|
|
|
|
| CB Radio Forum Discussions regarding Citizens Band Radio (CB) |
11-15-2012, 7:01 AM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Dak cb but no modulation help!
I bought a radio that seems to do everything right but has NO modulation. Recieves good, power out good 5w, but No modulation. No hum buzz when I touch the audio pin on mic socket. Tubes check good, bypassed the mic gain control but no hum when touching connections. This is a DAK CB with transistor receive and tube transmit. ANY Thoughts? There are 3 - 47microfarad caps that I'm questioning but can't test and don't have any to try. see schematic pic. Thanks Ron
Last edited by darticus; 11-15-2012 at 7:04 AM..
|
11-15-2012, 2:52 PM
|
 |
Completely Banned for the Greater Good
|
|
Amateur Radio
|
|
Join Date: Mar 2005
Location: Point Pleasant Beach, N.J.
Posts: 6,127
|
|
What schematic? Do you have a multimeter? DC voltage measurements against those given in the schematic (usually) pinpoint the defective stage and component(s). If not common sense will tell you, I hope you have those long lost tube troubleshooting skills. For example, if you find positive voltage on a control grid it's a sure sign plate of voltage from the preceding stage through a leaky inter-stage coupling cap.
Even with a schematic troubleshooting by remote control is difficult at best. A doctor will never diagnose over the telephone for that reason, an office visit is required. Bear that in mind when you get all confused by the answers sure to follow in this thread.
|
11-15-2012, 3:17 PM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Are you saying I should take voltage readings at various spots on the chassis and compare to the schematic? Would you be able to tell me where to check voltage??? I don't seem to see voltages on the schematic that I have. Thanks Ron
Quote:
Originally Posted by kb2vxa
What schematic? Do you have a multimeter? DC voltage measurements against those given in the schematic (usually) pinpoint the defective stage and component(s). If not common sense will tell you, I hope you have those long lost tube troubleshooting skills. For example, if you find positive voltage on a control grid it's a sure sign plate of voltage from the preceding stage through a leaky inter-stage coupling cap.
Even with a schematic troubleshooting by remote control is difficult at best. A doctor will never diagnose over the telephone for that reason, an office visit is required. Bear that in mind when you get all confused by the answers sure to follow in this thread.
|
|
11-15-2012, 8:56 PM
|
|
Completely Banned for the Greater Good
|
|
Amateur Radio
|
|
Join Date: Mar 2005
Location: Point Pleasant Beach, N.J.
Posts: 6,127
|
|
Your problem is in the audio chain, where else would you take them? Since there are no voltages on the schematic you have no frame of reference so I can't help you any further. No offense, your question tells me you lack basic skills so voltage readings are meaningless to you. Now you need an old school tech familiar with tube circuits.
|
11-15-2012, 9:08 PM
|
 |
Member
|
|
Amateur Radio
|
|
Join Date: Feb 2011
Location: Beavertown Pa.
Posts: 522
|
|
Quote:
Originally Posted by kb2vxa
Your problem is in the audio chain, where else would you take them? Since there are no voltages on the schematic you have no frame of reference so I can't help you any further. No offense, your question tells me you lack basic skills so voltage readings are meaningless to you. Now you need an old school tech familiar with tube circuits.
|
You are exactly correct. |
11-15-2012, 9:14 PM
|
 |
Member
|
|
Premium Subscriber
|
|
Join Date: Oct 2006
Location: Orange County, California, USA
Posts: 1,873
|
|
Quote:
Originally Posted by kb2vxa
Now you need an old school tech familiar with tube circuits.
|
What is that, like, a hundred mile drive for you to Sparta?
__________________
"'Anybody with fewer radios than me is a loser; anyone with more is a lunatic' may be the quote of the year." -datainmotion
|
11-16-2012, 5:35 AM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Who coming to help?
Quote:
Originally Posted by RadioDaze
What is that, like, a hundred mile drive for you to Sparta?
|
|
11-16-2012, 11:09 AM
|
|
Member
|
|
Amateur Radio
|
|
Join Date: Feb 2011
Location: Beavertown Pa.
Posts: 522
|
|
Santa Ho Ho Ho
|
11-16-2012, 3:39 PM
|
|
Member
|
|
Premium Subscriber
|
|
Join Date: Oct 2006
Location: Orange County, California, USA
Posts: 1,873
|
|
Quote:
Originally Posted by darticus
Who coming to help?
|
I thought it sounded like Warren was volunteering to go and help you.
__________________
"'Anybody with fewer radios than me is a loser; anyone with more is a lunatic' may be the quote of the year." -datainmotion
|
11-16-2012, 5:33 PM
|
|
Completely Banned for the Greater Good
|
|
Amateur Radio
|
|
Join Date: Mar 2005
Location: Point Pleasant Beach, N.J.
