I'm trying to find a picture of a component board for a cobra 25gtl. One of the Diodes went up in smoke a split, Yes SPLIT in half. So I need to know the value of this diode. It's location is D10, any help would be great. thanks.
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Cobra 25GTL
- Thread starter Mongoose
- Start date
I have a 25 gtl here as a parts units, I can't see the actual number on it but, just replace it with a 1n4002 or a 1n4007 or anything in between, it's not a critical part so any of them will work just fine.
Cobra 25 LTD:
Supertune: Replace the stock final with a 2SC1969 unit. Solder a jumper across D10 (this may cause receive distortion at high volumes, remove jumper if it does). Change R43 to 4.7 ohms. Remove C149. Place 82-150pf cap across C 46. Place 33-68pf cap across C42 (select for best output). Set VR5 half-way open. If D9 or C6 have been removed, replace them with the same values specified in the 29 procedure above. If TR14 is cut or missing, replace it with a 2SA733 unit. Spread open L8 a bit, and adjust L10 for best swing, using a loud, steady "aaaaaaah" sound into the mic. MAKE SURE to use heat-sink compound when mounting the new final, and MAKE SURE the final mount screw is tight! Optional: For more mic amplification, replace R76 with 1K ohm.
From DTB's site.
Supertune: Replace the stock final with a 2SC1969 unit. Solder a jumper across D10 (this may cause receive distortion at high volumes, remove jumper if it does). Change R43 to 4.7 ohms. Remove C149. Place 82-150pf cap across C 46. Place 33-68pf cap across C42 (select for best output). Set VR5 half-way open. If D9 or C6 have been removed, replace them with the same values specified in the 29 procedure above. If TR14 is cut or missing, replace it with a 2SA733 unit. Spread open L8 a bit, and adjust L10 for best swing, using a loud, steady "aaaaaaah" sound into the mic. MAKE SURE to use heat-sink compound when mounting the new final, and MAKE SURE the final mount screw is tight! Optional: For more mic amplification, replace R76 with 1K ohm.
From DTB's site.
I think the photo show exactly why you DON'T want to jumper it. There's a diode there for a reason.
seen many of the protect diodes go up in smoke in my time from being hooked up backwards without a fuse inline with the power cord. But this one is the anti-spiking diode .
guys have been known to jump this diode for a extra watt or so , not a very good idea. The diode is there for a reason. You might look on the bottom of the board and see if it was already jumped there ? If that's the case ? you can remove the jumper there and the fouled diode.
IM not sure why this diode would go in the first place ? but there's a good chance if you change it , it might blow again , then you will know that your true problem lyes elsewhere.
Were there any mods done to this radio ? If so ? make sure they were done right and there's no solder balls or bridges that may have caused this diode to short out in the first place. That 25GTL is pushing 30 years old (if it isn't already)
guys have been known to jump this diode for a extra watt or so , not a very good idea. The diode is there for a reason. You might look on the bottom of the board and see if it was already jumped there ? If that's the case ? you can remove the jumper there and the fouled diode.
IM not sure why this diode would go in the first place ? but there's a good chance if you change it , it might blow again , then you will know that your true problem lyes elsewhere.
Were there any mods done to this radio ? If so ? make sure they were done right and there's no solder balls or bridges that may have caused this diode to short out in the first place. That 25GTL is pushing 30 years old (if it isn't already)
The guy that it was bought from ran a 100 watter with it and I noticed when I hooked it up to my meters the dead key was 4 watts. Seems to me that is to high. Then as time has gone on when you key up, the meter on the radio would go to zero. But it works correctly when receiving. Keep in mind that the 100 isn't being used anymore. I will go to ratshack and pcki up a 1n4002 as suggested above. Hopefully that will fix the problem.
Well i put the new diode in (1N4002) and it went up in smoke instantly so there are more problems than I think it is worth.
The 21GTL uses a similar diode in that location also. Unfortunately since the hacking on CBTricks the schematic is not available for viewing. The only print I can see on the diode in mine is K2. I'm not well versed in diodes, was/is a 1N4002 heavy enough?
Like I suspected , those diodes usually don't go unless something else is causing it . This is a good word to the wise ........although you did not find any jumper , guys who do this with the anti-spiking diode are only asking for trouble in the future. All for the sake of maybe 1 watt of gain.
Thumbs up to you Mongoose You gave it a try.- No one is chatting at the moment.
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