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K3 line in, line out transformers.

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Larry Lopez

K3 line in, line out transformers.

This post was updated on .

The K3 has isolation transformers for the line input (mono),
and line output L and line output R (stereo).

There are 3 sets of 2 transformers.

In each set, the circuit diagrams shows the transformers
in parallel with opposed phase.

Please see the K3 Circuit diagram KIO3 Main Sheet 2,
top left quadrant.

one of each pair is labeled TTC-108 600 ohm line transformer 1.5 KV isolation,
the other of each pair is labeled LM-NP-1001 600 ohm line transformer, 6.5 KV isolation.

I'm going to take a stab at explaining this.
I bet only one transformer of the pair is actually installed
depending on availability or local laws or something like that.

I would prefer the 6.5KV isolation ones.

I mean bucking transformers would up be a way of
measuring the leakage inductance from the primary to the secondary.
That would just be plain weird.

Larry

Don Wilhelm-4

Re: K3 line in, line out transformers.

Larry,

Note that there are only 3 transformers physically on the KIO3 board
(not 6). So only one is used of each pair shown on the schematic. Note
that one set is labeled as "ALT" meaning alternative.
For that application, the phase is not critical, except that the stereo
channels must match.
Why it is represented that way on the schematic, only the designer can
answer. I am certain it has something to do with the schematic to board
layout program that was used.

73,
Don W3FPR

On 4/8/2014 8:51 AM, Larry Lopez wrote:

> The K3 has isolation transformers for the line input (mono),
> and line output L and line output R (stereo).
>
> There are 3 sets of 2 transformers.
>
> In each set, the circuit diagrams shows the transformers
> in parallel with opposed phase.
>
> Please see the K3 Circuit diagram KIO3 Main Sheet 2,
> top left quadrant.
>
> one of each pair is labeled TTC-108 600 ohm line transformer 1.5 KV
> isolation,
> the other of each pair is labeled LM-NP-1001 600 ohm line transformer, 6.5
> KV isolation.
>
> I'm going to take a stab at explaining this.
> I bet only one transformer or the pair is actually used.
>
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K3-line-in-line-out-transformers-tp7586831.html
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Josh Fiden

Re: K3 line in, line out transformers.

These transformers don't have an industry standard form factor and
pinout. Therefore it is standard practice to place pads on the PCB which
mate parts from multiple suppliers. It's smart engineering to avoid
being locked into sole sourced components.

Those transformers called out are made by Tamura and Shinholm (marketed
by Bourns). Both make high quality transformers.

73,
Josh W6XU

>
> On 4/8/2014 8:51 AM, Larry Lopez wrote:
>> The K3 has isolation transformers for the line input (mono),
>> and line output L and line output R (stereo).
>>
>> There are 3 sets of 2 transformers.
>>
>> In each set, the circuit diagrams shows the transformers
>> in parallel with opposed phase.
>>
>> Please see the K3 Circuit diagram KIO3 Main Sheet 2,
>> top left quadrant.
>>
>> one of each pair is labeled TTC-108 600 ohm line transformer 1.5 KV
>> isolation,
>> the other of each pair is labeled LM-NP-1001 600 ohm line
>> transformer, 6.5
>> KV isolation.
>>
>> I'm going to take a stab at explaining this.
>> I bet only one transformer or the pair is actually used.