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Cobra 2000GTL Super Star UFO 1604 Unlocking issue

Pick

Pick

New Member
Jan 27, 2026
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I just installed a UFO (1604) on a working 2000GTL, all modes and functions worked well. After following Super Stars installation instructions (and some help from DIGISCAN DS-400 Manual) the following happens.
Sometimes the UFO turns on and locks with the radio, at times you have to turn the radio on/off a few times to get the UFO to lock.
When I do get it to lock, max frequency is 27.670 then unlocks. It unlocks down around 26.5.
When working and I change modes AM/USB/LSB it unlocks and I have to restart the radio, UFO works until I again change modes. Hmmmm

I tried a loop filter at TP 9, 2200mfd cap from PC ground to physical ground (as per DS-400 instructions) and even powered up the UFO from external 13.8v. power source. Same thing, unlocks when I change modes. I can live with the limited frequency range if I have to but the unlock issue is a no go.

The UFO looks like it has never been installed as the wires/coax still had factory tin job on the leads. The UFO has a couple of the dreaded 10v caps. Think I may swap them out?

Again.... the radio worked very well until I installed the UFO. Radio was recapped and aligned a few years back and RAN like a clock.
 

Pick said:
I just installed a UFO (1604) on a working 2000GTL, all modes and functions worked well. After following Super Stars installation instructions (and some help from DIGISCAN DS-400 Manual) the following happens.
Sometimes the UFO turns on and locks with the radio, at times you have to turn the radio on/off a few times to get the UFO to lock.
When I do get it to lock, max frequency is 27.670 then unlocks. It unlocks down around 26.5.
When working and I change modes AM/USB/LSB it unlocks and I have to restart the radio, UFO works until I again change modes. Hmmmm

I tried a loop filter at TP 9, 2200mfd cap from PC ground to physical ground (as per DS-400 instructions) and even powered up the UFO from external 13.8v. power source. Same thing, unlocks when I change modes. I can live with the limited frequency range if I have to but the unlock issue is a no go.

The UFO looks like it has never been installed as the wires/coax still had factory tin job on the leads. The UFO has a couple of the dreaded 10v caps. Think I may swap them out?

Again.... the radio worked very well until I installed the UFO. Radio was recapped and aligned a few years back and RAN like a clock.
Click to expand...
I can tell you this seems to be normal. I have the same setup I inherited from my father in law and I know he played with it for a long time, and many hours of adding capacitors etc. Still has the same issue. I played around a little myself, but I am not a tech. Basically I moved what he had, then moved it back. I also found that you can move from AM to SSB, back and forth and it will lock as well...at least it did for me.
I thought it might be the 8V from the module not being consistent for the lockup, but never got beyond that. I know I played with the voltage in the module and sometimes it would bring it back to lock, and I found it not to be consistent as the power on and off.
 
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Smokinone said:
I can tell you this seems to be normal. I have the same setup I inherited from my father in law and I know he played with it for a long time, and many hours of adding capacitors etc. Still has the same issue. I played around a little myself, but I am not a tech. Basically I moved what he had, then moved it back. I also found that you can move from AM to SSB, back and forth and it will lock as well...at least it did for me.
I thought it might be the 8V from the module not being consistent for the lockup, but never got beyond that. I know I played with the voltage in the module and sometimes it would bring it back to lock, and I found it not to be consistent as the power on and off.
Click to expand...
Last night I tried to hook the UFO to my Robyn 510 (UPD858) radio, this is a very easy installation. The UFO has locking issues on that rig as well. My DS400 works 100% on that rig. I may try the DS400 on the 2000 and see what happens. My good friend had the DS400 on his 2000 and never had one complaint. I will post my results.
 
My father in law was a tech, had 2nd class radio license, Army training as well, and a lot of other training he took. Worked on anything electronic from the tube days and on. I really didn't think I could do anything as I know diddly compared to him. I thought about getting it back to stock, or putting something else in, but it works as it is, other than to lock/unlock now and then, but it's more of a reminder of him so I leave it alone other than getting it on the air now and then. I usually leave it on 24/7 when I have it in line and don't have too much issue with it.
 
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According to posts on another forum, it is not the same. However, I bet given the similarities, the common symptoms may have a common cause.
 
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brandon7861 said:
I did find this online
Click to expand...
Thanks for the tech bulletin, however that is for the REDCO. The Super Star is close but no cigar. I have been hearing from elsewhere that the UFO (1604) is not a great device for the 8734 radios ie Cobra 2000GTL/Madison.... I have all of the cbtricks manuals and various paper work for REDCO, DIGILOG and the Super Star UFO. I have been working between all this info and still TU. I saw NOMAD mentioning the 40+ yr old caps and I do see a few of the DEATH CAPS (10 volters) and might swap them out but that IMHO is a 50/50 chance at best. From what I hear these UFOs are a POS. After I take a days breat I may forge on.
 
Can you scope the collector of the input amplifier and see if the levels it sends to the PLL are sufficient to reliably count? Check all modes.
1769556635051.png
 

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