23-09-2022, 04:21 PM
OK, so the output pair seemed to be a little keen. I swapped two 3K0 biasing resistors for 3K9 and this reduced the quiescent current overall to 6.6 mA without causing any noticeable distortion and while keeping the centre point between the pair at 4.5V with a 9V supply.
A point of note is that this little pocket set exhibited a lot of crackling at one end of the tuning range. Indeed it was totally silent when inverted at certain tuning positions. The tuning dial was far too easy to rotate, too. I was able to remove the polyvaricon, separate it from its cover, and tighten the four tiny nuts holding it together. This stiffened up the dial and cured the crackling. The IF was nearly 20kHz off, so I realigned it, along with the RF alignment. It now performs quite reasonably, if not spectacularly. What is slightly odd is that the specified MW frequency range is 547-1600 kHz, which is OK, but LW is 150-240 kHz. The high frequency end of LW is well short of the allocated 283.5 kHz. I can just get RTE Radio 1, but not well. I wonder why they did this.
A point of note is that this little pocket set exhibited a lot of crackling at one end of the tuning range. Indeed it was totally silent when inverted at certain tuning positions. The tuning dial was far too easy to rotate, too. I was able to remove the polyvaricon, separate it from its cover, and tighten the four tiny nuts holding it together. This stiffened up the dial and cured the crackling. The IF was nearly 20kHz off, so I realigned it, along with the RF alignment. It now performs quite reasonably, if not spectacularly. What is slightly odd is that the specified MW frequency range is 547-1600 kHz, which is OK, but LW is 150-240 kHz. The high frequency end of LW is well short of the allocated 283.5 kHz. I can just get RTE Radio 1, but not well. I wonder why they did this.
My name is Steve, but I answer to most things like "Oi, you!".
