Quad FM4 tuner help and info needed

[AMV8]

I am trying to find a replacements for 2 damaged filters L17 and L18 in my Quad FM4.

Quad identify the parts as filters. They seem to be adjustable coils.
Quad give a pert number LLPFS21.
The filters have the following numbers on; 208BLR-3152N 85184

Any help locating replacements appreciated.

Don

 

[405man]

I am on holiday at the moment and wont be back for an other couple of weeks but I have a scrap FM4 so I should be able to help you out when I get back

Stuart

 

[AMV8]

Thanks, please let me know when it is convenient for you.
Don

 

[DF96]

That is probably a Toko/Murata pilot tone filter.

 

[davidsrsb]

208BLR-3152N was a Toko pilot tone filter

 

[AMV8]

Thanks for all the replies.
Davidsrsv thanks for confirming that.
Does anyone know a modern part number for the filters?
I have checked the Toko and Murata lists but I have not been able to find a modern equivalent, but this is probably due to my lack of knowledge of filters.
Don

 

[DF96]

You need to find which frequencies the filter removed (one or both of 19kHz and 38kHz), and what its matching impedance is (possibly 4.7k). Then find a modern equivalent which does the same job.

How is it that both have failed? Did you try to adjust them and break the core?

 

[davidsrsb]

You could probably bypass them. The purpose of the filter was to prevent a beating problem with cassette recorder bias oscillators

 

[DF96]

If the tuner was relying on them to remove the pilot tone then you will get a 19kHz tone at about -20dB. Most people won't hear it, but youngsters and pets might.

You need to check which chip the tuner uses for MPX stereo. Most modern chips do pilot cancellation themselves so the external filter just has to remove the 38kHz stuff.

 

[AMV8]

DF96
I was replacing the battery and the electrolytic capacitors when a friendly dog joined in and knocked the 2 filters from the pcb ( they are only loosly connected but there are lots of pcb connections per filter )
Don

 

[davidsrsb]

Some FM4s used the TCA4500a decoder, which has respectable pilot tone rejection figurs

 

[DF96]

Pets need to be kept well away when a soldering iron is hot. I am surprised that the filters came off so easily; perhaps they were not properly soldered on.

Were the electrolytics faulty too? I hope this is not going to turn out to be another one of those "I recapped it to upgrade it but now it doesn't work" sort of threads. Dogs do not usually appear in such threads.