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That's an interesting problem. Have you checked the voltages and frequencies in the IC3 TA7310p TX mixer? Pin 1 gets its 16-17 mhz reference signal from TR20 (osc) which should be 16.649mhz while on ch 34, and 16.659mhz on ch 35 in RX mode. Notice the 10khz difference in freq, are they changing...

At least it's decent looking on the inside for its age. These were real audio monsters with a Johnson base power mic. I believe there was a mod you had to do inside to open up the audio.

That's a great point, I didn't think of that. On a Cobra 29, L22 is the balance coil for ch1 and ch40, and it comes off of the 1/2 Ref Osc pin 10 of the PLL. ON this 858 PLL it would be pin 8, but it's not used in this radio. I assume that's why it wasn't in the synthesizer alignment section...

It sure surprised me when the tone came through my speaker. I'm not sure what to tell you, but I have 37.880mhz at TP6 and the collector of TR17 is around 2.6v and the pll pin 1 is in lock mode. I guess I will wait awhile before I put the covers on just to be sure.

I'm currently injecting a -114dbm signal and I hear it on channel 1 and 40. Currently on ch 19 the -114 signal is around 11db sinad.

Yes

The 1khz signal came through the speaker shortly after applying the 5 volts as I was adjusting L20 and the frequency was I think around 36mhz or somewhere in there.

I've spent a lot of time on this radio over the last couple of months, and I can't thank you Brandon and Nomad enough. I've learned a lot about the VCO 10 pin sip modual. I have no idea what part was effected by jumping the 5 volts and adjusting L20 and seeing the frequency increase, but it...

With my dc meter on TP5, I can turn the voltage down using L20 to .07V and the frequency reads 31.5xxxxmhz on pin 10 of ic5. Turning the core on L20 to the top of the can, raises the voltage to 4.77v which is the Vcc voltage. At 4.77v the frequency moves up to 32.2xxxxmhz. Now when I jumpered...

TP1 does show 10.240Mhz, and pin 11 of the upd858c shows 1.4xxxxMhz.

This morning I was experimenting with C153 7pf cap. I was out of 10pf caps, so I put two 22pf in series to get 11pf. The frequency did go down some. I tried other higher values up to 47pf and the frequency lowered down around 25 Mhz. So I tried two of the 7pf caps in series to bring it down to...

I agree, I can't imagine working or doing an alignment on a radio without a scope.

Well with C153 the frequency on G1 is 31.2xxx and without the cap its 32.8xxx. I did lose the 3v at TP5 which would be expected.

Oh okay, got it. Alright I was able to adjust and peak the 36.57 mhz signals amplitude on my scope. Thank you so much for the help.

Sorry I see I wasn't very clear. I was referring to L24, but it looks like I had my probe on G1 that is getting around 31 mhz signal from pin 10 on IC5. For some reason pin 10 is about 6 mhz low going to G1, but it was changing a bit when I was adjusting L24. But I see now that it shouldn't, so...

Okay, sams says that the voltages for TR18 PLL Mixer is 0v for G1, 0v for G2, 1.77v for the drain, and source is going to ground. These voltages are all correct in the radio. I did try and adjust L24 but the voltage didn't change on G2. G1 & G2 are basically .017v.

Well after slowly tweaking L20 and L24 i do get some static crashes and popping noise through the speaker. I guess that's an improvement, but still no -67 dbm signal through the antenna jack. The voltage on the PLL lock pin 1 is down from 2.2 volts to 1.5 or so, can't get it any lower. I'm not...

Okay, I did re-solder pin 1 of the VCO after my testing. Thanks for the data sheet on the ECG 1203. The only thing that I'm not sure of is according to the sams schematic, pins 2,6 and 9 are ground, and pin 8 is 4.99v supply. I guess the data sheet for ECG 1203 looks like pins 2,8 and 9 should...

Hello, I have been working on a Zachary T off and on for awhile with a no transmit or receive problem. I'm not a real tech, but I have enjoyed fixing a few cb radios over the last few years. This was listed as a tech special on Ebay, and it has been a bigger challenge than I thought it would be...

Looks like Lou addresses the rumors that have been floating around about him on his QRZ page, maybe he just recently updated it? Also, he mentions his phone keeps ringing and he just doesn't have time to answer all of the calls.