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Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 250
Registered: 4-2006
| | Posted on Friday, July 07, 2006 - 2:10 pm: | 
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Hi. OK, I picked up a 2000 GTL real cheap. Initially it did not even power up. I fixed that and a few other things. AM seems to work fine (A little low on wattage (Does 3, swings to 10), however, when I go to SSB (LSB, or USB, doesn't matter). The Modulation meter is at 100%. When I go to talk, the whole unit dims, the modulation meter moves backward, and the frequency counter wil eventually go to some zeroes and stay stuck like that. On a watt meter in SSB it does 3-10 watts. Any thoughts on why the unit freaks in SSB? Thanks. |
Chad
Advanced Member
Username: Chad
Post Number: 968
Registered: 11-2004
| | Posted on Friday, July 07, 2006 - 3:33 pm: |
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KV would be your man... BUT... Is there any hum in the audio? It may be time to replace the filter and other electrolytic caps.
Chad |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 251
Registered: 4-2006
| | Posted on Friday, July 07, 2006 - 4:24 pm: |
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The filter? What and where is this? |
Chad
Advanced Member
Username: Chad
Post Number: 969
Registered: 11-2004
| | Posted on Friday, July 07, 2006 - 5:35 pm: |
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The filter caps in the power supply, After time they will "dry up" and no longer properly do their job. Under load, there may be ripple on the supply and provide the things that are wanting to see pure DC, like the freq counter, an AC component riding on DC and freak it out a bit.
I replace A LOT of filter caps in a lot of different gear, it's been a few years since that was produced, it may be time.
I prefer caps with higher temp ratings 105 deg centigrade to be exact.
Honestly, again, Matt (KidV) may be able to narrow it down more, he knows the guts of these much better than I do and may have a more exact answer that may be unrelated to mine. I'm sure He'll chime in, There is Cobra 2000 in the header, he's on it 
chad |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1894
Registered: 9-2004
| | Posted on Sunday, July 09, 2006 - 1:57 am: |
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thanks chad, im not sure if my reputation preceding me is a good thing or not, but you are right, if the header says 2000gtl, im probably going to join the discussion.
chad is right about electrolytic capacitors needing replaced in older gear.
since most of the stuff i like is from the '70's, i end up replacing a lot of them.
see, other caps like ceramic discs, and mica caps use a dielectric that doesnt "dry out" nearly as fast as electrolytics do.
i replaced ALL of the electrolytic caps in my 2000. (there are 69 i think)
the reason i replaced them all, is because when a certain one goes, it will cause a problem that is hard to diagnose, and it will lead to a lot of head scratching.
there are a number of elec. caps in this radio that are rated at 10 volts, and they have a reputation of being the first to go.
if you replace one, be sure to replace it with one of a higher voltage rating. 16volts or more.
i usually go with 25 volt parts because they will still fit, and provide a measure of safety.
so, it COULD be a bad cap, but i cant recall hearing of this exact problem being discussed before.
so lets start here:
the "filter" chad is referring to is the elec. cap that filters the power supply's voltage going to the PC board.
this cap is located on the underside of the board. (take off the bottom cover)
you will see a cap in a metal bracket.
just replace this cap as it was underrated from the factory and should be upgraded even if it is working.
replace it with a 6800uF 35 or 50volt cap.
the best way to see if your problem lies in the power supply is to hook the unit to an external supply and see if the problem goes away.
BTW, how did you get the unit to turn on?
back to your problem.
i can tell you that the modulation meter should not be moving on SSB. (make sure its not set to SWR first)
if it is, im gonna guess that you have a carrier on SSB.
(make sure you are in LSB or USB mode)
hook up an external wattmeter to the radio, turn the dynamike all the way down, key the mic and watch the wattmeter.
if it moves at all, there is a problem. (it might bump upon keyup, but should stay at zero)
if it shows wattage out, turn VR4 (front middle of the board) until the needle drops to zero and shows no carrier on SSB.
turn the dynamike back up, key the mic and say, "ahhh" into it.
adjust VR11 to about 12 watts.
well, how are we doing?
give me a progress report after you have done all this.
and try to give as much detail as you can in your descriptions of what is happening. it really helps.
remember that this is an old radio, and one that people really like to get inside and mess with.
so you may encounter more problems as we go.
the total cost for all the caps to "re-cap" the radio is about 20.00 from mouser electronics.
if you plan on making this your main base station, i highly recommend replacing all of them, you'll be glad you did.
