Bang and Olufsen 609k stereo se el84 fm tuner
advice needed by a near beginner on this restoration project.
Looking for a schematic for this amp or something similar.
Hoping for some suggestions on troubleshooting
Removed insect wings and plant seeds!, cleaned, recapped and replaced way out of spec resistors. Fixed non functioning switch (with the help of my daughter), revalved. Without valves, turned on at 110v and measured voltages to check they were a, present b, in the right range. Replaced valves and turned on at 220v.
One channel working, one channel working intermittently then dying and being replaced by a variety of noises (in both channels?) pops hisses, noisiness, increasing in intensity. Turned off. My first thought was that it might be the selenium/germanium? rectifier but, I presume, that would affect both channels so now I'm thinking problems with a resistor in the power amp or preamp.
I don't have a schematic but the power amp has one ecc83, half per channel and one el84 per channel and the resistors are, per channel; 22k, 1000k, 2.1k, 470k, 470k, 1k, 410R, and 150R.
If I can get it working and the tuner section is working in stereo, I'm hoping to use that to help to diagnose a non working channel in a separate but identical tuner only that I also have!!!
You could try
UK Vintage Radio Repair and Restoration forum
Thanks for the suggestion.
I checked voltages again yesterday and think they're all too high on 220 mains voltage. Works quietly on one channel with 110v mains voltage but there is no voltage selector on the tuner itself as far as I can see and measured voltages around output are too low anyway. Also found voltage (2v) on working channel 150R resistor and associated capacitor but absent on corresponding components on other channel. Looks like there are at least two problems. One to do with power supply voltage and the other to do with signal on non working channel.
If you do not find one so I can send an e-mail.
You can respond to my email address firstname.lastname@example.org if you want the diagram (schematic).
I would almost certainly think that it is interstage coupling Capacitors becoming Leaky.
If I were you I would go through the whole circuit and replace all Capacitors, especially Electrolytics. At this age they are almost certainly 'worn' out!
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