Onkyo TX-37 functions

[Ylli]

I acquired an Onkyo TX-37 receiver in fairly good shape. Speaker switch was intermittant (fixed with DeOxit) and the unit would not go into stereo mode (went into mute instead). Got that fixed too.

Now there are a couple modes I don't quite understand. Your can set it for 'FM Tune Level' High/Low. Is that the sensitivity of the auto scanning? Also, it has front panel lights for 'RF Mode' Local/DX. Would appear to be an RF sensitivity selection, but I don't see any way of changing it. Is it more of a signal level detector indicating a strong or weak signal?

 

[sgrossklass]

I think you're correct on both counts. The AGC circuit seems to be doing its own thing, you just get an indication of when signal strength has exceeded a certain level. Strong-signal handling should be well above average for what it is.

If you feel like doing some mods, it would not surprise me if the US model had some unpopulated spots for the second IF amp and third ceramic IF filter present in the 220V version (jumped over, of course). Not sure what a good IF amp transistor would be if you can't find the original 2SC1923, but it looks like the US version uses two 280 kHz filters, and the European version has three 230 kHz GDT jobs (SFE10.7MM). If you have some DX ambitions, I would move the existing 280 kHz filter to the X103 spot and install a 180 kHz MS3 in the X101 spot; otherwise even 3x 280 kHz would be an improvement. Now whether mixing new and thoroughly pre-aged filters is a good idea is another question entirely; ceramic filters have a habit of drifting.

 

[Ylli]

The unused holes are there. But this receiver seems to have good sensitivity and selectivity - don't think I would gain much by adding another IF stage. Also see significant differences in the RF/converter section between the US and Euro versions. The Euro version lists an image rejection of 80 dB, and the US version only 40 dB.

 

[sgrossklass]

The unused holes are there. But this receiver seems to have good sensitivity and selectivity - don't think I would gain much by adding another IF stage.

I guess selectivity wouldn't be much to write home about over here. 2x 280 kHz is not exactly being considered "DX-worthy".... but I guess it'll do an alright job if 200 kHz separation is all you need and the AGC does its best to keep the IF stages in the linear operating range.

Also see significant differences in the RF/converter section between the US and Euro versions. The Euro version lists an image rejection of 80 dB, and the US version only 40 dB.

That's pretty typical - 4 gang frontend for Europe with its crowded FM band, 3 gang for the US. Not sure why the difference in frontend selectivity between 3 and 2 tracking circuits would be this disproportionate. In any case this makes finding a decent tuner to be "souped up" with some mods for DXing much easier over here.