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Dial Calibration Problem on 41-295
#2

What are you using for an output indicator? Your ears are not good enough to trust as an accurate output indicator during an alignment procedure, and I don't care how many "restorers" claim all you need are your ears. They do not know what they are talking about, period, end of story. You should be using an analog output meter (good) or oscilloscope (better). Ideally this output indicator should be connected across the AVC line; if this is not possible, alternate (but less accurate) methods include connecting between plates of the output tubes, between plate and screen of one of the output tubes, or across the speaker voice coil.

Is your signal generator known to be accurate? Many aren't, which is why I now run mine through a frequency counter to obtain the best possible alignment on every radio that crosses my bench.

Now to address your questions...

Adjustment (20A) is for setting the oscillator to 1500 kc on the AM band; (10A) tunes the antenna circuit for best resonance at 1500 kc. You may not hear a lot of difference when adjusting (10A), but again, an output indicator is the only accurate way to tell what effect this adjustment has on the circuit.

Adjust (20A), then (10A), then switch to 580 kc to adjust (20).

Now when you adjust the low frequency padder (20), a different procedure is utilized. This is known as "rocking" the tuning condenser. What you do is tune in your generator signal of 580 kc, which may - or may not - come in at 580 on the dial. Now turn the padder (20) slightly, and move the tuning thumbwheel to follow the signal. If the signal is getting weaker, turn padder (20) in the opposite direction slightly, then follow the signal with the tuning thumbwheel. The goal here is to get the signal as high as possible; when making this adjustment using the "rocking" method as outlined here, you will reach a peak where the signal reaches its strongest point, then will begin to drop off. You want the adjustment to be at the point where the signal is loudest, even if the 580 kc signal is not coming in at 580 on the dial. This adjustment is not meant to make 580 come in exactly at 580 on the dial, but to make the oscillator track with the set's IF circuit.

Once you finish this adjustment, go back to 1500 and readjust (20A), then (10A).

After that, proceed to adjust the SW bands as given in the set's alignment procedure.

This all assumes you performed IF alignment before beginning to do the RF alignment.

--
Ron Ramirez
Ferdinand IN


Messages In This Thread
Dial Calibration Problem on 41-295 - by hyounce - 12-07-2010, 01:54 PM
Re: Dial Calibration Problem on 41-295 - by Ron Ramirez - 12-07-2010, 03:10 PM



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