the radio will need a full alignment after doing this, but you are in luck!
you happen to live very close to someone who knows these radios WAY better than i do.
his name is pat00, not sure if you know him or not. LOL
he can be a big help to you in this matter, but he's a busy guy so ask nicely.
and whatever you do, DONT tell him matt sent you. J/K!
lots of fun to be had with this radio, working or not.
good luck,
matt |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 255
Registered: 4-2006
| | Posted on Sunday, July 09, 2006 - 10:55 pm: |
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Hi Kid. Thanks for the info. I should be able to do the alignment after. But what i don't understand is why would an alignment be needed if all I'm doing is replacing caps? It's not like I am adding extra channels or anything.
Wow, 69 capacitors. That's alot of desoldering and soldering. Only $20 for 69 capacitors from Mouser? that sounds good. How about if I go to Radio Shack? I know, I know, but it is quicker for me to just walk in and buy it. Thnaks again for the help so far. |
Coyote
Advanced Member
Username: Coyote
Post Number: 823
Registered: 11-2004
| | Posted on Monday, July 10, 2006 - 8:53 am: |
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Mouser can have them to you in a couple of days and will have everything you need in one shot. RS is very unlikely to carry every cap you need. At least thats been my experience in try'n to get component parts from RS.
Good luck,
Coyote |
Chad
Advanced Member
Username: Chad
Post Number: 971
Registered: 11-2004
| | Posted on Monday, July 10, 2006 - 8:47 am: |
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Heh I just replaced around 4000 caps in an old Amek recording console. When I was done All I could say and think was "Beeble, Beeble, Beeble, Baahhhhh... Noooo more caps!"
Chad |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 257
Registered: 4-2006
| | Posted on Monday, July 10, 2006 - 4:22 pm: |
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Replaced 4000 caps??? Darn, that is 16,000 solder points. 2 points to remove an old capacitor, and 2 points to put a new one in. A total of 4 solder points per capacitor change. 4000 times 4 is 16,000. WOW.... I'm surprised you're not in the crazy house. Incidentally, how long does something like that take? Thanks. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 260
Registered: 4-2006
| | Posted on Monday, July 10, 2006 - 7:19 pm: |
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Hi Kid. Well I was about to embark on my mission. I have the bill of material here for the Cobra 2000, and figured "Hey, what the heck, let's iorder some caps and replace them". Well, when I went to the mouser electronics website, and well,,,,,,,,,,,,,, To simply finally end up trying to find a particular capacitor is a process,,,,I have to type in and pick specific properties on their website before the part finally comes up.
Are there standardized part numbers for these capacitors? On my bill of material for the cobra 2000 there is the dynascan part number and the values of that part, but isn't there a universal part number for different electronics parts? Thanks again. |
Chad
Advanced Member
Username: Chad
Post Number: 975
Registered: 11-2004
| | Posted on Monday, July 10, 2006 - 10:10 pm: |
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Jameslarson Sed:
"Replaced 4000 caps??? Darn, that is 16,000 solder points. 2 points to remove an old capacitor, and 2 points to put a new one in. A total of 4 solder points per capacitor change. 4000 times 4 is 16,000. WOW.... I'm surprised you're not in the crazy house. Incidentally, how long does something like that take? Thanks."
Chad:
I have about 150 hours in that console. It has made world class recordings in a very popular concert hall, so regularity is key It is a Problem Child, needing recapped in 10 years since the prior re-cap. It's class A and runs quite warm, it's in a warm studio too.... I spend a lot of time inside that bad boy 
Soon it will be replaced with a Digital console, we are working out Mic Pre's now and using them on the Amek, if all goes well I may have a bunch of Rupert Neve Pre's soon ready for a home!
As for being nuts... I don't even want to know how many solder joints I have re-worked in my live Some call me crazy, it could be the Lead BUT, I do have several nice re-work stations with power vacuum de-solder pumps!
As for your reply to Matt..... I use either Nichicon 105 Deg caps or Panasonic 105 Deg. They have proven well. On Mouser it's easier to search "nichicon 105"... etc. Know whether it's Axial or radial and go nuts!!!
