I am restoring a valve radio at the moment. The problem is it will only tune one station and that is 612 ABC. Is this an oscillator problem or should I be looking for something else. The radio tunes the one station irrespective of the position of the tuning condenser. The mixer valve is an AK2. bowler

Looks like the station is very close to you, and strong.
Getting straight into the IF amplifier.
So, does not need an oscillator or tuning gang function.
I would start with an IF alignment, as 612 kHz is very close to the IF frequency.
And perhaps some monkey has peaked the IF to the station, Oh no.....
JJ

It would be useful to know what it is? As a generalisation if it has a dead oscillator, or perhaps IF, If there is an AGC then it is quite normal for a weak un-tunable signal, from the strongest station to get to the second detector (detector /first audio) and be heard.

In order to do an IF alignment you preferably, need a Signal Generator and the information telling you the IF frequency.

If you know the IF frequency e.g. 175kHz or around but not necessarily 455kHz with the latter sets, you can use a transistor radio in close proximity to the oscillator, to see if you can pick it up.

It will normally be the IF frequency above the radio station frequency E.g 1000 + 455= 1455. Also check the oscillator gang for bent rotor vanes shorting; Outside ones being particularly vulnerable.

One hopes some Monkey has not been stuffing around with adjustments, which I find, not uncommon.

Without the IF frequency, things will be a lot more difficult. Check the voltages around the AK2 and as best, as resistances. Most of those tubes love voltage. Philips "P" base can have corrosion issues clean the base & socket. Be careful with those Metallised tubes. If the base and envelope become lose, you can break the wire that grounds to pin one (shield)

AK2 Octode: Heater 4V pins 2&3; Pin 8, Anode 250V; Pin 5, Grid 2 Screen 70V (Philips data)

445kHz 2nd harmonic 910kHz; 175kHz third harmonic 525kHz

If its got waxed paper caps and tired electrolytic caps, that will also, not help matters.

More info required.

I know where his location is, I have been to that town, and it's a fair distance from the Brisbane transmitters.

So, rather than the signal brute-forcing its way through, perhaps just an ordinary fault or misalignment.

It would help if we knew what radio model it is, and what other valves are in it.

I've only seen one AK2 before, and it turned out to be faulty.



EDIT: If your radio has a bandswitch (for shortwave for example), flick it up and down through the bands. I suggest this because I tried out a number of my radios recently, and every one with a bandswitch did weird things until the switch was flicked back and forth a bit.

Hi All, finally got back to the problem of receiving one station only. A close inspection of the oscillator coil revealed a very fine broken wire, after some tricky microsurgery the wire was rejoined, and the radio is now working. Thanks to all for their replies.