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Post by husker on Feb 17, 2018 2:40:03 GMT -5
No, it does this even without a mic connected. I tried my known good D104 and the same issue
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Post by husker on Feb 17, 2018 1:57:41 GMT -5
As I continue to get this project working and it really helps I have my stock 2000 next to it for a stare and compare to see what was removd or destroyed. So I have it working, not real well yet, but as hacked as it was...at this point I am happy.
The one thing I am confused by is the S-Meter pegs to the right as soon as I power the radio up. When I transmit, it drops down to show about 4ish watts, then as soon as I un-key the mike back to being pegged. Any one have any ideas?
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Post by husker on Feb 16, 2018 0:20:57 GMT -5
Folks, Seems when this Cobra 2000 was in the hands of the "golden screwdriver" tech, he removed D52. D52 is a KB262 varistor. I am looking for a sub for this please if anyone knows of one. This radio is ready to go sans this one small piece.
thanks
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Post by husker on Feb 14, 2018 2:10:40 GMT -5
So I have this wire left...I assume it was/is a ground. Am I correct? I intend to just remove it?
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Post by husker on Feb 10, 2018 22:38:09 GMT -5
Apparently, this mod takes the crystal from the main board and cuts the trace where that crystal would normally go. Any one ever heard of this mod? Looks like they removed the 11.325 crystal and put it on a remote switch in order to switch between several crystals for extra channels (a very common way of doing this). But if they didn't first swap out the MB8734 PLL with an MB8719 chip, they're making it tougher than it has to be. I would just remove the whole thing and solder the crystal back in its original place and restore the proper components. I agree, but I worry there many, be more things removed? And yes this does have the 8734 chip
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Post by husker on Feb 10, 2018 17:58:21 GMT -5
Apparently, this mod takes the crystal from the main board and cuts the trace where that crystal would normally go. Any one ever heard of this mod?
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Post by husker on Feb 10, 2018 12:25:40 GMT -5
Help! How do I reverse this crazy main board destruction? THe channel expansion selector switch wires have two of the three disconnected(crap soldering job it appears) and either I try to figure out how to reconnect them or just reverse ths mod. This radio has the MB8734 PLL.
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Post by husker on Feb 9, 2018 19:54:56 GMT -5
The "10V Blues" is when a handful of 10V electrolytic capacitors can, and usually do, short out causing problems. Usually found in audio stages, but can be found elsewhere. Evidently, back in the mid-late 80's, Uniden purchased these caps from one of their vendors, and they must have had a bad electrolyte mix, which caused these caps to fail prematurely. It only seems to affect 10V caps. Other voltage caps don't seem to have the same issues. I've seen these 10V caps fail in dozens of Uniden-based radios both domestic CB's and "export" types as well. But older pre-1980 Uniden radios (like the 858 PLL chassis) don't seem to have the problem. My Cobra 2000 had 2 of them fail. I kind of thought that was what you meant. I am doing all new caps just to be safe
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Post by husker on Feb 9, 2018 14:41:17 GMT -5
lol, yes...after all it is an addiction I blew it out first then used denatured alcohol to clean all the grease looking stuff off the board.It was some what nasty Waiting on a new front plate, the one the seller sent had the toggle switch mounts destroyed. He found me a new one and is sending that. The only thing I don't like about this radio is the "channel mod" has been done to it. I wish I could remove it and put the radio back to stock, but traces have been cut etc. I prefer stock Mine was "all done up", with all sorts of mods. The tone control was repurposed as a power adjustment, there are two holes drilled in the front panel for channel switches, someone installed a roger beep board, and there was a rat's nest of wires connecting it all. I removed all of that stuff and put everything back to stock, except I set the clarifier at +/- 5Khz for the coarse, and +/- 1Khz for the fine. Hopefully this radio works when you're all done cleaning it. They're notorious for the "10V blues". What is the 10v blues?
