser  or digikey not sure which right now. I do have continuity from LED to LED. And if I am measuring correctly on the other components it looks like just the resistor blew. I'll know later today. Thank you !
Eric

Bottlehead Stereomour 2a3
Fostex FE206En in Vulcan (BIB BLH)
VPI Scout 1.1 with classic platter
Lyra Delos
Manley Chinook phono pre
Creek Destiny 2 CD
Audio Art Power Cables