vintelectra
Active Member
The apparently only feasible mistake could have been at the ceramics from modulator outputs to grids of matrix mixer (.02 uf). However, when comparing with a spare adapter they are ok. Martin
Patrice;Yes, this particular 6GH8 exhibits maximum separation without touching 38 kc and 19 kc coils/cans. The original one gave a reading of around 24 dB left-right and 28 dB right-left. Swapping 12AT7 also modify dramatically the results. By putting another one than the original (stronger), separation decreases under 20 dB.
Now, I have to verify if the fm transmitter really outputs 19 kc. Also, you have no advice as to what I can tweak to obtain a more equal reading as for stereo separation? 38 kc primary or secondary? Anything else. Please also note that even if stereo is easily heard, the neon pilot doesn't light at all ( yes, it's a brand new one before you ask), except sometimes between stations where there's a lot of hiss and distortion...
Anyway, it would be a temporary fix as one of the AK member here in Montréal will thoroughly align it in a month or two (once its backlog will be cleared).
Regards,
Patrice
Patrice;
Neon lamps are notorious for not firing at the same voltage every time and within a group of neon lamps (of the same type) each one will likely fire at a different voltage. I had a H-K F-50-XK tuner with such a stereo indicator. It was a kit tuner I put together myself way back in the early 1960s. It never worked consistently even after I modified the circuit to allow a ten-turn variable resistor to help find a more accurate firing point of the lamp. It never worked correctly and consistently from day one. I still have the unit and replaced the entire multiplex decoder with a LM4500 IC based decoder which works like a champ and is easy to adjust and drives an LED indicator now. McIntosh had some early tube type multiplex decoders that drove an incandescent lamp, but had a transistor to turn the lamp on and off. That was a better system than any of the neon lamp types.
Joe