This radio was listed with a faulty tuner and when I received it the tuner needle would only move about an inch back and forth at the far right end of the scale. I took her apart and managed to get the needle moving up and down the dial again but it refuses to pick up any other stations. When it does pick this station up the FM stereo LED lights up and it tunes in nicely.

It's almost like mechanism that actually scans the frequencies is only moving that inch or so, regardless of what the tuner string is doing with the needle.

This radio looked like it was taken out of the box when it was bought and put on a shelf in a workshop where it stayed for the last 20 years until it went on ebay. Very dirty and lots of buttons/functions had 'fused' over time. But contact cleaner and lots of regular cleaning has resurrected it entirely apart from this tuner issue, as evidenced below:



Has anyone encountered this before? Is there a pot I can be pointed to that will adjust the frequency? Or is there an internal part of the assembly that could be fused and is preventing it from scanning properly?

I'd really appreciate any help, loving the sound of this radio a lot and would really love to get her back up to 100%.

Well, some further study has revealed that the tuning component on the pcb (square box with 4 adjustment screws on top) isn't registering the winder movement. It was very unwilling to move but some gentle help and lots of contact cleaner has got it moving, but it's not apparently doing it's job inside the square box.

I can adjust the screws on top, which I imagine is used to get the tuner needle in sync with the FM band, and it'll pick up stations nicely in stereo. But the dealy the winder connects to in there won't have a bar of it.

Should I look at replacing the tuner board (I DO believe in unicorns!)? Or is there another way to get this one going?



Rock On.

I pretty much have the same problem as you. My Rising has the same box with 4 screws. I finally found that one is the tuner and another is a fine tuner. However, two screws apparently do nothing at all. What's even more mindboggling is that tuning from left to right 88-108 tunes perfectly. Once I get to the end (108) and go back the other way, the tuning is off by about 4 MHz. WTF?

That's a fantastic cleaning job by the way!!

i have had that problem before but have found some of the other tuning caps ie the different color ones and some small pot unless you what to look for and know which ones are for the am or the fm or even for the sw--

The little box is called a PolyVariCon. It's a tuning capacitor with small sheets of vinyl between the rotor plates.

The four screws are paired--one set of two for AM, the other for FM. One screw adjusts the oscillator (where the station will land on the dial), the other adjusts the antenna sensitivity.

If the cap is moving freely and you're still not getting the dial to track, you might check where the cap attaches to the tuning wheel. There should be a setscrew to hold it in place. If it's loose, there will be play and the two won't track together.

Hey Batterymaker....how can you tell which one is the exact screw for its function on the tuning cap.?I need to adjust the screw that controls only the pointer and landing spot for the station that is printed on the tuning scale on my Panasonic RX-5085. Everything else seems fine and the stations don't oscillate or drift, but its off somewhat and the stations on the high end (like anything after 106.7 FM, I cannot get because I bottom out on the tuner string. Sorry to hijack, but this is interesting info! Thanks!

Short of a schematic, put the box on AM, then tweak one of the screws slightly. You'll either shift the station, increase/decrease sensitivity, or nothing at all. If nothing at all, you've found one of the FM trimmers. Draw it out on a sheet of paper and label that screw. Then do the next of the four. When you've found the FM trimmers, switch over to FM and adjust accordingly.

Well after removing the plastic cover of the PolyVariCon I've come to the conclusion that this is possibly the reason why it's not working:



Side View:



I've no idea how that could happen with the the very limited amount of travel the vinyl has to move, possibly something corrosive got in there and played merry hell with them.

So it looks like I'll be needing a new M-70 tuner pcb, unless I can replace the PolyVariCon? Is it possible to do this without a lot of expert knowledge? It looks like it just attaches to the pcb via 4 solder points...seems all pretty self contained.

It's part number QAP 1224 511V 8128, just incase someone has a cache of them lying around doing nothing.



Rock On.

That...is pooched.

You need to look for a parts set.