Hello guys by any chance does someone have a Cobra 142 gtl Alignment procedure info?I have all the equipment such as a scope ect...
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Cobra 142 gtl Alignment
- Thread starter kaos513
- Start date
Just got my first 142GTL, someone "modded" it (hacked it all up) and measuring at the power at the meter lights and ground I got over 15 volts (I assume someone cranked up the output for more power)
I see the adjustment pot, I can adjust it back down for longevity sake. Where should I probe to make sure the board is getting between 12.5-13.8v because I am having my doubts this is proper place to measure (at the meter lights).
Thank you, also
Is vr6 (am power) directly next to the 1000uf cap?
& about this:
Freq. Counter to tp3 (r101) TP3 is gone? Ripped out?
I cannot find an R101 to save my life!
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Thank You SpaceCowboy, is that tr41, or tr40? Or is a tr401 really on the board, I can't see it! tr23 is the largest numbered one i see i have the unit in front of me now.,
This last part is off topic but perhaps someone can elaborate for the sake of knowledge:
bi-polar transistor npn type base, collector, emmiter
Typically can one assume to find the collector on the groundplane,
emmiter to "output"
BASE to "high" for "switching" (apply voltage)
Or is one a current source, one output, and one to "switch"?
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TR401 is the 2SD188 NPN in the schematic, thank you SpaceCowboy.|
From the tr401 emmiter i measure 14.6 volts grabbing groung from a jumper on the main board.
If i measure from the + of the meter led, I get 12.6v using the same ground.
Should I pull the bottom cover off and take my measurment using the neg leg of c804 (the big cap 3300uf).
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Its in there behind the VFO chip. Flat against the board IIRC. Took me awhile to find it too. You'll get it . . .
EDIT:
VCO Chip
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OK got the power supply set @ 13.86 v I can live with that.
VCO i was under the impression this radio used an lc tank oscillator, with caps, resistors, and a transistor pair, obviously i have much to learn, im gonna stare at the board somemore, I need to hook in this 2 wire freq. counter. it will only show when transmitting thats fine, just need a safe pick up point, would the so-239 connector be feesable with a dc blocking cap (I would us a ceramic/mica)
VCO i was under the impression this radio used an lc tank oscillator, with caps, resistors, and a transistor pair, obviously i have much to learn, im gonna stare at the board somemore, I need to hook in this 2 wire freq. counter. it will only show when transmitting thats fine, just need a safe pick up point, would the so-239 connector be feesable with a dc blocking cap (I would us a ceramic/mica)
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NO; you don't want to do that.
Use/make a pickup coil. Just wrap 5 coils of scrap wire around your output coax an tape it in place. Hook up the freq counter to the ends of those leads. Done.
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Thank You Robb, so this method will work no problem with 95% shielded coaxial line?
The ground would be directly connected to the coax outter connector? I Have some magnet wire I can wrap 5 turns, tight like a tvi filter or like a spring?
When my scope comes in I will align this baby, for now I want to make sure it's on frequency, using this guide http://lesterscustoms.com/counter_to_uniden_single_conversion
With a different counter (8 digit fleabay special 2-wire hook up minus power)
I attached my counter to the point circled in the second picture, the frequency was not 10.240 Mhz (but jumping below and above) and was jumping without putting radio into tx.
I care to know i am on frequency so right now im wrapping a pick up coil.
The ground would be directly connected to the coax outter connector? I Have some magnet wire I can wrap 5 turns, tight like a tvi filter or like a spring?
When my scope comes in I will align this baby, for now I want to make sure it's on frequency, using this guide http://lesterscustoms.com/counter_to_uniden_single_conversion
With a different counter (8 digit fleabay special 2-wire hook up minus power)
I attached my counter to the point circled in the second picture, the frequency was not 10.240 Mhz (but jumping below and above) and was jumping without putting radio into tx.
I care to know i am on frequency so right now im wrapping a pick up coil.
