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Message |
    
Kid_vicious
New member
Username: Kid_vicious
Post Number: 3
Registered: 9-2004
| | Posted on Saturday, October 09, 2004 - 8:26 pm: | 
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i recently won a pres. madison on ebay. its the old one with the 858 chip. i have a few questions. first, the s-meter wont fall to zero. it sits at about 1 s unit, when a strong signal comes in, it tries to move but just vibrates in place. is the meter itself bad? or is there a part that has gone? the meter works normal on TX.
second, there is a channel mod done to this radio that seems odd to me. it starts like the standard two switch mod, but, well, it goes like this: the trace to pin19 is cut and bridged with a 4.7k resistor. a wire attatched to this resistor is going to the NB switch. nothing done to pin 20. pin 21's trace is not cut, but there is a diode going from pin 21 to the NB switch. the switch does change the channels but i dont know where i am. anyone heard of this mod?
i think the final and driver are weak in this radio; what are some good replacement options? does motorola make a final for this radio? also are there any other circuit upgrades i should know about? i am trying to restore this radio to 110%, so any help is much appreciated. thanks in advance. |
Dindin
Intermediate Member
Username: Dindin
Post Number: 416
Registered: 2-2004
| | Posted on Sunday, October 10, 2004 - 9:08 am: |
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Kid_vicious,firts thing I would suggest on restoring the Madison is to get a copy of Sams photo-facts vol#CB-179 for the 858 version or vol CB-230 for the first Uniden version.they are available on the internet for a fair price if you shop around.that mod does sound different.I wouldnt try transmitting with it till I put a freq counter on and found out where it was transmitting because your probley not that far from the 10 meter ham band.on the meter it sounds like a 1n60 type diode bad in the metering circuit.cant find my sams to tell you which one most likley.I'm sure motorola makes a suitable replacement for the final but a Toshiba 2sc1969 wouldnt be hard to find.hope this little bit helps |
Kid_vicious
New member
Username: Kid_vicious
Post Number: 5
Registered: 9-2004
| | Posted on Sunday, October 10, 2004 - 6:48 pm: |
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thanks dindin,i read last night that a meter can get static build up after years of use. they suggest rubbing it with some water and a little detergent. thumping it a few times brought it down, but as soon as i keyed and unkeyed the mic, it wouldnt lower past s-1.
i looked inside the radio last nite and it seems the final and driver have been replaced. the final looks like a 1969 (hard to see) and the driver is an SK number(dont remember it). i will look for the sams book, but i already have the alignment procedures. i'm looking for tricks and upgrades that people have found over the years. i found an npc-rc mod for it, but i've been reading bad things from people about that mod. hope some of you techs arent too sick of answering the same old questions on this radio, but i did a search and couldnt find much. thanks again. |
Kid_vicious
New member
Username: Kid_vicious
Post Number: 6
Registered: 9-2004
| | Posted on Tuesday, October 12, 2004 - 8:10 pm: |
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well the freq. mod takes me to 27.455 on ch.8 and goes to ch 40. 27. 805 i think.
i cant seem to find any receiver mods, am detection mods, or semiconductor upgrades any where on the net. any links you techs could provide would be much appreciated. |
Tech808
Moderator
Username: Tech808
Post Number: 3804
Registered: 8-2002
| | Posted on Tuesday, October 12, 2004 - 10:00 pm: |
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Kid vicious,
Look to the LEFT of the Forum here and you will see:Tools then under that you will see: Modification List CLICK on it and then go to President Madison.
There you will find Tune up information and also Mic Circuit modifications as well as Mods for the Transmit circuit that I have posted.
NOTE!
You will find mods for BOTH the MADISON with the 858PLL and the MADISON with the 8719PLL depending on which Model you have.
Hope this helps,
Lon
Tech808 |
Kid_vicious
New member
Username: Kid_vicious
Post Number: 7
Registered: 9-2004
| | Posted on Tuesday, October 12, 2004 - 10:32 pm: |
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thank you so much lon! i had seen the tune up list you mentioned before, but i guess i didnt scroll down in the notes section.
Do you think i should just replace the meter? i have an old junker 139xlr with a good meter in it, but i dont want to crack it loose unless its going to work.
sorry, two more questions. how much voltage is going to the meter lights and the clock lights?
i need to replace them.
i have heard that the 2sc1419 transistors are junk, there are three that i can see in this radio. can/should i replace all of them and what is a good replacement? thank you for all your help. |
Kid_vicious
New member
Username: Kid_vicious
Post Number: 8
Registered: 9-2004
| | Posted on Tuesday, October 12, 2004 - 11:41 pm: |
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hey lon.(or any other tech that reads this)
after reading through the mod list and comparing similar chassis; i have a couple of questions.(hope im not being a naive bother).
here goes: these are all ssb boards w/ the 858 chip. on the madison, you guys list
R78 as a 15K and say to change it to a 33K.
on the 139xlr, you list R78 as a 27K and say to change it to a 56K. arent these boards identical?
