Cobra Service Bulletins
Documentation Project

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Bulletin #
Service Bulletin Description
The local NOAA weather station is not received. 18RV, 23 Plus, 41 Plus
All channels are locked on the same transmit frequency. (R130 burning on 148-series) 148GTLST, 148NWST
Tx squeal on 25-series w/SoundTracker engaged 25 Series Radios
Squealing & muffled sound on HG mikes HGM73, HGM75, HGM77, HGM84, HGM84W
Cobra has switched to a different type of potentiometer for the volume and RF
Gain controls. The old potentiometer is round, the new one is square. The
potentiometer mounts on a small PC board. The new potentiometers will not fit
on the older PC boards.
All 148s with front-mount microphone.
Meter needle sticks after transmit, and there is no receive. Pushing the
Soundtracker button (if equipped) may restore proper operation.
All versions of the 29LTD
We have switched to a different PLL chip (IC1). The older chip is the “2816”,
and the new chip now says “29LTD” on it.
All versions of the 29LTD, including models with weather, Soundtracker, and
Disable Soundtracker 25, 29, and 148 with soundtracker
Warble when transmitting on sideband. This can occur if the power supply
cannot keep up with the power demands of the transmitter.
148 GTL, 148 GTL ST, 148 NW ST
No transmit power on AM. 148 NW ST
Excessive PA feedback 19DXIII
Squealing on transmit. 148GTL, 148NWST
This document provides a list of part numbers for the LED channel display. 18, 19, 21, 25, 29, 148
Intermittent transmit, intermittent receive, intermittent modulation, squealing on
transmit or receive, or other erratic behavior.
All CB models
You can still hear sound from the speaker even when the volume control is turned all the way down. 25 WX NW ST
Squealing on receive when using an external speaker. 25 LTD ST
Replacing the NB8719 PLL chip with an MMB8719. 148
Replacing the Nightwatch power supply module. All Nightwatch CB models
Excessive alternator whine. All 25s with front microphone connector
How to add talkback. 200 GTL DX
Receiver overloads when receiving a strong signal, resulting in distorted audio.
In addition there may be a warble in the modulation when transmitting (which
might be described as a popping sound during transmit).
150GTL, 200GTL
Reduced adjacent channel rejection when the Noise Blanker is on. 200GTL
“Speed-up” the echo effect (add reverb). 150GTL, 200GTL
After adjusting the squelch control, sometimes received signals may sound
choppy due to the squelch repeatedly opening and closing.
150GTL, 200GTL
The HF50-12F(Q35 and Q40) finals are no longer available. 200GTL
The frequency display is not accurate.
Modulation may be low with some noise canceling microphones. 200GTL
When transmitting, there is sometimes a “pop” in the modulation. 150 GTL DX
Motor boat noise in RX audio. 25 NW LTD
Excessive acoustic feedback when transmitting with talkback. 29 LTD SE
Adding talkback CB models 25 and 29 (all versions)
The ANT light is coming on even though the SWR is below 3. CB model 29 (all versions with the ANT light)
How to increase the volume of the talk-back. CB model 29 (all versions with talk-back)
How to adjust the talk-back volume. 200 GTL DX with factory talk-back
How to adjust the BRT / DIM lamp intensity. 29 LTD with factory blue lighting
How to increase the talk-back volume. 150 GTL DX
Audio amplifier versions on the 25/29 25/29 Versions
2SC1969 substitute for the 148GTL 148GTL
No Display on the 29 LX LE 29 LX LE

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Disclaimer: Although the greatest care has been taken while compiling these documents,

we cannot guarantee that the instructions will work on every radio presented.