Chad |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 261
Registered: 4-2006
| | Posted on Monday, July 10, 2006 - 10:43 pm: |
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I know I just posted 2 things, but here is a third. When i am looking for these capacitors, what is the difference between Bi-polar and non polar capacitors? Is this the same as when a capcitor has a "hot" side and must be installed a certain direction, kind of like a diode must? Thanks. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1901
Registered: 9-2004
| | Posted on Monday, July 10, 2006 - 11:01 pm: |
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ahh yes, the mouser site. she's a bit of a beast to navigate aint she.
the secret is to click on the icon that will allow you to view their catalog online in PDF format.
then you just find the pages that list the caps.
i can tell you that they are all on one page, and you just need to write down all the part numbers or add them to your cart.
as for radio shack. that would end up very frustrating, as they wont have even half of the caps you will need. and the ones they do have they wont have enough of.
plus, they cost about 2.00 per cap!
before you order your parts from mouser, check out this thread.
these are upgrades pat00 showed me, and the cap increases work great. well, all the mods work great, but which ones you do is up to you.
but definitely increase the values of the caps listed.
http://www.copperelectronics.com/cgi-bin/discus4/show.cgi?tpc=34&post=102562#POST102562
http://www.copperelectronics.com/cgi-bin/discus4/show.cgi?tpc=34&post=90428#POST90428
and remember not to use any voltage ratings less than 25 volts.
the smaller values you just wont find in voltages less than 50 or so, so its not a problem there.
i'll try to post a link to the catalog page, but it may not pass mustard. here goes:
http://www.mouser.com/catalog/626/546.pdf
either way, its page 546 in the catalog.
well, good luck, feel free to email me if you get stuck.
one hint, using solder braid "solderwick" will make your life easier.
chad, 4000?!!!!!!
OMG!
you must tell me your process, because its got to be VERY efficient!
and you're german too!!!
later,
matt |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 262
Registered: 4-2006
| | Posted on Monday, July 10, 2006 - 11:42 pm: |
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O yeah,,1 more thing...What exactly do you mean by volting the final? Can you tell me what you do exactly to volt it...Step by step? I think i have an idea of what you mean, just let me know. Thanks.
PS--I hope I am not coming off as a newbie here. I have no problem modding boards, replacing parts, etc...I was really into this years back, I even took 2 years of electronics and graduated top of my class.... But that was a long time ago. I need to brush up as I have forgot some things....Thanks. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 264
Registered: 4-2006
| | Posted on Monday, July 10, 2006 - 11:29 pm: |
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hey Kid. Instead of using wick, I have an all in one solder gun. the one where it has the "vacuum sucker" built in. It's a one handed device. You've seen it I'm sure. Thanks for all the help. you rock. Incidentally, what is an easy way to tell where the leads are on the other side of the PC board? in other words, I can see and find the capacitor on the parts side, but then how do i easily find it's 2 solder points on the other side? I've tried shining a flashlight directly from the other side with limited success. Any ideas? Again, thanks so far. |
Chad
Advanced Member
Username: Chad
Post Number: 976
Registered: 11-2004
| | Posted on Tuesday, July 11, 2006 - 9:05 am: |
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KV, It was a mixing console so there were 40 duplicate channels I would do one value at a time, Like all the 100uF 6.3's then all the 10V then...... After the second out of 40 you get a process and your brain goes numb, just chug away, listen to some tunes.
Fella's that's just one console out of hundreds I have worked on, after a while it just becomes your life and you get quite accoustomed to burns on the tips of your fingers
Chad |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 265
Registered: 4-2006
| | Posted on Tuesday, July 11, 2006 - 12:00 pm: |
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OK Kid V., I am going to take the plunge and replace all the capacitors. In the meantime, could you be so kind as to tell me what I need to align after the replacements? In other words, what needs to be done exactly after replacing the caps. In particular, the values of VR4, VR8, and VR9 as well. I will buy you lunch  .
Thanks. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1902
Registered: 9-2004
| | Posted on Tuesday, July 11, 2006 - 5:57 pm: |
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the whole radio needs to be aligned so you will know that it is working properly.
if you dont do the alignment, you will never know if replacing all the caps actually helped or not.
its like sitting in your car at a stop light and knowing the timing is off.
its just gonna bug you until you get it adjusted right.
you are in luck!!!
i have written out a VERY detailed procedure for aligning this very chassis.
just click on this link, print it out, and read it through carefully a few times before actually doing the alignment.
here ya go:
http://www.copperelectronics.com/cgi-bin/discus4/show.cgi?tpc=34&post=113535#POST113535
here is what i would recommend you do when replacing all the elec. caps.
the other mods should be left for later when you know this radio and how it "feels" when operating correctly.
after all, you need to know what "0" is to know if you've gained +1.
