Image

Need Help with Uniden Madison

Have some other technical questions can't find the answer for? Come in and ask them here.

Moderator: JR Moderator

User avatar
LostinMyWorld
NEW DUCK
NEW DUCK
Posts: 3
Joined: Saturday, 07 February 2009, 13:54 PM

Need Help with Uniden Madison

Post by LostinMyWorld » Wednesday, 04 March 2009, 14:31 PM

This is the Madison with the Digital Clock. The upper and lower sideband works great. The Am Transmits but does not receive. I removed the case and discovered a orange wire located on the main pc board connected to R44 disconnected on the other end. I don't know if this is the reason it does not work on AM or not. Can someone tell me where this wire connects to. I do not have any paperwork on this unit...


User avatar
Black Lightning
Wordwide & Qualified
Wordwide & Qualified
Posts: 600
Joined: Wednesday, 20 February 2008, 21:46 PM
Radio: '78 Cobra 2000 GTL
Antenna: Super Penetrator
Name: Gary
Location: Mesa, AZ
Contact:

Re: Need Help with Uniden Madison

Post by Black Lightning » Wednesday, 04 March 2009, 20:07 PM

LostinMyWorld wrote:This is the Madison with the Digital Clock. The upper and lower sideband works great. The Am Transmits but does not receive. I removed the case and discovered a orange wire located on the main pc board connected to R44 disconnected on the other end. I don't know if this is the reason it does not work on AM or not. Can someone tell me where this wire connects to. I do not have any paperwork on this unit...
This will be the power to the clarifier, and it looks as though someone unlocked it in a rather sloppy manner. Check the center pin on the clarifier pot, trace the wire back to where it connects on the PCB. If it connects to pin 1 or pin3 of IC4 (the MB3756 on the side of the heatsink inside the radio, ahead of the audio chip), that's a good indication that the clarifier has been unlocked. Sloppy because there should be no wire now coming from the board near R44 (which is the RX voltage supply for the clarifier). Sloppy because a loose wire connected to a voltage source can allow the magic smoke to escape from inside the individual electronic parts. If there is no wire on the center leg of the clarifier pot, this is where this orange wire goes.

All that aside, this would not be a reason why the radio is not transmitting on AM. If it transmits on SSB but not on AM, look for TR41, TR42 and the capacitors near them. TR42 is a 2SC945 transistor (regular, TO92 case), and TR41 is a 2SC1419 (power in a TO220 case). These are your AM power regulators and if one is toast, no AM TX! Also, check VR10 to ensure it hasn't been turned down too far. VR10 biases TR42 which drives TR41. VR10 is the AM carrier power adjustment. Hope this helps!
Ignorance can be fixed. Stupid will present a special challenge!

Image



User avatar
LostinMyWorld
NEW DUCK
NEW DUCK
Posts: 3
Joined: Saturday, 07 February 2009, 13:54 PM

Re: Need Help with Uniden Madison

Post by LostinMyWorld » Thursday, 05 March 2009, 9:21 AM

Black Lightning wrote:
LostinMyWorld wrote:This is the Madison with the Digital Clock. The upper and lower sideband works great. The Am Transmits but does not receive. I removed the case and discovered a orange wire located on the main pc board connected to R44 disconnected on the other end. I don't know if this is the reason it does not work on AM or not. Can someone tell me where this wire connects to. I do not have any paperwork on this unit...
This will be the power to the clarifier, and it looks as though someone unlocked it in a rather sloppy manner. Check the center pin on the clarifier pot, trace the wire back to where it connects on the PCB. If it connects to pin 1 or pin3 of IC4 (the MB3756 on the side of the heatsink inside the radio, ahead of the audio chip), that's a good indication that the clarifier has been unlocked. Sloppy because there should be no wire now coming from the board near R44 (which is the RX voltage supply for the clarifier). Sloppy because a loose wire connected to a voltage source can allow the magic smoke to escape from inside the individual electronic parts. If there is no wire on the center leg of the clarifier pot, this is where this orange wire goes.

All that aside, this would not be a reason why the radio is not transmitting on AM. If it transmits on SSB but not on AM, look for TR41, TR42 and the capacitors near them. TR42 is a 2SC945 transistor (regular, TO92 case), and TR41 is a 2SC1419 (power in a TO220 case). These are your AM power regulators and if one is toast, no AM TX! Also, check VR10 to ensure it hasn't been turned down too far. VR10 biases TR42 which drives TR41. VR10 is the AM carrier power adjustment. Hope this helps!
Thanks for the help. the radio transmits on AM but has no receive on AM....

User avatar
Popcorn501
Wordwide & Qualified
Wordwide & Qualified
Posts: 937
Joined: Wednesday, 17 January 2007, 19:36 PM

Re: Need Help with Uniden Madison

Post by Popcorn501 » Friday, 06 March 2009, 8:06 AM

Did you check your speaker?

User avatar
Hisarm
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Monday, 09 March 2009, 15:27 PM
Name: Armand
Home Phone: 8028925376

Re: Need Help with Uniden Madison

Post by Hisarm » Monday, 09 March 2009, 17:40 PM

Check your PC Board Number right in the front of the radio. If it is PC-411AD, it has the MB-8719 PLL IC, and resistor r44 is the 8.14V feed for the clarifier. The center wire on the clarifier should be blue, and one side is red, the schematic shows the wire on the other leg going to r44, but it doesn't say what color it is. Check to see if you have appx. 8.14V on that orange wire with a DC volt meter, and if you do, that's probably the clarifier wire. Hope this solves the problem!
Hisarm


Post Reply Previous topicNext topic

Who is online

Users browsing this forum: No registered users and 1 guest