Cobra 2000 Trying to save from a crappy 2030 replacement

RedEye · Post by **RedEye** » Wednesday 3rd Oct 2007, 12:32

I have a 2000 gtl that given to me as a project. It has had a 2030 final swap (very poorly) and only shows about .3~1 watt maxam SSB no visable watts and no visable audio movement. I removed the add on parts, 2030 final, carefully cleaned up the solder puddles... (heh heh) and replaced the 2166 and 1969 final. Still no output and I noticed the 2166 gets real hot fast on a 2~4 second key up. Modulation moves the meters on AM (dosey meter) but still less than 1 watt.

I would love some advise on where to start on this one. I don't want to hunt and peck, and make things worse! Great looking radio, hopefullu I can salvage it!

Thanks in advance,

ramblingman · Post by **ramblingman** » Thursday 4th Oct 2007, 3:05

hi there,,,i guess you know there is alot more involved in this mod than just changing the driver and final..here is the mod,,so just reverse it to remove..remove l-40,so youll need to replace l-40,remove c-149,,so youll need to replace c-149..remove r-181,,so youll need to replace r-181..install jumper wire across r-181..so youll need to remove jumper wire..add 470 pf disc capacitor across c-152..youll need to remove this..add 33 k resistor from gate leg of erf-2030 to r-180..youll need to remove this....p.s..this is just the final only mod..so if both the driver and final was replaced with erf-2030s more will have to be changed......ramblingman

RedEye · Post by **RedEye** » Thursday 4th Oct 2007, 3:06

Thanks rambling man, i did just that, swapped tr37 with a good unit no change, good radio still works, i noticed the voltage at the final drops from 13.8 to around 6v when keyed....

ramblingman · Post by **ramblingman** » Thursday 4th Oct 2007, 16:05

hello once again....have you noticed when you dead key,does the meter light dim??

RedEye · Post by **RedEye** » Friday 5th Oct 2007, 0:20

No, it stays up, The power supply holds voltage.
I put a cobra 29 beside it and when I key the 2000 the 29 picks it up so I belive the driver is working.

The final voltages:
Source - Ground
Drain - 13.8v
Gate - 0.0 v

When Keyed:

Source - Ground
Drain - 6.48v
Gate - 1.7v

I have used both the built in power supply (12.8v) and a remote power supply (13.8v)

Final dosent get warm, but the 2166 gets hot on a 2-3 second key. I have tried new final and driver... I now have a ~.1 dead key and when I modulate, I get about a 2 watt swing.

I'll wait to hear back before trying anything else!
Thanks again for helping!

ramblingman · Post by **ramblingman** » Friday 5th Oct 2007, 4:52

hi there,,,thats to much drain on driver,,must be something dead short before driver stage..id check the pre-driver.

RedEye · Post by **RedEye** » Saturday 6th Oct 2007, 2:05

OK, played with it a little more last night. Lifted center leg of 2166 driver and checked for ground on the pc board. I have a working 2000 beside it and noticed these differences though....

working 2000:
TR24 2.8v - 13.v - 2.8 volts slight change on outer legs when keyed

non-working TR24 6v - 12v - 6v no change or at least not noticeable on key...

when keyed the good unit drops voltage on the d1135 (mounted beside the TR24 on one leg, the non working (which has a C1419 instead) does not drop voltage... (leg torwards the front of the radio)
Swapped TR24 and C1419, same result...

Both are PC-497ab boards...

Thanks again for the advice and help, 'm not a pro at diagnosing, but can follow the good direction from you guys!