Cobra 2000GTL Super Star UFO 1604 Unlocking issue

[Pick]

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.

 

[Smokinone]

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.

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.

 

[Pick]

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.

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.

 

[Smokinone]

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.

 

[brandon7861]

Check this out. Look at the tech bulletin.

https://cbtricks.org/miscellaneous/vco/redco/digi-scan_ufo/graphics/redco_ufo_tech_aid_0011.pdf

 

[Smokinone]

Is the redco the same as the UFO Super Star 1604?

 

[brandon7861]

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.

 

[brandon7861]

I did find this online

 

[Pick]

I did find this online

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.

 

[brandon7861]

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.

 

[AudioShockwav]

Live View of the problem



And welcome to the forum.

73
Jeff

 

[brandon7861]

First comment. I'm curious what the problem turned out being.

 

[nomadradio]

My first guess would be a dirty mode selector. If it interrupted the 11.325 crystal when turning the knob, could that befuddle the PLL in the UFO?

73