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Post by husker on Feb 9, 2018 9:08:38 GMT -5
ANOTHER 2000? Wow, this looks dangerously like the beginning of a collection.... I would echo 2600's comments WRT water although I still have my original 1971 vintage Midland 13-885, which was the unlikely victim of a flood back in the 80's. Caked with muddy water inside, I had little choice but to spray the gunk out with pressure water and then dry out with a hair dryer. 30 years later and it's still working. Alcohol is a good solvent. Another is a chemical called "DeOxit". It dissolves crud. I would first blow the entire chassis out with compressed air. That will get rid of the loose particulate matter. Then, whatever tarnish and gunk is left over, you can remove with a solvent, preferably one that dries quickly and leaves no residue. If any residue is left (Stay away from "tuner cleaners" that have lubricant in them) it could affect the tuning of some of the circuits, especially variable caps. lol, yes...after all it is an addiction I blew it out first then used denatured alcohol to clean all the grease looking stuff off the board.It was some what nasty Waiting on a new front plate, the one the seller sent had the toggle switch mounts destroyed. He found me a new one and is sending that. The only thing I don't like about this radio is the "channel mod" has been done to it. I wish I could remove it and put the radio back to stock, but traces have been cut etc. I prefer stock
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Post by husker on Feb 9, 2018 1:02:40 GMT -5
And it begins
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Post by husker on Feb 9, 2018 0:49:16 GMT -5
Water is a bad idea. The small metal cans with the tuning slug in the middle contain copper wire fine as frog hair. Doesn't take much moisture to corrode those wires. Shuts down that part of the radio when this happens. The tiny spaces inside those cans will soak up any moisture and make it tough to dry back out before the damage is done. Denatured alcohol and a brush will not harm plastic materials. Harsher solvents can soften plastic components. In a pinch, 91 percent (or higher) isopropyl alcohol should be okay. Compressed air and a blow gun will speed up drying it out, and help to dislodge loosened gunk that a brush doesn't reach easily. 73 Perfect! Thank you sir!
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Post by husker on Feb 8, 2018 23:46:25 GMT -5
I picked up a Cobra2000, the inside is pretty nasty. Looks like 20+ yrs of dust bunnies, hair/skin and cooking oils. What is the best way to clean this? I would use water and a mild soap, but that can't be good for some of the parts can it? I am looking for any pointers, I like a nice clean radio
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Post by husker on Jan 24, 2018 16:15:11 GMT -5
So I finally gave up and sent the radio to Greg Barkett in hopes of getting this thing fixed once and for all. It ran three days without a hitch in his shop. So that means the issue is somewhere on my end? I tested my antenna system by connecting to other radios, they have no issues, I tried two different mikes (knowing how the 2000 could ground the receive circuit on a bad mike or wire/connection, I figured trying a second mike to make sure the one I had wasn't bad) and I still had the issue. So Greg is doing an alignment now and boxing the radio up. Like he said, if he can't get it to fail, he can't fix it. Yea, I certainly get that lol.....sigh
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Post by husker on Jan 17, 2018 9:11:15 GMT -5
What does pin 9 read? Most of the time if this chip is bad, pin 9 will read wrong. Should be very close to one-half the supply voltage feeding into pin 1. 73 I think at this point I have gone as far as I can go with my limited skill set. I either need to send it to someone to fix or dispose of it by selling the parts. Does anyone know a good tech I can send it to? I know 2600 doesn't do "mail in work" so I am looking for any recommendations please for a good tech. Thanks guys for all your help!
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Post by husker on Jan 16, 2018 16:08:22 GMT -5
What does pin 9 read? Most of the time if this chip is bad, pin 9 will read wrong. Should be very close to one-half the supply voltage feeding into pin 1. 73 Pin 1 is 12.98 Pin 2 is 6.85 Pin 3 is 0 Pin 4 is 0 Pin 5 is 1.21 Pin 6 is 1.21 Pin 7 is 0 Pin 8 is 0 Pin 9 is 6.6 Pin 10 is 13.71 I have a question though, in the schematic, it shows pin 2 should be 2.94 and mine is way higher.
