Sanyo DC6100K Quadrophonic - FM issue

[lonnyholl]

Im back with another FM problem ..this time its the same Receiver but its a different issue!

The Receiver works normally from all sources except FM, you can hear FM stations if Volume is at max (using headphones)...signal strength tuning meter is working and shows strong station signals. It just suddenly stopped working...no hiss and no longer showing stereo illumination on any station. Is this a muting issue ? Any help again most appreciated to work this out.

The Radio has been running fine for about a week and used at least a few hours per day since the initial FM Repair (TR103 replaced).. then this happened.

[lonnyholl]

Could someone explain please if possible to me what TR105 role is in this circuit...I've noticed it is 0V at its Emitter (& accordingly 0V at TP3) , should be 1.5V according to Schematic.

[lonnyholl]

TR105 the culprit... FM working! seems Im working my way through the FM Boards Transistors

[DMcMahon]

Well done, a little strange that Q105 (driver for the FM discriminator) failed after first working, with same fault symptom as Q103.

David

[lonnyholl]

Originally Posted by DMcMahon

Well done, a little strange that Q105 (driver for the FM discriminator) failed after first working, with same fault symptom as Q103.

David

Yep thinking the same David, yeah not sure - power rails seem ok. What I was doing when the fault occurred was adjusting the record lift off point of the systems turntable tone arm, it meant that the receiver was turned off and on several times in a half hour, as to adjust you have to take the turntable off and then put back on and power up to try it out.

So maybe it was tired, maybe they are all getting tired....time will tell...if another one goes I might investigate this for any possible power spikes....one good thing is these transistors all available still locally.

[DMcMahon]

Yes maybe just age related failures, hopefully will settle down now.

David