cobra 148 unlock PLL

[Robalo]

update now I have 3 radios with the same problem same voltage at tp9 one is like factory never touch anything mmm is taiwan made

 

[AZradiotech]

Most likely bad caps on all 3, common problem, with these old radios, causes all kinds of problems.To find this you'll have to know rf and electronics theory and trouble shooting.

 

[Robalo]

i just got another radio with similar problem and i still working on this one

 

[Robalo]

 

[nomadradio]

More than once I have seen a RCI-made radio that had the three trimmer coils each set one channel low. The tuning range of the coils used to set clarifier center is a lot more than needed.

The 148 could do the same thing.

Maybe.

73

 

[brandon7861]

More than once I have seen a RCI-made radio that had the three trimmer coils each set one channel low. The tuning range of the coils used to set clarifier center is a lot more than needed.

The 148 could do the same thing.

Maybe.

73

That makes sense right there. Pull each of the 11MHz cans by 3.333kHz and the tripler moves the VCO 10kHz and now you have 6 private channels to talk to your buddies on.

 

[brandon7861]

The counter in that last video is showing 34.918MHz on ch1. That don't correspond to where the VCO needs to be for ch1, or one ch lower ftm (26.955MHz), it is supposed to be 34.765 on ch1, and if it were intentionally shifted down a channel, then 34.755. With the FC-357 counter reading 26.955 there, that bench counter reading don't make sense.

My thought, if both videos are of the same radio, is that Nomad is right, and that the radio was intentionally shifted down 1 channel, but I suspect that after you removed the FC-357 counter and started using the bench counter, you may have accidentally tried adjusting the VCO for ch19 (34.985) instead of ch1, and in the process of doing so, it suddenly lost the ability to track your changes and fell completely out of lock and is now running at its lower limit and can't go low enough to re-establish that lock.

I believe you need to first adjust the slug to get the VCO back to 34.755, then adjust the tripler oscillator to bring that back up to 34.765 where it belongs (on AM anyhow, but all three slugs will need adjusting), and then reverify the VCO tuning range on all channels.