1. replace all electrolytic caps on main PC board and power supply board. increase the value of C172 to 2200uF 35volts, and C18 to 680uF 25volts.
big power supply cap on bottom of radio to 6800uF 50 volts.
(dont mess with the freq. counter unless its broken. its a pain in the butt and easily ruined)
2. replace TR41 and big transistor on power supply board with NTE152's.
3. replace TR14 (2SC1674) with a 2SC2999.
put the 2SC1674 you just removed in place of TR19.
4. make sure TR24 is in the radio (2SC945)
make sure R131 (10K) is intact.
5. spray all pots and switches on the front panel with contact cleaner. (NOT wd-40!)
6. give radio a full alignment.
7. enjoy for at least a month before you decide to do anything else to it.
good luck,
matt |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 269
Registered: 4-2006
| | Posted on Wednesday, July 12, 2006 - 3:51 pm: |
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Hi Kid. I don't see a 6800UF 50v capacitor on that mouser page. The highest 50v I see is 3300UF. Any thoughts? Thanks again for all your help. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 270
Registered: 4-2006
| | Posted on Friday, July 14, 2006 - 8:54 pm: |
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Hi. Thanks for the help so far. I actually ordered the parts from mouser, and in the mean time, I got familiar with your alignment procedure.
I actually had another 2000 here that would not even power up. I got it powered up, aligned it and got it to transmit, but here is a weird thing. Even with the RF gain down, I still hear a hiss. When I turn the RF gain up, I hear the RF gain working properly, getting mixed in with this constant hiss. this hiss almost sounds like when you turn the cb on, but all you hear is background noise when no one is on. Even when I disconnect the antenna, I hear this hiss background noise. Again, it sounds like "dead air" when no one is on. Any thoughts? Also, the meter responds to transmit, but not receive. Thanks.
O yeah, 1 more thing regarding the original 2000gtl. I don't see a 6800UF 50v capacitor on that mouser page. The highest 50v I see is 3300UF. Any thoughts? Thanks again for all your help. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1301
Registered: 6-2004
| | Posted on Saturday, July 15, 2006 - 12:48 pm: |
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Too much gain the in the receiver chain. Go back over it and adjust for the best gain, but with the least noise. |
Pogo12
Member
Username: Pogo12
Post Number: 94
Registered: 3-2005
| | Posted on Monday, October 23, 2006 - 1:48 pm: |
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The fact that it dims on transmit and the frequency counter says you dont have voltage regulation on the radio.Also accounts for low wattage.First check and replace the voltage regulator.This assumes someone has not played with the circuits of course.Also look at the traces on the bottom of the radio very carefully.You would be suprised how many times I have found solder splatter on the board causing circuits to cross.Ive also seen cases of a mistuned Oscillator causing the frequency counter to run down(backwards to zero. |
Draft
Member
Username: Draft
Post Number: 88
Registered: 7-2006
| | Posted on Friday, November 03, 2006 - 9:14 am: |
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Unrelated question, but didn't think it warranted a new thread. Can anyone tell me where to find a new cover (particle board) for the 2000GTL? I have tried all of the internet auction sites to no avail. Any help would be greatly appreciated. 73s, --Rich |
Tecnicoloco
Member
Username: Tecnicoloco
Post Number: 98
Registered: 4-2003
| | Posted on Saturday, November 04, 2006 - 10:48 pm: |
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Hi Draft:
That auction site is one of the options,the other is to fabricate a new cabinet.
I seem some of my friends down here in my country have a carpenter fabricate new covers for the Cobra 2000GTL,they came up pretty nice looking and more sturdy than the factory ones.
They take the grill covers and placed on the new one with a little touch paint and they look awesome.
My 2 Pesos
Tecnicoloco
CEF-117
Sonora,Mexico. |
Draft
Intermediate Member
Username: Draft
Post Number: 112
Registered: 7-2006
| | Posted on Sunday, November 19, 2006 - 2:55 am: |
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Tecnico,
Can you somehow link me to those fabricators?
Thanks,
--Rich |
Teham
Intermediate Member
Username: Teham
Post Number: 109
Registered: 1-2004
| | Posted on Sunday, April 03, 2011 - 7:00 am: |
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OK GUYS. There is a cap in the power supply that needs changed. When u tune one of these up it isn't big enough. Replace it with twice the size. I don't remember what it is but if it is a 1600 mfd@ 35v go to a 3600 mfd @ 50 volts. should cure the problem. tony/n5jva/cef 259 |
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