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Title: SX-42 S meter adjust pot Post by: k5ygc on September 03, 2012, 08:24:33 AM Manual calls for a 500 ohm S type pot? I tried a linear type and it will not adjust to far left zero. Cannot find any info on type "S"
Title: Re: SX-42 S meter adjust pot Post by: WQ9E on September 03, 2012, 09:06:13 AM A linear pot is fine but the original is a 2 watt wire wound so a typical carbon pot is not going to be OK there.
If the pot you have meets the 2 watt spec AND it provides a resistance from near zero to 500 ohms then the problem lies elsewhere, perhaps an out of spec resistor in the meter bridge circuit. On Edit: You really should use a wire wound pot. Carbon pots get noisy when they have DC current flow and a noisy/intermittent pot is not a good thing in a meter circuit. Title: Re: SX-42 S meter adjust pot Post by: k5ygc on September 03, 2012, 06:06:32 PM OK thanks, its a 2 watt so will find a wire wound and check the rest of the circuit thanks
Title: Re: SX-42 S meter adjust pot Post by: ke7trp on September 03, 2012, 07:25:46 PM Also... If you look at the meter face, its adjustable there. So you will have to zero the pot and the mechanical zero. Check voltages before you go further. I struggled with this for a while. In the end, The RF amp tubes even though they checked 100% on my TV7 where the main cause. I think they are 6ag5? I cant remember right now. But swapping them for others would really effect the S meter EVEN after I peaked the RF coils. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
I was never able to get the S meter to work from zero to 40DM. You have to decide on peak being accurate and zero off, Or vice versa. This is after EVERY cap and resistor was replaced. The S meter system in the radio is a bad design. C |