Help Restoring A 142 GTL with A 2SC2078 Driver Mod

[Robb]

1000 milliamps = 1 amp.

So, if your meter is reading .41mA (that is, point forty-one millamps), that is not even one milliamp. Point forty-one milliamps is just barely under ONE milliamp. 410 microamps to be exact - not milliamps. So then it is waaay too low and needs to be turned up to 25mA. The milliamp range on you meter should be set to mA; not A or uA.

 

[LeapFrog]

1000milliamps=1 amp.
So, if your meter is reading .41mA on the milliamp range on you meter set to mA; then it is waaay too low and needs to be turned up to 25mA.

About to fire it up on the proper range, be back with the numbers soon.

 

[LeapFrog]

40 mA for the driver, 140 mA final,

Way off, time to set it right and see if she runs tip-top!

 

[LeapFrog]

40 mA for the driver, 140 mA final,

Way off, time to set it right and see if she runs tip-top!

Got the driver down to 35-36 and it will not go lower, the Cobra 142 GTL Sam's info I found in another thread says 35 mA for driver and 45 mA for the final, I'm going to try this at first if i have bad results i'll try to adjust them some more.

 

[LeapFrog]

40 mA for the driver, 140 mA final,

Way off, time to set it right and see if she runs tip-top!

http://www.cbtricks.com/radios/teaberry/stalker_ix/graphics/teaberry_stalker_ix_xv_sm_pg01_20.pdf

Same pc-385, different set of bias#'s lol!

 

[LeapFrog]

http://www.cbtricks.com/radios/teaberry/stalker_ix/graphics/teaberry_stalker_ix_xv_sm_pg01_20.pdf

Same pc-385, different set of bias#'s lol!

Arggh still has the backswing even with a 2watt carrier, time to change electrolytic caps!
Now ssb output is down to 3 watts avg from 10-12 avg... Probably much cleaner though who knows.

 

[Robb]

Just get the bias settings correct by the book. At least - for a start - you will at know that those settings are solid. The problem may well be elsewhere, such as the state of tune of the TX coils. They may need to get peaked next.

Tuning a radio also tells us if each section is running up to specs at these test points. This is useful. Radios that don't work can be found by testing test points. Being way out of specs and/or not having a signal at all is a bet that you may have found problems within that particular circuit. Or; one is not properly set up the test gear. Has to be one or the other.

 

[LeapFrog]

Just get the bias settings correct by the book. At least - for a start - you will at least know that those settings are solid. The problem may well be elsewhere, such as the state of tune of the TX coils. They may need to get peaked.

Tuning a radio also tells us if each section is running up to specs at these test point. Radios that don't worl can be found by testing test points/ Not always; but often enough to be true a lot of the tme

Thank You Robb.

 

[LeapFrog]

Just get the bias settings correct by the book. At least - for a start - you will at least know that those settings are solid. The problem may well be elsewhere, such as the state of tune of the TX coils. They may need to get peaked.

Tuning a radio also tells us if each section is running up to specs at these test points. This is useful. Radios that don't work can be found by testing test points. Being way out of specs and/or not having a signal at all is a bet that you may have found problems within that particular circuit. Or; one is not properly set up the test gear. Has to be one or the other.

The driver would only go as low as 35mA, with the potentiometer cranked, also AM carrier will not reach 4 watts while turning the vr6 (all the way) I got 3.75 watt max dk.

Starting to think some other tom-foolery happened inside this rig.
-LeapFrog

 

[Robb]

Tested in USB mode?

 

[Robb]

The driver would only go as low as 35mA, with the potentiometer cranked, also AM carrier will not reach 4 watts while turning the vr6 (all the way) I got 3.75 watt max dk.

Starting to think some other tom-foolery happened inside this rig.
-LeapFrog

Fair bet; what is your next move?

Did you put the biasing diode back into the driver circuit?

 

[LeapFrog]

Fair bet; what is your next move?

Did you put the biasing diode back into the driver circuit?

Fair enough, the MV1Y bolted to the heatsink I take it, was present in the circuit with the 2078 and still is! In between vr8 & r152 I see silkscreening for a diode but no part # and no diode present.

Was going to tune the "cans" for rf output, and correct the reverse swing hopefully but now my only 5 pin mic has a broken wire @ the plug and im trying to repair that lol!

 

[LeapFrog]

Update: mic is re-wired an working.
While playing about with the rig "testing it out", i noticed my carrier dropped to 2 watts from 3, I measure 13.8v @ the psu & inside the radio i have 12.02v. Must be a bad cap somewhere or dirty cb/pa switch because yesterday I noted the radio having supply voltage inside, now that's no longer true...

 

[222DBFL]

Man sounds like someone took the screwdriver to this one LeapFrog. Someone that didn't know shizz about radios! Sounds about like the tech here in my area. Says he is an authorized kenwood repair station and dude can't fix a CB radio LOL!! I am still scratching my head about that one. At any rate, keep at it man. If you get frustrated, step back and let it be for a while and come back to it! You'll get it i am sure. With the help you have it will get resolved. Here is yo hoping you get it fixed and working correctly.

 

[LeapFrog]

Man sounds like someone took the screwdriver to this one LeapFrog. Someone that didn't know shizz about radios! Sounds about like the tech here in my area. Says he is an authorized kenwood repair station and dude can't fix a CB radio LOL!! I am still scratching my head about that one. At any rate, keep at it man. If you get frustrated, step back and let it be for a while and come back to it! You'll get it i am sure. With the help you have it will get resolved. Here is yo hoping you get it fixed and working correctly.

Hi ya 222, yes this was a craigslist special, I should've ask to take the lid off before the purchase, I was really happy to be getting a ssb Cobra & the buying experience was more emotional than logical lmao (20/20 hindsight)!

It's about average on the "golden-screw-drivered" radio scale.
Unknown amounts of clipped/zapped/spread/removed parts "strategically hidden" throughout the board, buried almost so that if you didn't know where they modded, you might not see it, like anyone gets pointers on "past mods done" while buying a used cb. Haha if only we got a complete of list of what was ever done along with every radio purchased lmao, if only!!
I guess half the fun is making it oem, or better and half of that fun is all the hell involved in finding everything, I looked for cleaner(maybe newer) solder joints, shinier parts & the like. I will keep at it!

God Bless
LeapFrog is over & out, 73.