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Line Audio Output Mod

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DBellW6AQ

Line Audio Output Mod

I'm really confused. I have a KIO3A, Rev A, C 2007. According to the Mod
instructions this board should need the resistance modification. BEFORE I
began the mod, the resistance across R19 and R20 was about 51 ohms each.
So how can I put a 51 ohm resistor in parallel with R19 and 20 and end up
with a new resistance of between 45 and 49 ohms? Thinking there might be a
flaw in my thinking somewhere, I added a leaded resistor across R20 and
sure enough, the resistance was now about 26 ohms, so I took it out.

What gives? Instructions wrong? Am I missing something? Thanks in
advance.

73, Dave
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Joe Planisky

Re: Line Audio Output Mod

Sounds like either that mod has already been done or your KIO3 board is newer than you think. IIRC the original value of R19 and R20 was 600 ohms. Adding a 51 ohm resistor in parallel gives 47 ohms. The newer boards have 51 ohm resistors in place of the 600 ohm units.

Perhaps Elecraft should add a "Does My K3 Have This Modification" section to their older mod instructions. Most of the newer mod instructions have such a section that explains how to tell if the mod has already been done.

73
--
Joe KB8AP

On Jan 19, 2011, at 3:24 PM, [hidden email] wrote:

> I'm really confused. I have a KIO3A, Rev A, C 2007. According to the Mod
> instructions this board should need the resistance modification. BEFORE I
> began the mod, the resistance across R19 and R20 was about 51 ohms each.
> So how can I put a 51 ohm resistor in parallel with R19 and 20 and end up
> with a new resistance of between 45 and 49 ohms? Thinking there might be a
> flaw in my thinking somewhere, I added a leaded resistor across R20 and
> sure enough, the resistance was now about 26 ohms, so I took it out.
>
> What gives? Instructions wrong? Am I missing something? Thanks in
> advance.
>
> 73, Dave

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Barry N1EU

Re: Line Audio Output Mod

In reply to this post by DBellW6AQ

Dave, which part of the instructions indicate your board needs the mod?

The Elecraft Web site says K3's before: "about Oct 7, 2008, about S/N 1900"

The revision marked on your board has no bearing on this. Boards needing the mod will measure 604 ohms at R19 and R20 as Joe mentioned.

73, Barry N1EU

DBellW6AQ wrote

I'm really confused. I have a KIO3A, Rev A, C 2007. According to the Mod
instructions this board should need the resistance modification. . . . .

What gives? Instructions wrong?

Don Wilhelm-4

Re: Line Audio Output Mod

Barry is correct. The Revision number printed on the board is for the
PC Board layout itself, and has little relationship to the version of
the populated board. This is not an "Elecraft only" situation, it is
common in the industry. This is quite common with computer option cards
as well, especially video cards.

Now, if there is a paper sticker on the board, it will usually convey
the level of the assembled board.

Bottom line - do not depend on the markings on the board for level
identification without further manufacturer's substantiation that the
markings on the board do indeed identify the level.

73,
Don W3FPR

On 1/19/2011 8:39 PM, Barry N1EU wrote:

> Dave, which part of the instructions indicate your board needs the mod?
>
> The Elecraft Web site says K3's before: "about Oct 7, 2008, about S/N 1900"
>
> The revision marked on your board has no bearing on this. Boards needing
> the mod will measure 604 ohms at R19 and R20 as Joe mentioned.
>
> 73, Barry N1EU
>
>
> DBellW6AQ wrote:
>> I'm really confused. I have a KIO3A, Rev A, C 2007. According to the
>> Mod
>> instructions this board should need the resistance modification. . . . .
>>
>> What gives? Instructions wrong?
>>