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Post by husker on Jan 15, 2018 23:34:28 GMT -5
Lol, oh sure just destroy my idea . Any other thoughts about this thing? I really don’t want to toss it in the scrape heap How about something REALLY simple? Have you tried a different microphone? Maybe the receive wire is intermittent. Simple thing #2 Check the speaker switch. My 2000 has a dirty switch and occasionally I have to jiggle it to get full speaker connection. Simple thing #3 Check speaker wire/jack/plug. Am intermittent there can cause the volume to cut out. So tonight I figured it was time to re check all the voltages. Seems pin 2 in the audio chip is way to high. It should be 2.94, its reading 6.85 during the actual volume issue. And guess what..NO PA at all....so it *appears* the 7222 is bad?
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Post by husker on Jan 15, 2018 22:32:35 GMT -5
Lol, oh sure just destroy my idea . Any other thoughts about this thing? I really don’t want to toss it in the scrape heap How about something REALLY simple? Have you tried a different microphone? Maybe the receive wire is intermittent. Simple thing #2 Check the speaker switch. My 2000 has a dirty switch and occasionally I have to jiggle it to get full speaker connection. Simple thing #3 Check speaker wire/jack/plug. Am intermittent there can cause the volume to cut out. 1. Yup, I tried that today just for the heck of it. 2. Yup, I even tried a set of headphones. No difference 3. Yup, again tried a headphones which if I am reading that right comes before the speaker jacks correct? How about the squelch circuit?? Could that be drawing down the audio?
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Post by husker on Jan 15, 2018 20:19:54 GMT -5
Actually no, lol, it was a post where a guy had lost his audio. I mean, at this point what do I have to lose? Not much, but when you consider that the audio amp IC is also used for transmit modulation, and that seems to be working, I have a hard time believing that that cap would cause receive audio issues but not transmit modulation as well. Lol, oh sure just destroy my idea . Any other thoughts about this thing? I really don’t want to toss it in the scrape heap
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Post by husker on Jan 15, 2018 19:31:53 GMT -5
here is the post..
Need a little Help here... My cobra 2000 all of a sudden stopped receiving or tx on AM
Check C174, 175, 179, and 181 for shorted/leaky. My guess is that it's C179. If it's bad, replace it with an electrolytic cap, not a tantalum. Good luck & 73s.
his answer
he audio problem is fixed c179 fixed it.....
Don't know if it will help, but i am kind of at my wits end here. The strange thing is my radio has a tantalum in it, but the service manual says it should be electrolytic
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Post by husker on Jan 15, 2018 19:26:18 GMT -5
I will clean the squelch as well, and yes, I can transmit and it shows out bound audio just fine ( the watt meter and modulation meter both move). But the muted audio mimic the sound of changing channels using the channel selector. When the flacky issue pops up, if I turn the channel selector knob, there is no change in noise in other words it is muted. Have you ever heard of the C179 thing before? Replacing the tantalum with an electrolytic? I am also going to try using headphones just to see what that does. Coincidentally (or not so), C179 is the 2.2uF tantalum cap that fails in the Cobra 138/139XLR, and replacing that with an electrolytic is recommended. So I'm thinking that you've got that mixed in with info for the Cobra 2000, so I don't think that applies here. Actually no, lol, it was a post where a guy had lost his audio. I mean, at this point what do I have to lose?
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Post by husker on Jan 15, 2018 14:28:16 GMT -5
Guess what.....after running all evening and most of today...it's back. And this time I think it is the channel selector..I think it is because when I change the channel there is no change in audio volume, it is muted. I jiggled it and the normal sound came back at times. Other times it doesn't come back. I pulled c232 and the result was zero audio. But I am pretty sure it is in the lock circuit. So how do I disable it? If you think the unlock circuit is kicking in, try keying the mic. if it still transmits, then the unlock circuit isn't the issue. If you lose receive audio, try modulating your transmit. If transmit modulation is still good, then the audio amp (IC6) is ok and the problem has to be further back in lower receive audio stages. Squelch circuit (dirty squelch pot?)? I will clean the squelch as well, and yes, I can transmit and it shows out bound audio just fine ( the watt meter and modulation meter both move). But the muted audio mimic the sound of changing channels using the channel selector. When the flacky issue pops up, if I turn the channel selector knob, there is no change in noise in other words it is muted. Have you ever heard of the C179 thing before? Replacing the tantalum with an electrolytic? I am also going to try using headphones just to see what that does.
