madison update,help needed

[mustang_gt_350]

Alright I posted a while ago about my madison not working. I have since picked up a cheap workman mic. Now that i have done this the relay clicks. So i switched to LSB and noticed rf needle does try to move when i talk or wistle into the mic (the needle is semi stuck) When i move to am and do the same the needle is not moving or atleast trying to move.

Since Im the only one around today i put my video camera in my jeep about 40 feet from my base antenna and hit record. I then got to my base and counted 1-19 while moving the mic gain from all the way counterclockwise to all the way to the stop on clockwise.. Here is the video. I'm not sure exactly what is going on? I don't know if its that much overmodulated, or if it has other issues?

http://www.youtube.com/watch?v=TFIeJMin_1g

Sorry for all of the new guy stuff. I'm just trying to learn as much as i can and would like to try to fix this radio myself.

 

[mustang_gt_350]

Link to video is fixed, sorry

 

[Robb]

Well, it looks like the Maddy has output; was it in AM mode?

Think there is a problem with the mic or its modulation circuit.

 

[mustang_gt_350]

Yup on am. The madison is the only SSB radio i have, so i'm stuck on testing with AM.

The mic works fine on my cobra 29 I have talked to a few with that radio and mic and it was reported as being fine.

I'm guessing it was a modulation problem, but i wasn't sure. I looked around on it and can't find anything cut. But i haven't looked to see if it looks like the Pot was turned up.

I really would like to get this old school rig working.

 

[Robb]

Unless you have the tools and experience; it could prove to be pretty difficult for newbee to fix a radio. Not impossible; just difficult. If you are game; then there are gurus are on this forum.

These are very popular old radios and when refurbished command a decent market value. You might consider sending it to a shop and have them repair it, re-cap it, and then give it a complete alignment. So long as the radio is in otherwise nice shape, it makes it somewhat valuable in that state.

I've repaired a few of these radios for a local that have the 858 PLL chip; about four of them recently. One of them I advised that he send out to have the caps replaced because they were all bad/poor condition and I didn't want to mess with the tedious job of re-capping. Apparently, radios made in the late seventies stored in both very hot/cold environment will effectively dry out the electrolytic caps and that will be the cause for a plethora of problems.

His Madison was in prime condition otherwise; but now it is in cherry condition after the re-capping. If you want to keep this radio - and it is a keeper especially if it has the 858 PLL - then you might consider finding a shop like Doug's Custom CB or DTB Radio or others to do all of the work.

 

[mustang_gt_350]

Unless you have the tools and experience; it could prove to be pretty difficult for newbee to fix a radio. Not impossible; just difficult. If you are game; then there are gurus are on this forum.

These are very popular old radios and when refurbished command a decent market value. You might consider sending it to a shop and have them repair it, re-cap it, and then give it a complete alignment. So long as the radio is in otherwise nice shape, it makes it somewhat valuable in that state.

I've repaired a few of these radios for a local that have the 858 PLL chip; about four of them recently. One of them I advised that he send out to have the caps replaced because they were all bad/poor condition and I didn't want to mess with the tedious job of re-capping. Apparently, radios made in the late seventies stored in both very hot/cold environment will effectively dry out the electrolytic caps and that will be the cause for a plethora of problems.

His Madison was in prime condition otherwise; but now it is in cherry condition after the re-capping. If you want to keep this radio - and it is a keeper especially if it has the 858 PLL - then you might consider finding a shop like Doug's Custom CB or DTB Radio or others to do all of the work.

It does have the 858. It has the old analog clock that doesn't work and the numbers can't be read as it looks like a gasket of some kind has fell over the numbers, the meters don't work, the volume is scratchy,the tone knob post is bent, the board is full of dust from where it fell down into the vents i still need to clean it out, and . That goes along with the problem of the modulation being messed up. I can probably replace the caps myself, and if i can't i have a friend that most deffinatly can, i think he could solder his name on a flea. But that still doesn't fix the problem of being able to fix what needs fixed with the radio based equipment that he doesn't have. The case doesn't look all that bad but i don't know if its worth all the money to put into it when i could buy a new one.

Also, i just noticed while playing with it a little when on SSB that my little baofeng set to monitor a local repeater on the 140mhz area is picking up the lsb and usb, but not any of my attempted am transmissions. It is also coming over the old tube tv in the room across the hall about 30ft away.

Edit. When i'm saying about buying a new one, i was leaning more to just picking up a mobile and using it in place of the base since they are cheaper and i can use in both the car and house.

 

[slprydk]

C179 shorts out, it is between the final bias posts and causes the very problem you are talking about. I change it in every 858 radio I work on. use a 2.2uf 50 volt to replace it.

Jim

 

[Robb]

C179 shorts out, it is between the final bias posts and causes the very problem you are talking about. I change it in every 858 radio I work on. use a 2.2uf 50 volt to replace it.

Jim

Yup, and the AM Regulator is another common problem.

The relay contacts are another area that needs attention. Use contact cleaner and a clean strip of clean, white paper between both sides of the contacts. Apply a little pressure and repeat until the paper strip comes up clean. DO not use sandpaper! These relays are rare and there aren't any new replacements available.

Don't think that is the problem; but it wouldn't hurt to deal with them all just the same.

 

[Johnno]

Yup, and the AM Regulator is another common problem.

The relay contacts are another area that needs attention. Use contact cleaner and a clean strip of clean, white paper between both sides of the contacts. Apply a little pressure and repeat until the paper strip comes up clean. DO not use sandpaper! These relays are rare and there aren't any new replacements available.

Don't think that is the problem; but it wouldn't hurt to deal with them all just the same.

And while you are in there, spray some WD40 into the pots whilst twisting them around, but don't forget to take the face off first. Also use some compressed air and a clean paint brush to blow the board down with care.
I just got a President Washington (858) myself and had similar probs, as Robb says, first check is usually that relay, then pots and switches cleaned, blow the board off (they collect a lot of dust and dirt through air vents) and if you are lucky, like I was, it will be right, if not, off to the tech with it.
I always try the simple stuff first, it is surprising how often it is something minor.

 

[mustang_gt_350]

Update.

I pulled the front panel and everything off to access the board and switches. Figuring since the volumn knob is scracthy when i turn it that the mic gain was probbaly also based on the original video with it being scratchy when i was counting and turning the knob, i pulled the mic knob and put my meter on it. It looked alright execpt for a few places when it would jump to open then 13 then settle in at like 9k ohm. So i pulled the pot cover off and cleaned it with a piece of paper and blew it out. PUt it back together and tried it with the meter. No jumps and nice and smooth the whole way now.

So here is the latest test.


M2U00502 - YouTube

I'm going to pull the rest of them and clean them all, and blow out and brush the case, board and just give it a decent cleaning.

Thanks for all of the guidance so far with pointing me to the direction of the modulation. I have been learning a fair amount the last few days. I never knew the difference between SSB and am with the dual carrier.

 

[mustang_gt_350]

another update. I hooked the swr meter to it. If on am it won't even move for me to calibrate it? i'm a little confused with that. But on ssb if i key up and talk, the meter does move. So there is still somthing going on with the am side? I tried 2 different swr meters and they both did the same thing. So i pulled the maddison from the base antenna and put my 29 in place and both swr meters worked fine off the 29. 1.2 on 40 and 1.4 on 1.

looks like something is going on with the power side of the am. I will have to hook up the power meter i guess. Maybe the original owner has it turned down to run an amp?