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Post by Raccoon on Jun 25, 2020 10:06:45 GMT -5
Hey everyone , I have a Cobra 2000 GTL that was my Grandmother's . It hadn't been turned on in over 15 years until my Mom fired it up one day , and left it on for about a year ... almost constantly . Then when I got it , I hooked it up and started using it and it worked beautiful for a few months ... then all of a sudden , one day it started drifting way off frequency when I'd key up .
I was just wondering if anyone here has any idea what is making it drift off like that ?? I use to have a really good CB repairman in my area , but he isn't doing much anymore , if anything at all ... and due to the fact that it was my Grandmothers ... I don't want to risk it by shipping it in the mail . So I was hoping it was something I could fix myself .
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Jun 25, 2020 14:35:24 GMT -5
Hey everyone , I have a Cobra 2000 GTL that was my Grandmother's . It hadn't been turned on in over 15 years until my Mom fired it up one day , and left it on for about a year ... almost constantly . Then when I got it , I hooked it up and started using it and it worked beautiful for a few months ... then all of a sudden , one day it started drifting way off frequency when I'd key up . I was just wondering if anyone here has any idea what is making it drift off like that ?? I use to have a really good CB repairman in my area , but he isn't doing much anymore , if anything at all ... and due to the fact that it was my Grandmothers ... I don't want to risk it by shipping it in the mail . So I was hoping it was something I could fix myself . There could be several things that cause frequency drift (dirty clarifier pots?). Hard to tell for sure 2nd hand. Also are you sure the radio itself is actually drifting, or is the counter drifting? Also, earlier versions of the Cobra 2000 fall into the date range where 10V electrolytic caps tend to fail more frequently than most. I had a bunch go bad in my 2000. Being that it was left on for such a long time, that could have helped those caps to dry out and fail.
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Post by Raccoon on Jun 25, 2020 15:53:52 GMT -5
It's the radio drifting , not the frequency counter ... because I've been talking on SSB with some friends when it did it .
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Post by 2600 on Jun 28, 2020 23:34:45 GMT -5
I would guess that the lights on the front were dimming on modulation peaks when it did this. If so, this could be caused by a tiny 10uf 50-Volt electrolytic capacitor on the power supply regulator pc board. It's the only one on that board.
Cheapest thing to try first, at least.
73
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Post by bigmotor on Jul 17, 2020 20:36:30 GMT -5
Hello everyone, I'm new to the forum. I need help repairing the receive side of my GTL2000.
I do know that it's only the sound from the speakers that is bad. The radio transmits and receives through the s meter no problem. When you key the mic and talk the s meter reacts as designed, when released you will see the s meter in the receive mode moving across the scale showing that it is receiving a signal. Suggestions please and thanks.
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Post by ytradio on Jul 19, 2020 19:16:17 GMT -5
The very first thing that I would try is tapping into the speaker connections with a known good speaker, or plugging into the external speaker jack.
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Jul 20, 2020 20:06:43 GMT -5
Hello everyone, I'm new to the forum. I need help repairing the receive side of my GTL2000. I do know that it's only the sound from the speakers that is bad. The radio transmits and receives through the s meter no problem. When you key the mic and talk the s meter reacts as designed, when released you will see the s meter in the receive mode moving across the scale showing that it is receiving a signal. Suggestions please and thanks. First question, is the mic wired correctly, or could there be a broken wire in the mic plug? Second question, do you have the external speaker connected, and is the speaker switch in the right position? The Cobra 2000 does not have an internal speaker, so if you don't have the external speaker connected, you won't hear anything. If the transmit modulation is working, then the audio amp is good, so I'm betting the issue is a simple one.
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Post by 2600 on Jul 23, 2020 0:00:58 GMT -5
Inside find C186. It's a 220uf electrolytic cap about a half-inch inboard from the TA7222 audio-power chip, towards the rear end of the chip. If you can remove the solder from one foil pad so the capacitor's lead wire is not touching the rim of the hole, this will take C186 out of the circuit.
If this restores the receiver audio, you'll find that it sounds a bit tinny, and may even squeal when the volume is turned up. A new cap at C186 would cure that.
And if taking one lead of C186 doesn't wake up the receiver audio, the problem lies elsewhere.
But the combination of symptoms strongly suggests looking at this part.
73
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