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Post by husker on Jan 15, 2018 4:05:32 GMT -5
Also I read about replacing c179 with an electrolyte cap. Say 22uf by 25 volts. Ever heard of this?
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Post by husker on Jan 15, 2018 0:52:06 GMT -5
and that issue was just a broken solder connection to the coax connector! Simple fix for once!!!! Intermittent coax connections can play havoc with both receive and transmit. Worse yet, they can make you think more serious issues are the culprit. Hopefully everything is ok now. Guess what.....after running all evening and most of today...it's back. And this time I think it is the channel selector..I think it is because when I change the channel there is no change in audio volume, it is muted. I jiggled it and the normal sound came back at times. Other times it doesn't come back. I pulled c232 and the result was zero audio. But I am pretty sure it is in the lock circuit. So how do I disable it?
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Post by husker on Jan 14, 2018 17:24:32 GMT -5
and that issue was just a broken solder connection to the coax connector! Simple fix for once!!!! Intermittent coax connections can play havoc with both receive and transmit. Worse yet, they can make you think more serious issues are the culprit. Hopefully everything is ok now. No doubt! Guess I never would have thought to check the coax. But day two and still working perfect.
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Post by husker on Jan 14, 2018 1:36:46 GMT -5
and that issue was just a broken solder connection to the coax connector! Simple fix for once!!!!
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Post by husker on Jan 14, 2018 0:08:43 GMT -5
it's been running like a champ for an hr so. I will clean it here in a bit. I do have a .005 disk cap to put c132 back to a closer value, but its a 500v one. Could I still use that? Or wait until the 59v volt part comes in? The original value is .0047 59v. The value of that part is not critical. You can always use a cap rated for a higher voltage, but never a lower one. The only issue might be the physical size of the higher value part not fitting in the board. OMG...................ok...so I figured out the issue I *think* because I can reproduce it. The "radio" side of my amp's coax connector seems to have a SHORT. I was moving all my radios etc. to a new bench. That's when the Cobra stopped working again. I keyed it and the meter (its on the out bound side of the amp) didnt move at all..So I connected the coax directly to the meter which then goes to my low pass filter. When I went direct and cut out the amp, everything works awesome. If I connect to the amp, the volume dies ... So now I need to try to see what the issue on the amp is!! lol, if its not one thing it's another!!!! So you guys know Kenrich 400's at all
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Post by husker on Jan 13, 2018 22:12:52 GMT -5
it's been running like a champ for an hr so. I will clean it here in a bit. I do have a .005 disk cap to put c132 back to a closer value, but its a 500v one. Could I still use that? Or wait until the 59v volt part comes in? The original value is .0047 59v. The value of that part is not critical. You can always use a cap rated for a higher voltage, but never a lower one. The only issue might be the physical size of the higher value part not fitting in the board. Wow...I cleaned it real well, now it actually moves rather easily when I turn it. I have got it running again, this time it didn’t have the volume issue when I started the radio. Here’s crossing my fingers!
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Post by husker on Jan 13, 2018 19:38:38 GMT -5
Is it possible to clean it with contact cleaner? Absolutely! it's been running like a champ for an hr so. I will clean it here in a bit. I do have a .005 disk cap to put c132 back to a closer value, but its a 500v one. Could I still use that? Or wait until the 59v volt part comes in? The original value is .0047 59v.
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Post by husker on Jan 13, 2018 18:44:17 GMT -5
ok, so I power it up, the volume stays "hung" if you will at about 1/2 up. I can't turn it down, but I can make it a little louder if I turn it up. At the moment pin 6 is 8.1vdc That's starting to sound like a dirty volume control pot...... Is it possible to clean it with contact cleaner?
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