Help w/ Troubleshooting FM

Tom7227 · 14th August 2008, 04:06 PM

Hi folks,

To say the least, AM/Fm..and any RF repairs have not been my Forte.

I have a classic Yamaha Cr-1020 reciever with no FM. (AM works)

I have the schematic, so that makes it a bit easier.

The problems seem to be in the actual tuning model itself. the actual capacitor/PCB unit.

Thru troubleshooting, I injected an IF signal (from another tuner) to the output of this Tuning module and I got FM stereo to work.

So I determined that the problem is in that module.

In the module, there is a 3sk45 RF amp, (replaced), an FM oscillator and a driver. All test good.

Can I measure anything with an oscilloscope?.. the FM oscillator?

dmills · 14th August 2008, 08:13 PM

I am assuming that you have checked the power supplies and the presence of the tuning voltage, if these basics are OK, then I would start by opening up the module, then tune to the bottom and top of the band and use another receiver to see if you can hear the local oscillator 10.7 Mhz away (Which side is the question, and you can make it a lot more obvious by coupling a few millivolts of audio onto the tuning voltage)..

That should establish that the LO is working (or not), which pretty much just leaves the mixer in question.

HTH.

Regards, Dan.

14th August 2008, 04:06 PM	#1
Tom7227 diyAudio Member Join Date: Dec 2006 Location: Buffalo	Help w/ Troubleshooting FM Hi folks, To say the least, AM/Fm..and any RF repairs have not been my Forte. I have a classic Yamaha Cr-1020 reciever with no FM. (AM works) I have the schematic, so that makes it a bit easier. The problems seem to be in the actual tuning model itself. the actual capacitor/PCB unit. Thru troubleshooting, I injected an IF signal (from another tuner) to the output of this Tuning module and I got FM stereo to work. So I determined that the problem is in that module. In the module, there is a 3sk45 RF amp, (replaced), an FM oscillator and a driver. All test good. Can I measure anything with an oscilloscope?.. the FM oscillator?

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14th August 2008, 08:13 PM	#2
dmills diyAudio Member Join Date: Aug 2008	I am assuming that you have checked the power supplies and the presence of the tuning voltage, if these basics are OK, then I would start by opening up the module, then tune to the bottom and top of the band and use another receiver to see if you can hear the local oscillator 10.7 Mhz away (Which side is the question, and you can make it a lot more obvious by coupling a few millivolts of audio onto the tuning voltage).. That should establish that the LO is working (or not), which pretty much just leaves the mixer in question. HTH. Regards, Dan.