| Author |
Message |
    
Goat373
Intermediate Member
Username: Goat373
Post Number: 314
Registered: 3-2005
| | Posted on Monday, December 04, 2006 - 8:45 pm: | 
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ok...here we go, i have always been dissapointed with my cobra xl350 amp (2 x 2879) only ever got around 100 watts out...on CB mind you.
today i tried it on 10 meters just for s/g's nearly 300...about 275PEP...this was taken on two reliable meters. why such a differance and what can i do to fix it!! BTW, same radio and input wattage...both on USB magnum 257 at full power (32 watts pep)
27.105 =105 out
28.350 =275 out
HELP! |
Goat373
Intermediate Member
Username: Goat373
Post Number: 315
Registered: 3-2005
| | Posted on Monday, December 04, 2006 - 10:33 pm: |
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lol...im stupid, output is the same on 10 meters as it is on cb
getting about 125 after a compleate rework of my station, new coax and better swr readings.
125 watts maximum out of 2 2879's with 32 watts of SSB drive...what gives, what am i doing wrong?
its not possible for one transistor to go bad and the amp could be limping on one leg is it???
im up for suggestions, anything, at this point if you tell me unicorns are eating my power i'd prolly beleave you. im utterly dumbfounded, i even tried re-winding input and output xformers but to no avail. |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 909
Registered: 4-2005
| | Posted on Tuesday, December 05, 2006 - 4:43 am: |
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Hi Brian...long time no see. 
YES..it is very possible to have one tranny down! Been there done that and has been repaired with good results in my old 2xMRF455 Pal225.
IF you suspect one pill down there is no way I know of to check it without a transistor checker.
Look for a matched set of 2879's and when you find them let me know! Been looking to replace a dual set in my Gray300. 
Probably run around $40-50 for the pair.
Good luck!
Hank CEF559 |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 911
Registered: 4-2005
| | Posted on Tuesday, December 05, 2006 - 4:48 am: |
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http://www.copperelectronics.com/cgi-bin/discus4/board-auth.cgi?lm=1132354267&file=/34/82950.html
Lets use the "WAY BACK" machine  |
Goat373
Intermediate Member
Username: Goat373
Post Number: 316
Registered: 3-2005
| | Posted on Tuesday, December 05, 2006 - 5:49 pm: |
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thats why i dont work on amps...tube or otherwise...on the prowl for a Matched set of 2879's as we speak. |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 914
Registered: 4-2005
| | Posted on Tuesday, December 05, 2006 - 8:52 pm: |
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Good luck Brian... I wrote RFParts an email asking for info a WHILE ago with no response...maybe you'll have better luck. I've been too busy to look much further right now.
Please DO yet me know what you find.
I'll keep my eyes open as well. |
Goat373
Intermediate Member
Username: Goat373
Post Number: 318
Registered: 3-2005
| | Posted on Wednesday, December 06, 2006 - 7:27 pm: |
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rf parts hase them...for around a 50 spot |
