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Old 30th Nov 2022, 11:35 am   #4
PaulR
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Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 3,221
Default Re: Cossor 524 rustling noise on FM

Thank you, both, for the replies.

After some further investigation it appears that the rustling is on both FM and AM. I thought it was just FM because that is the clearest signal. I applied an FM signal to the grids of both V2 and V3 with the previous valves pulled and the noise was still there. I also put a 470 KHz signal into the AM aerial sockets and the noise was there as well. It appears to be superimposed on the signal as it is much stronger when there is a strong signal.

I can hear it faintly with no signal as the valves are pulled up to the EABC80 which, of course, removes the pre amp AF.

There isn't a switch as such for Gram. You remove a jumper to disconnect the radio section and then use the PU sockets. I think you are intended to replace the jumper is such a way as to short the output from the radio section. Anyway, the rustling disappears when the jumper is removed. I haven only touched the PU sockets rather than put a proper signal into them but there is no rusting along with the hum.

The HT is switched but on a sliding switch rather than the wafer switch.
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