Recent content by Tolteca

Okay so far the only weird thing I've found is that I cannot adjust the modulation limiter. I found a clipped diode and one covered with sony bond, I've replaced both of these diodes as well as the 10k adjustment pot with no solution. I'm not using a power mic or anything like that, the wave...

OKay will be taking a look.

Found the issue, the problem was a resistor leaning onto TR47. Poked around a bit and it was fixed just like that. Thanks a lot for the help, did not know there was a muting function built into these radios. The other issue now is what I call backward modulation. I aligned the radio and I...

Hey guys, This is the same 148 I was dealing with in the other thread but I decided to focus that thread specifically on the frequency mod. I've had this 148 for a while now and despite having aligned it and it being an overall good performer the one issue I never took care of was the low...

I'll report back when I have the other 148 on the bench. Stay tuned.

I did use a variable resistor in combination with a fixed resistor to get the best selectivity within the 4.4 to 4.7 volt range which is where the transition takes place. Above or below that gives me either low or normal frequencies. Can't seem to dial it in and make it do the thing so the bug...

I tried doing it with a variable resistor from pin 10 to ground with no results. At around 4.5v the chip just switches from low frequencies to normal frequencies with a bit of a grey zone in between where the chip can't decide what to do. I tried really fine tuning it in but I can't seem to...

Huh. I'd read a Brazilian made MB8719 datasheet that talked about this mid state but I'd never seen it actually used before. I did think this had something to do with this mod since I was always reading about 4V on pin 10 when this mod was activated. I just thought it was so weird where they...

So I just realized that this is pretty much the same as the pin 17 mod except that you are DC isolated from PIN17 through C87. This is the 34Mhz trippler signal that you're feeding into pin 10. So apparently what is probably happening is that you are making the gate switch so quickly between...

Hello all, Back at it again. There seems to be little talk about this modification. This is a strange mod in which you place a variable resistor from L21 to PIN 10 of the MB8719 to achieve a 128 upward channel shift which is amazing compared to the usual 64 upward shift you get from simply...

Hi guys, Sorry for not updating you sooner. I managed to fix and sell the radio. It did quite well once everything was fixed up. Here is a picture of how I managed to resurface the transistors. First off we have how they started off. You can see the bow in the transistor. Then we have...

Hmm. The issue is the base of the transistors. They tightened the screws down with the tabs soldered in and without enlarging the holes. What this did is bend the screw tabs down and bend the metal part of the transistor into a slight U shape. I think it might be best to sand the surface of...

Turns out the issue was the ALC adjustment. Once I wiggled around with one of those pots the modulation came back on AM too. Wouldn't have thought they were so related. Modulation is working great. Since I had to wiggle back and forth a bit with the pots and since they wear out very quickly...

I've gotten through most of the alignment now. Most of it has gone just fine. I had cut the top off the shielding over the VCO circuit. I couldn't access the test points. Came out nice. I would have had to use my heat station to desolder this off which I figured was a high risk. I was...

Yeah I don't think I'm gonna end up keeping this. If you guys were to sell a Cobra 200, how much would you guys ask for it?