Help with defective KFL3A-400 needed

[Marcus Busch [DL1EKC]-2]

Hello everybody,

I have a friend's KFL3A-400 on my bench which shows a 20 dB passband attenuation with
high ripple. The fault was originally detected by a 3 S units signal drop in the K3
compared to its other crystal filters. The filter was working perfectly until
recently.

I disassembled and measured all crystals and they seem to be OK, with the exception
of crystal no. 6 showing a higher ESR. But is this an issue?

The input and output transfomers seem to be OK as well, although checked only for DC
conductance and isolation. All solder joints have been checked.

These are my measurement results:

passband: http://www.dl1ekc.de/LinkedContent/DL3QQ_KFL3A-400.png
crystals: http://www.dl1ekc.de/LinkedContent/DL3QQ_KFL3A-400_Quarze.pdf

Any filter expert around here who can point me into the right direction? Any help is
greatly appreciated.

VY 73

Marcus

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[Don Wilhelm]

Marcus,

You might want to query the folks at Inrad - they build the 8 pole filters.

You would need to replace all the crystals with a matched set, so it may
be better to buy a new filter.

73,
Don W3FPR

On 12/30/2016 8:18 AM, Marcus Busch [DL1EKC] wrote:

> Hello everybody,
>
> I have a friend's KFL3A-400 on my bench which shows a 20 dB passband attenuation with
> high ripple. The fault was originally detected by a 3 S units signal drop in the K3
> compared to its other crystal filters. The filter was working perfectly until
> recently.
>
> I disassembled and measured all crystals and they seem to be OK, with the exception
> of crystal no. 6 showing a higher ESR. But is this an issue?
>
> The input and output transfomers seem to be OK as well, although checked only for DC
> conductance and isolation. All solder joints have been checked.
>

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