Your receiver is often the centre of your system, so when it needs a little TLC and is not up to par, the original complaint is addressed, however we do not just service the obvious and hand it back to you. As a matter of course, everything is gone through. Every function, every switch, control, input, nothing is overlooked, The tuner is FULLY aligned as well, including even the smallest details such as scale indicator mechanical alignment to the 0 index, electrical alignment, and every tuning string pulley being oiled. Even the internal tuning knob shaft is often polished and oiled. When tuned, the frequency you select is exactly the frequency playing.
All required service is performed in accordance with the original manufacturer using ORIGINAL components, NO cheap substitutes or re-stamps are ever used. Every switch and potentiometer, if equipped, is washed with Caig Deoxit, then rinsed a second time.
Alignment includes setting the indicator from bottom of scale to top end of scale to match fully closed and fully open tuning capacitor referenced to log. Entire path of tuning string oiled (pulleys, tuning knob shaft, tuning capacitor shaft, and friction areas of indicator). AM alignment includes peaking of RF and IF stages, trimming the tuning capacitor for equal sensitivity across dial, and confirming that the dial indicator is exactly linear with the tuned station i.e 720kHz on dial is in fact 720kHz. FM section includes all of the same procedures. 98.7mHz is in fact 98.7mHz in addition to multiplex alignment for proper stereo separation and suppression of carrier.
Final confirmation of performance is performed using an RF and MPX generator. Pre-amp section tested for every single function and adjustment. All inputs, including phono confirmed as operating as designed. Phono section is also verified as having correct RIAA equalisation curve.
On solid state receivers like the Pioneer SX-1080 above, amplifier section DC offset, if adjustable, is set to exactly 0mV, and allowed to idle for 45 minutes to confirm stability. If non-adjustable and there is no more that several mV of offset, we will match the differential pair to achieve this. Afterwards, the amplifier section is CORRECTLY biased to eliminate all crossover notch at the transition between device polarities (push half of signal switching to pull half of signal). This is done into a 4 ohm load at 10kHz with one watt of output. This impedance resolves, visually on the oscilloscope, any crossover notch, regardless of the impedance connected in normal use. The frequency of 10kHz is also being used being as harshness from under biased output stages almost always manifests in the 10th octave of human hearing 10kHz-20kHz. It is set to the point where the output is free of crossover notch, and locked in. Just enough forward bias for a clean output, and a cool running output stage. This all applies to direct coupled output stages. In older capacitor coupling output designs, the AC balance of the output stage is set using the permanently used impedance (usually 8 ohms) for symmetrical full power clipping, performed at 400Hz and again at 1kHz, which is extremely important. This allows both halves of the signal to clip at the same point during full power transients. Bias is set in a traditional fashion as outlined above for direct coupled output stages. After confirmation of all functions, designed output power is verified.