Toza Looks at Three Similar Sony Radios

Thanks, Toza:

I have a Sony ICF-SW100, ICF-SW1000T and ICF-SW7600GR. All of these are (more or less) the same radio in different packages. Sony does great job on SW starting from 41m, has the excellent sync-detector, but... The input for SW design is the aperiodic amplifier (common drain FET). This one has the crazy LC "filter" across the input and standard 470k gate resistor. LC filter resonates on first IF (about 55MHz) and on SW it is parallel (antenna loading) impedance of only 2kOhms. I have removed it (it is useless). Then I had to replace 470k gate for 1M, and serial capacitor from 220pF to 10nF. The radio got the sensitivity of a standard car receiver on high impedance antenna input, from LW up to 30MHz. Then, instead of (noisy) 2SK238 FET on MW loop and FM tuner I have applied Sanyo MOSFET 2SK3737 (pin to pin replacement), have made one bridge on PCB in front of FM tuner to cut noisy loop "antenna" there, replaced tuner bias resistors from Rd=47 Ohms to 100 Ohms (and they did the same on ICF-Pro80) and Rs=33 Ohms to 560 Ohms and everything came more-or-less "normal". MW DX vastly improved. All of these changes don't require LC alignment. There is also one 10nF blocking capacitor on the 1st RF coil to be "turned" to the opposite side to avoid loops.

Then, from the ICF-SW77 they decided to go "cheaper" and save the mixing transistor stage, so they started using the mixer inside of IC CXA1376 which actually created problems (high impedance input on IC relative far away from RF amplifier).

This way Sony has became more usable, still sensitive for stray fields and noise such as PC etc. I had lot of problems with intermodulation because I live on the 12th floor in the city.

 

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Comments

[Angelo]

http://www.ebay.com/itm/Vintage-SONY-MATRIX-SOUNDS-SYSTEM-AM-FM-Radio-Stereo-/131019200274?pt=US_Portable_Stereos_Boomboxes&hash=item1e815a5712

Me like.

[Toza]

If somebody happens to be interested in these mods, I can post position numbers (like C17, R23 etc.) which are to be replaced/repositioned/removed.
Regards, Toza.

[Huesby]

Toza

You seems to know a little bit about electronics and then some... Is there any electronic forum where you actively participate ? If so which one it is ?
Huesby

[Dan]

Is Toza still around on this site, and if so, can he provide an email address for contacts about SONY modifications?

Thanks

[Ed S.]

Doubt it...all the watch talk drove us radio guys away.