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President Madison won't power on

Discussion in 'CB Radio Modifications' started by Jim Dickey, Jul 14, 2017.

  1. Jim Dickey

    Jim Dickey
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    I'm confused.

    A working radio on all three modes with a broken clock is a basket case? It sounds great on the scanner and appears to be on frequency. But I won't know for sure until Amazon drops off the freq counter on Monday.

    I thought a basket case was one of the 10 CBs I have in a pile that smoke when you plug them in? This thing appears to have better receive than a brand new 980SSB I bought two months ago, and transmits fine as far as I can tell.



    Perhaps my standards are too low for 40 year old equipment.
     

  2. Robb

    Robb
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    Yup

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    When one gets old radios, they are often dirty, out of alignment, needing new caps, as well as both cosmetic and physical maintenance needed.

    If you are set on doing this yourself, you can do it. But you will need to move slowly and be sure that each part is done with care and patience. And no small lack of test gear and knowing how to use it. That is the real challenge for you, unless you have and can use the gear.

    loosecannon is a fan of the Madisons and has rebuilt and restored his share of them. As well as repairing, restoring, and rebuilding many other kinds of radios.
     
  3. Jim Dickey

    Jim Dickey
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    I did a recap on a 139XLR a few weeks ago, turned out ok after a few stumbles. It took 3 hours but I did them one at a time and other than one that went in backwards and was later fixed, it was pretty straight forward. I think they are very similar circuits but then again Google taught me pretty much everything I know about CBs.

    I suppose the clock not working is a big deal to anyone that would pay real money for a collector piece. I'm planning on flipping the 139 and keeping this one for personal use now that it doesn't sound like a full restoration is worth my time.
    I'm not an electronics engineer, just a new tech class operator with a scope and a soldering iron. The clock is coming out and the freq counter and arduino VFO LCD display is going back in its place.

    I apologize in advance if this upsets the restorationists, on my limited budget it doesn't sound like I can afford to make this thing look 40 years newer.
     
  4. loosecannon

    loosecannon
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    No worries Jim. I for one am certainly not a purist and i own what is most likely the most modified Madison in current use. I am a huge fan of this radio and all things President as Robb noted.

    My definition of a basketcase radio is one that has a dubious history, shows up with a few hacks in it, and displays a new problem every time you fix one.
    It is certainly not an insult of your particular radio.

    You have to understand that about once a month someone comes on the forum with an absolute gem of a radio and the internet has convinced them that anyone with a soldering iron and a set of small screwdrivers can repair a CB radio.

    Sometimes they actually do end up with a nice working radio, but more often than not they just sort of stop posting about a particular radio after starting the repair process.
    Without knowing what happened, we usually assume that they buggered the radio in some way and are too embarrassed to come back on the forum and admit it.

    My goal is to save as many of these old gems as possible, and that is why i tend to give a few grave warnings to new members who are about to fall down a bottomless rabbit hole of radio fun and frustration.

    the fact that you actually have an oscilloscope speaks highly of your seriousness, and if you know how to use it you will find it very helpful in your repairs.

    you can indeed make that radio like new again on a limited budget. get a cap kit from
    Klondike Mike on Ebay, get some good contact cleaner, some windex, and start looking for a good shop to align it once you are all done.
    Sure, you can attempt the alignment yourself, but the amount of test equipment required can be cost prohibitive if this isn't something you are going to be doing a lot of.

    be sure to check out cbtricks.com and look for all the tech bullitens and updates for the SSB UPD858 chassis (both your 139XLR and your madison use this board).
    check your serial numbers and make the changes accordingly.

    also, this particular PC board is prone to cracking so be careful when working on it.

    re-cap first because of age, and then move ahead from there.
    LC
     
  5. Robb

    Robb
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    Yup

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  6. Jim Dickey

    Jim Dickey
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    LC, I appreciate your concern for trying to maintain some of these great radios as the number of them is dwindling. I didn't know they sold cap kits. I bought a big 35/50v assortment and replaced caps with that. Kit probably would have been easier
    CBs were kind of the next step for me on the list of self taught electronics skills. I started with fm transmitter kits, then amplifiers, then started designing and building my own once I understood inductors, capacitors, and acid washing pcbs. I built a few HF CW rigs from kits, then took the schematics from those and built some Manhattan style.

    CBs seemed like an affordable way to get into transceivers, but I've only been playing with them for about 3 months now. This project is really more about learning how things work and being able to apply that knowledge to future projects.
    At this point I'm gonna offer this rig for trade to someone who has another 858 rig in similar kinda working condition. There are no modifications made to this radio as far as I can tell. I can re install the clock. Just a lot of dust inside and the previously discussed replaced caps.

    I don't need to start with a cherry '36 Plymouth to build a rat rod, but I do need something with most of the critical parts working. If anyone wants to pull this thing away from the flame, let me know.
     
  7. Jim Dickey

    Jim Dickey
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    Well the unit appears to be on frequency. I attached the freq counter with rca coax to fet4 with a 30pf cap, following 399's directions. The squeal on pa/cb mode disappeared. I think it's just some old caps that had to charge up a bit, they will all get replaced soon but other than the LSB indicator light, everything is working. I tucked the original 1/4" phone plug out of the way and put a toggle in it
    It's place for the power switch that stopped working on the volume pot.

    Don't worry, I'm not planning on doing a bunch of stuff to this radio that would make it impossible to return to original condition (other than the 4 little holes in the clock plexiglass used to mount the freq counter.) I'm hoping the external arduino vfo will allow me to get into the ham band (I'm licensed) without cutting any PLL traces. We'll see.
     

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  8. Jim Dickey

    Jim Dickey
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    Does anyone happen to have a schematic of the three switch board for CB/PA, NB on/off, and the meter switch? There's about 19 wires going into this thing and two of the switches are lousy with bad connections causing a bunch of audio issues that get better or worse when I wiggle the cb/pa and the nb switch buttons. I don't need the pa function, and I'd rather have audio working than a faulty noise blanker.

    I can probably figure it out eventually but a schematic or wire color function description would be really handy
     
  9. Jim Dickey

    Jim Dickey
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    This little guy right here:
     

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  10. nomadradio

    nomadradio
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    Sams volume CB-230 has some wire colors marked on the schemo.

    Factory diagrams almost never do.

    73
     
  11. Jim Dickey

    Jim Dickey
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    Downloaded Sams CB-230, no colors. Its kinda strange, they have a picture with the 3 switch board and all the solder points labeled with numbers, but no legend telling me what all the numbers are. It also shows a CB with a 5 pin mic socket?
     
  12. Jim Dickey

    Jim Dickey
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    schematic:
     

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  13. Jim Dickey

    Jim Dickey
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    Should I assume the empty holes in the picture are for the wires?
     
  14. Robb

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    Trace them out by using the schematic.
     
  15. nomadradio

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    Wire colors usually appear only on the schematic, never in the photos. My copy of CB-230 is AWOL at the moment.

    The empty holes did indeed have wires in them, before the board was removed from the radio. No other way to get a clear shot of that board than to unsolder the wires and remove it from the front panel.

    You'll have to link the wire color on the schemo to the Sams node number in the black square. Those are what identify the location of that wire from the schematic.

    73
     

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