I've been modernising this tuner with new capacitors, it sounds great but to get stereo when I switch on, I need to press it to mono, untune from the station to get static, tune back to the station then press to stereo and the stereo light comes on! Signal strength is good. I do not know where on the circuit to look? sometimes it will go mono after that by itself, but usually will stay stereo.
some of the lower rated caps I changed( e.g. 1uf) are nonpolar wima, would that be a problem? thank you.
some of the lower rated caps I changed( e.g. 1uf) are nonpolar wima, would that be a problem? thank you.
Have you changed any caps in the stereo decoder? If so, it might need realigning. Both PLL and frequency-doubler decoders need to be roughly set to the correct subcarrier frequency, so they can then lock on to the pilot tone.
you mean inside the aluminium 'box' where the gangs are? I haven't changed those. I'm thinking it's something to do with the lack of polarity on some of the capacitors I've used?
No, not RF realignment. Just the stereo decoder. Have you changed caps there? There will be either a preset pot or one or two coils with adjustable cores. Don't fiddle with them unless you have a circuit diagram or service sheet - you could easily make it worse.
One or more of those caps probably sets the subcarrier frequency. Typical caps have a 10% tolerance, which is fine for coupling etc but not for tuning - that is why there will be an adjustment. You need either a circuit diagram, or someone to pop up on here with detailed knowledge of that equipment.
Is the tuning meter perfectly centered when you tune for best sound (by ear) and maximum signal (on the meter) ? Maximum signal,undistorded sound an centered meter indication must be coincident if the tuner is well aligned. If not, I would first re-align the detector (discriminator) coil. If the discriminator is not correctly aligned stereo reception will be erratic or impossible. This is the most common problem in old analog tuners and a slight touch up (no more than a quarter turn) of the detector coil is usually all what is needed. Never touch the RF and IF coils if you don't have the right equipment and knowledge or you will end up with a totally useless tuner.
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