Posts: 6,127
|
|
"Who coming to help?"
Trojan Man! (You have to be a very old Greek to get that one.)
"I thought it sounded like Warren was volunteering to go and help you."
I would if I cold but I can't so I won't. Look at the map, how long would it take to get there walking with my trusty Simpson under my arm?
Last edited by kb2vxa; 11-16-2012 at 5:35 PM..
|
11-16-2012, 6:22 PM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
BY the time the help arrives i'll have this done. OH well!
|
11-16-2012, 6:39 PM
|
 |
Member
|
|
Amateur Radio
|
|
Join Date: Jan 2006
Location: Bloomington,Illinois
Posts: 5,419
|
|
Quote:
Originally Posted by darticus
BY the time the help arrives i'll have this done. OH well!
|
By the time help arrives, you could give that box a righteous burial and go out and buy a new radio and be happier that it works? 
73,
n9zas
__________________
"Whatever doesn't kill you...will make you stronger"! 
|
11-17-2012, 6:45 AM
|
|
Member
|
|
Amateur Radio
|
|
Join Date: Feb 2011
Location: Beavertown Pa.
Posts: 522
|
|
Quote:
Originally Posted by gewecke
By the time help arrives, you could give that box a righteous burial and go out and buy a new radio and be happier that it works?
73,
n9zas |
You know this is how he earns to do repairs so please don't bust his balls on this. it is how i learned many years ago. he just needs a mentor to guide him along.
K3CFC |
11-17-2012, 7:03 AM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Hey Thanks for the backup. Ron
If New is what SOME OF YOU ONLY WANT you want wait till OBAMA CARE GETS FULLY FUNCTIONAL.
GOOD BUY USA AS WE NEW IT!
Quote:
Originally Posted by k3cfc
You know this is how he earns to do repairs so please don't bust his balls on this. it is how i learned many years ago. he just needs a mentor to guide him along.
K3CFC
|
|
11-17-2012, 12:04 PM
|
|
Member
|
|
|
Join Date: Apr 2012
Location: Puget Sound
Posts: 505
|
|
I remember the DAK. Very nice radio in it's day. If anyone is trying to work on these, then there are certin things that need to happen.
1) Be at least 40+ yrs old. 2) Have a very good background-understanding of tube circuts.
3) Have a good understanding of basic trouble shooting.
4) Remember to keep one hand in your pocket.
|
11-17-2012, 2:30 PM
|
|
Member
|
|
Amateur Radio
|
|
Join Date: Feb 2011
Location: Beavertown Pa.
Posts: 522
|
|
Quote:
Originally Posted by darticus
I bought a radio that seems to do everything right but has NO modulation. Recieves good, power out good 5w, but No modulation. No hum buzz when I touch the audio pin on mic socket. Tubes check good, bypassed the mic gain control but no hum when touching connections. This is a DAK CB with transistor receive and tube transmit. ANY Thoughts? There are 3 - 47microfarad caps that I'm questioning but can't test and don't have any to try. see schematic pic. Thanks Ron
|
Check your private message on here. then decide what to do.
K3CFC |
11-17-2012, 3:25 PM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Very proud of you! Couldn't say it better! Ron
Quote:
Originally Posted by cabletech
I remember the DAK. Very nice radio in it's day. If anyone is trying to work on these, then there are certin things that need to happen.
1) Be at least 40+ yrs old. 2) Have a very good background-understanding of tube circuts.
3) Have a good understanding of basic trouble shooting.
4) Remember to keep one hand in your pocket.
|
|
11-17-2012, 5:08 PM
|
|
Completely Banned for the Greater Good
|
|
Amateur Radio
|
|
Join Date: Mar 2005
Location: Point Pleasant Beach, N.J.
Posts: 6,127
|
|
I said it first! <razz>
|
11-17-2012, 5:32 PM
|
|
Member
|
|
|
Join Date: Feb 2008
Location: Sparta, New Jersey
Posts: 660
|
|
Fixed the problem, so modulation is back! Everything done with less than a buck 50. COOL! WITH CHANGE! Thanks for all the suggestions and information. A lot cheaper than a new radio and going up in value with age. Ron
|
11-18-2012, 12:48 PM
|
|
Completely Banned for the Greater Good
|
|
Amateur Radio
|
|
Join Date: Mar 2005
Location: Point Pleasant Beach, N.J.
Posts: 6,127
|
|
So wha hoppin Lucy? Don't leave us in the dak, inquiring minds want to know.
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
 Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -5. The time now is 7:37 PM.
|
|
|
|
| |
|
|
