I have heard all iPhones do not allow use of FM radio. I have had 2 Moto Android phones that the FM Radio app worked with. I also have a brand new Samsung that supposedly works with FM also. I presume

After the power supplies, the first thing I would look at is the RF front end tuning voltage. This is a DC voltage that changes with the tuned frequency, maybe 4 volts at 88.1 to 25 volts at 107.9. Th

Most late 70s and later tuners use one or more ceramic IF filters for AM. I have found most digital tuners use an IF frequency of 450 kHz, while older analog tuners might use 455 kHz. You would need a

The + input to the op amp must a DC bias path. You can't just AC couple it with no bias. In Ray's example, the + input is DC biased to VCC/2 with two 100K resistors. If you do this, you don't need to

Be careful about the VCE voltage rating. The 2N918 is 15V, and it sounds like you have a higher voltage (18V) in your circuit. The KSP10 is 25V. If you search Mouser or Digikey and specify the VCE tha

I didn't find datasheets for those old parts, but if the part is in a TO92 package then the Onsemi KSP10 might work. A lot of thru-hole parts are going away, but Mouser has this one. Don

I think you probably want to check the AM/FM voltage switching. Q278 switches 12V on to the FM circuitry. Q279 switches is on to the AM circuitry. Do you have a solid 12V on the collector of Q278 in F

If the S out jumper is the jumper shown below that is connected to the junction of R322 and R323, then -4.4 volts there sounds like a big problem. This point would be at 0 volts when the detector is a

NEC apparently made quite quite a bit of MCS equipment. I found the following in some online discussion somewhere. I don't remember where and I can't vouch for the accuracy. List of MCS tuners made by

Great! Glad that did it. Don

IC91 is the microprocessor. One thing to look at is Q301, which is near the LA3401 multiplex chip. When this transistor turns ON, it pulls pin 16 of the LA3401 to ground thru a 47k resistor. This forc

I would check the detector zero adjustment. In the service manual, refer to "FM Mono Distortion Adjustment" step. Check DC voltage between TP12 and TP13 when tuned to a station. The procedure says to

It looks like pot VR1 sets the PLL free running frequency in the HA1196. You can adjust it using off-the-air stations. Just adjust carefully in either direction until stereo quits working, then set it

I agree 100%. It is what it is. You can't really make it equal in quality to analog FM no matter what you do. Don

I don't know exactly how it works, but you have the basic idea. My experience with the T-85 is that operating in an office building caused the display to show a low level on some local stations that a

Sorry, I don't have a schematic. Don

Find the varactor tuning voltage that goes to the front end. My guess would be that it's not covering the entire range - low voltage at 88.1 and high at 107.9. The range will be given in the service m

On Wed, Nov 24, 2021 at 10:52 PM, Don Waring wrote: I don't think connecting an antenna directly to the output of the dual gate mosfet is a valid test. You could have a blown mosfet, but I wouldn't tr

The trimmer capacitor issue is described here: https://groups.io/g/FMtuners/message/65164 Don

You have an antenna on the back of the tuner that is very sensitive to picking up RF out of the air because it feeds an RF amp. I kind of doubt the RCA cables would pick up more and inject more interf