Alright guys thanks for the additional info. I might be aquiring a junk 148 soon that might have an MB8719. If I get it I will try modding the RCI chip and will report back on whether or not it worked. I'd just hate to blow the thing up and be stuck without a replacement. It's running on 8V by the way
I found two crystals out of another radio that was modded for lower frequencies and I've done the mod on this radio now. Just got done doing the alignment and all is working well. Had a bit of a hard time with my SSB alignment, turns out that my frequency counter was making the 7.8Mhz oscillator shift down a bit. Putting a 33pf cap in seris with the test point solved this issue.
By the way, my service manual says to use TP14 which is not in this version of the radio, perhaps only the night watch version. I couldn't find a place to get a stable reading for the 7.8Mhz oscillator alignment until I hunted a bit. The best test point I found was the junction between C98 and C123. In fact this junction leads to a small hole right infront of the crystal which looks like a test point that was left out and is unmarked. On all the test points I added a small lead for future alignments. With this and putting my ground lead on a near by ground connection I could finally read the 7.8Mhz frequency for the SSB offsets. Problem here is I still couldn't get a stable reading anywhere for the 7.8Mhz AM carrier,and yes you have to put it in TX for the AM adjustment which I did. Only way I was able to adjust this was to transmit and adjust this coil til the AM TX was on frequency. This of course after having aligned the 34Mhz oscillators. I did this and went back and forth between the 7.8Mhz USB and LSB adjustments and the 7.8Mhz AM adjustment a few times til everything was dandy. For SSB I still adjusted as the manual states.
Only cocnern I have right now is that the clarifier makes the VCO go out of lock when it's fully clockwise. Is that to be expected? Could that damage the VCO?
I found two crystals out of another radio that was modded for lower frequencies and I've done the mod on this radio now. Just got done doing the alignment and all is working well. Had a bit of a hard time with my SSB alignment, turns out that my frequency counter was making the 7.8Mhz oscillator shift down a bit. Putting a 33pf cap in seris with the test point solved this issue.
By the way, my service manual says to use TP14 which is not in this version of the radio, perhaps only the night watch version. I couldn't find a place to get a stable reading for the 7.8Mhz oscillator alignment until I hunted a bit. The best test point I found was the junction between C98 and C123. In fact this junction leads to a small hole right infront of the crystal which looks like a test point that was left out and is unmarked. On all the test points I added a small lead for future alignments. With this and putting my ground lead on a near by ground connection I could finally read the 7.8Mhz frequency for the SSB offsets. Problem here is I still couldn't get a stable reading anywhere for the 7.8Mhz AM carrier,and yes you have to put it in TX for the AM adjustment which I did. Only way I was able to adjust this was to transmit and adjust this coil til the AM TX was on frequency. This of course after having aligned the 34Mhz oscillators. I did this and went back and forth between the 7.8Mhz USB and LSB adjustments and the 7.8Mhz AM adjustment a few times til everything was dandy. For SSB I still adjusted as the manual states.
Only cocnern I have right now is that the clarifier makes the VCO go out of lock when it's fully clockwise. Is that to be expected? Could that damage the VCO?
