| Author |
Message |
    
Cbc544
New member
Username: Cbc544
Post Number: 1
Registered: 2-2004
| | Posted on Thursday, January 13, 2005 - 6:09 pm: | 
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148 gtl taiwan model ,have no receive audio but it is receiving if I put my ear next to speaker with volume all the way up I can hear it fantly also it has no transmit or audio , rx/tx lite does change when mic is keyed I have hooked up a speaker to pa jack and there is still no audio, the same aplies for USB and LSB |
Dogfacedsoldier
Junior Member
Username: Dogfacedsoldier
Post Number: 28
Registered: 10-2004
| | Posted on Thursday, January 13, 2005 - 7:26 pm: |
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was gunna say check the swr's but i think its more than that and has me stumped |
Supernuker
Junior Member
Username: Supernuker
Post Number: 21
Registered: 11-2004
| | Posted on Wednesday, January 19, 2005 - 1:44 am: |
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Do you have another radio nearby? If so, can you hear anything on AM, LSB, USB if you key up the bad radio? |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 150
Registered: 9-2004
| | Posted on Wednesday, January 19, 2005 - 4:11 pm: |
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change out the audio amp. ic. i think its an MB3756 in that radio. you can get the part from RF parts co. if it were my radio, i would replace this and the TA7222P ic. this should clear up your problems. And turn your RF gain down next itme you pull into that truck stop!
matt |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 151
Registered: 9-2004
| | Posted on Wednesday, January 19, 2005 - 4:14 pm: |
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oh yeah, put TR-24 back in. there are much better modulation upgrades that wont blow up your radio! |
Cbc544
New member
Username: Cbc544
Post Number: 2
Registered: 2-2004
| | Posted on Wednesday, January 19, 2005 - 7:43 pm: |
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I will replace these ic parts and give it try , also this a virgin radio untouched no mods at all and I can see it key up on another radio but very low and no modulation |
Rfmister
New member
Username: Rfmister
Post Number: 7
Registered: 10-2004
| | Posted on Wednesday, January 19, 2005 - 7:55 pm: |
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Replace C95,C186,C153 and C18 with 220uF 35 volt electrolytic caps.....Leave the audio amp alone for now. Try the electrolytic caps. Im 90% sure that it will fix the 148. Its 20+ years old and the caps are dried out. Ive seen it happen regularly
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Supernuker
Junior Member
Username: Supernuker
Post Number: 22
Registered: 11-2004
| | Posted on Wednesday, January 19, 2005 - 9:19 pm: |
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Yes, try replacing those caps as Rfmister said. The MB3756 is the 8 volt regulator...forget that for now too unless you have no channel indicator or RX/TX light. Do you have an external watt meter hooked up? If so, does it dead key anything at all on AM? What does the radio do on LSB, USB?
Good Luck and let us know what you find. |
Cbc544
New member
Username: Cbc544
Post Number: 3
Registered: 2-2004
| | Posted on Sunday, January 23, 2005 - 2:17 pm: |
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have changed c95,c186 c153 i can not find c18 I also changed ta7222 since I had one here,I have gotten my receive back and the radio is keying up good but still no modulation any one know where c18 is located
Thanks Ed C |
Patzerozero
Intermediate Member
Username: Patzerozero
Post Number: 349
Registered: 7-2004
| | Posted on Sunday, January 23, 2005 - 10:08 pm: |
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still sounds like the audio amp ic-week scratchy receive & same if any xmit. should be bolted to side of case. use heat grease... |
Cbc544
New member
Username: Cbc544
Post Number: 4
Registered: 2-2004
| | Posted on Monday, January 24, 2005 - 11:35 am: |
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AUDIO IC WOULD BE THE TA7222 WHICH I REPLACED,RECEIVE AUDIO IS GOOD AND STRONG ,WATTS OUT ARE GOOD AT DEAD KEY ABOUT 4 WATTS , JUST HAS NO MODULATION ON TRANSMIT AM OR SIDEBAND |
Rfmister
New member
Username: Rfmister
Post Number: 8
Registered: 10-2004
| | Posted on Monday, January 24, 2005 - 7:39 pm: |
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It is NOT the audio Amp....It IS C-18. I will look it up for you and get back to you on it |
Cbc544
New member
Username: Cbc544
Post Number: 5
Registered: 2-2004
| | Posted on Tuesday, January 25, 2005 - 2:00 pm: |
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have found c-18 and changed it everything is working perfectly now Thanks for everyones help in this matter
Ed C |
Rfmister
New member
Username: Rfmister
Post Number: 9
Registered: 10-2004
| | Posted on Tuesday, January 25, 2005 - 6:59 pm: |
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Good deal Ed......I knew that replacing the caps would solve your problem. Alot of people just rip and tear and make the problem worse....Audio amps,while they can go bad, are pretty hearty and dont usually go bad like that. Glad it fixed your problem for you |
Supernuker
Junior Member
Username: Supernuker
Post Number: 25
Registered: 11-2004
| | Posted on Tuesday, February 08, 2005 - 8:25 am: |
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I've got a new patient here...same radio as Cbc544 above. It has receive, but transmit carrier is VERY low. A nearby radio on the bench can receive this radio perfectly, modulation and all, but the radio barely nudges the external wattmeter. I've replaced most all caps and the 2SC2166 and 2SC1969. Those two transistors (TR36 & TR38) check out good according to the voltage chart as does TR37. VR8, VR9, VR10 have no effect on output power. Also, no TX of any kind on SSB.
Thanks. |
Supernuker
Junior Member
Username: Supernuker
Post Number: 27
Registered: 11-2004
| | Posted on Tuesday, February 08, 2005 - 6:56 pm: |
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I just tested the Sideband mode on above radio to be sure and it actually does transmit a VERY small signal too. I can hear myself modulate on an adjacent radio in all modes. Rx deflects the adjacent radio's meter to about 5 s-units. External wattmeter shows NO deflection. This sounds like the final 1969, but that was just replaced with a brand new one and all voltages check out!
CEF459 out. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 212
Registered: 9-2004
| | Posted on Tuesday, February 08, 2005 - 8:47 pm: |
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have you replaced your TA7222p lately? i realize that the caps are common trouble areas, but when i am troubleshooting an unknown radio, i usually suspect the power devices first. the parts are cheap and usually available, and when you know they are good, you can troubleshoot at the component level easier.
matt |
Supernuker
Junior Member
Username: Supernuker
Post Number: 28
Registered: 11-2004
| | Posted on Wednesday, February 09, 2005 - 12:50 am: |
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If you mean IC6, the Audio Amp, it's a TA7217 on this radio. It checks out ok according to the voltage chart. Could this cause no AM carrier anyway? |
Cdn_superpower
Junior Member
Username: Cdn_superpower
Post Number: 31
Registered: 6-2005
| | Posted on Tuesday, May 23, 2006 - 12:46 pm: |
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Great news cbc......
I got a cobra 2000 with the same issue, I pray that the IC and the above mentioned caps will work for me......
Hope to hear you on the air, 73's |
Big_rigger
Junior Member
Username: Big_rigger
Post Number: 36
Registered: 8-2005
| | Posted on Wednesday, June 14, 2006 - 10:42 am: |
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try another mic |
