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Doug Self Preamp from Linear Audio #5
Doug Self Preamp from Linear Audio #5
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Old 8th September 2021, 01:30 AM   #1821
glenv6 is online now glenv6  United States
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Quote:
Originally Posted by Carl_Huff View Post
glenv6,

Here is a rear panel layout for a 1U case. I cannot remember who sent it to me, so thank you whoever you are.

Dropbox - REAR_PANEL_1U.fpd - Simplify your life
Thanks Carl!
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Old 8th September 2021, 01:32 AM   #1822
glenv6 is online now glenv6  United States
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Originally Posted by still4given View Post
Appreciate that, thanks!
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Old 12th September 2021, 02:44 PM   #1823
Johnny Canuck is offline Johnny Canuck  Canada
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Doug Self Preamp from Linear Audio #5
Default Enhanced I/O help please

Wondering if anyone else has encountered this or can provide guidance.
I think (?) I have the latest version of Carl's IO board (has the signal diodes on top, just below the relays).
I am consistently getting 14.8 V downstream from the 12V regulator (17V at the input), and just a bit over 15V across the 1N4148.
It seems like the regulator is damaged, but is there anything else to consider before changing it?

Thanks.
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Old 13th September 2021, 11:40 AM   #1824
paulf is offline paulf  United Kingdom
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Hi Johnny - there was some discussion about the 78L12 possibly being unstable without caps on the input and output side - starting around post #1058, here:

Doug Self Preamp from Linear Audio #5

There are some recommendations in the following threads about adding caps, and values to use. I think put the caps from the App note (TI?) on the underside of the board.

PaulF
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Old 13th September 2021, 12:43 PM   #1825
Johnny Canuck is offline Johnny Canuck  Canada
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Doug Self Preamp from Linear Audio #5
Thanks very much Paulf.
I'll check for oscillation - the smd caps look like a simple solution.

Cheers!
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Old 13th September 2021, 01:29 PM   #1826
fvzeppelin is offline fvzeppelin  Germany
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Soldering a small tht tantalum on the bottom side is as easy.
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Old 13th September 2021, 08:19 PM   #1827
Carl_Huff is offline Carl_Huff  United States
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PLEASE NOTE: The latest IO PCBs have a place for a decoupling capacitor. It is circled in red immediately behind the 12 volt regulator.
Attached Images
File Type: jpg PIC_IO_BOARD.jpg (50.2 KB, 212 views)
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Old 13th September 2021, 08:38 PM   #1828
glenv6 is online now glenv6  United States
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Originally Posted by Johnny Canuck View Post
Thanks very much Paulf.
I'll check for oscillation - the smd caps look like a simple solution.

Cheers!

If it helps, here is the one I used..

TAP226K035CCS
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Old 14th September 2021, 01:22 AM   #1829
Johnny Canuck is offline Johnny Canuck  Canada
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Doug Self Preamp from Linear Audio #5
Quote:
Originally Posted by fvzeppelin View Post
Soldering a small tht tantalum on the bottom side is as easy.
Thanks fvzeppelin, that's a good idea and easier to find something close to TI's indicated capacitance.

Quote:
Originally Posted by Carl_Huff View Post
PLEASE NOTE: The latest IO PCBs have a place for a decoupling capacitor. It is circled in red immediately behind the 12 volt regulator.
Thanks Carl, my board doesn't have space for a decoupling cap so I guess not quite the latest version.

Quote:
Originally Posted by glenv6 View Post
If it helps, here is the one I used..
TAP226K035CCS
Thanks glenv6 - that's a good selection. Question though, is there a reason to use 22 uF rather than 10uF, or did you just have this value in your parts box?
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Old 15th September 2021, 02:39 AM   #1830
Johnny Canuck is offline Johnny Canuck  Canada
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Doug Self Preamp from Linear Audio #5
Just an update - 10uF across the output and 0.1uF across the input and the reg is stable at 11.8 V (happened to have some SMD pieces in my parts box).
Thanks to all for pointing me in the right direction.
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