diytube.com

I've repaired and tuned many tubed radios, but not a transistorized tuner.


(It's the only schematic I could find. It's kinda hard to read. Hit the magnifier to slightly blow it up)

I have good AM, but no FM. Using a oscope, I have very little into IC1 (on the FM IF strip). I have:
0.1 volts out of IC1 and into the 1st filter and about 0.05 out.
0.25 volts out of IC2 and into the 2nd filter and about 0.12 out.
0.6 volts out of IC3 and through C11 to IC4, but out of C11 the modulation looks to be cut in half.
1.5 volts out of IC4 and into the discriminator/detector transformer, but with very little modulation.
0.1 volts of audio out of the detector diodes.
Ed posted a link to David Eaton's schematic of a AF-6.
http://www.davidreaton.com/Dynaco_AF6.htm

I had a shorted 120pf capacitor inside of FL52.

After getting it working I found the FM Tuned lamp out, and with it out the muting circuit would not work. I put in a 5mm blue LED with a 680ohm resistor in series and a 180ohm resistor in parallel with the LED to give enough current for the muting circuit to work. Also replaced the Stereo lamp with the LED. Hard part was finding a blue LED that looked green enough. The incandescent lamps and filter give a peak of about 490nm and the LEDs I have are from 460 to 475. 460 looks really harsh, so blue it's hard to see it. 505nm (aqua or cyan) looks too green, and mouser doesn't have a 480-490nm T1 3/4 LED. And and Radio Shack in town went out of business. And and and the hardware stores in town don't have T1 3/4 lamps.
So I have in a 475nm and called it a day.