if so, which mod is correct?
on the madison, you guys list C174 as 56pf and say to change it to 82pf. on the 139xlr it says to change this part to 100pf. which is it?
also on the 139xlr, it says to change C173 from 180pf to 220pf. this is not listed on the madison. should it be done?
on the grant, for amc, it says VR7 or cut D23
on the washington, for amc, it says VR7 or cut D14
on the madison and 139xlr, there is no diode listed.
so, am i wrong in thinking that these chassis are the same? are there typos on the mod list? which of these mods is correct?
thank you for your help, hopefully we can get to the bottom of this as i'm sure it has confused more than a few of us "screwdriver experts" out here. |
Tech808
Moderator
Username: Tech808
Post Number: 3808
Registered: 8-2002
| | Posted on Wednesday, October 13, 2004 - 12:55 am: |
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The Chassis and Boards may be the Same in Many Radios out there but the Components are different in many of them.
The Mods that are listed for each radio are 100% Correct from the Information that I have gathered and used over the last 30+ years in the radio business and no Typos that I know of.
NOTE #1!
You also need to remember that most of the radios you mentioned above were made in Two Versions some with the 8719PLL and some with the 858PLL Under the Uniden and President name so the Mods will be different on which radio with which PLL you have.
NOTE #2
Also remember when looking in the Modification List to CHECK BOTH the President Radios and the Uniden Radios for mods as many of the Radios were made Under each name.
Lon
Tech808 |
Kid_vicious
New member
Username: Kid_vicious
Post Number: 9
Registered: 9-2004
| | Posted on Wednesday, October 13, 2004 - 5:06 pm: |
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i realize that the grant, madison, and washington, were all made with the mb8719 chip also, but i was speaking only of the upd858 versions. let me reword my question a little bit.
on my madison (upd858), should i do the C173 change? and am i assuming incorrectly that since the pll chip is the same then the other components are the same? i was under the assumption that the same circuit board was used in different radios. are my questions the same ones you hear day in and day out? i have been searching for a week now and cant find the answers i need. thanks again for your time and effort. |
Tech808
Moderator
Username: Tech808
Post Number: 3810
Registered: 8-2002
| | Posted on Wednesday, October 13, 2004 - 6:22 pm: |
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Kid vicious,
There is NO C173 listed in the President Madison (858PLL) Mods that I posted.
The mods that are listed give you the Exact parts and value to Remove and the Exact parts and value you need to use for Replacement in that Specific Radio Only.
If it says "Change C174 (56pf NPO) to a 82pf NPO)" then that is is exactly what you do if you choose to do the modification.
Personally if the radio is working great now there is no need for mods as you may not see a noticable difference in some of the mods.
Lon
Tech808 |
Kid_vicious
Junior Member
Username: Kid_vicious
Post Number: 10
Registered: 9-2004
| | Posted on Wednesday, October 13, 2004 - 7:11 pm: |
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lon, i feel as though we are not understanding eachother here. i have a president madison, and a cobra139xlr. looking at these radios side by side, they are exactly identical. why is the change of R78 to 33K in the madison and to 56K in the 139? same chassis, different part value.
i realize that there is no C173 change listed in the madison, but it is listed for the 139xlr. same chassis, why not do it to the madison?
i am not trying to be difficult, i just think we are misunderstanding eachother. |
Yankee
Intermediate Member
Username: Yankee
Post Number: 318
Registered: 7-2003
| | Posted on Wednesday, October 13, 2004 - 7:13 pm: |
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lon told the whole story in the last part of the last post.Quote: If the radio is working great now leave it alone, Uniden made a great radio when the UPD-858 PLL chip was used, I have several models of this sideband radio under different names and each one is different in it's own way and are all super performers with outstanding audio on transmit with a good power microphone. The ones I have are.
#1-Cobra 138XLR
#2-President Washington UPD-858
#3-Realistic TRC-449
#4-Realistic Navajo TRC-457
73, Carl CEF-357 |
Tech808
Moderator
Username: Tech808
Post Number: 3812
Registered: 8-2002
| | Posted on Wednesday, October 13, 2004 - 7:50 pm: |
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Kid vicious,
I have No idea what company made your Cobra or what parts they used as they have changed several times over the years with several different people making them.
EASY WAY TO DO THE MODS,
If you have a Cobra 139XLR do the Mods listed for a Cobra 139XLR ONLY.
If you have a Uniden/President Madison do the Mods listed for a Uniden / President Madison ONLY.
Lon
Tech808
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Kid_vicious
Junior Member
Username: Kid_vicious
Post Number: 11
Registered: 9-2004
| | Posted on Wednesday, October 13, 2004 - 8:35 pm: |
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thank you lon, i think that is the piece of info i needed. the fact that different companies manufactured these radios, and parts were changed over the years would make perfect sense as to why mods are different on the same chassis types. thank you, i love this forum and have gleaned a lot of info from here before i started posting. i hope that my thick headedness doesn't sway you from answering future questions; as i'm sure i will have many more. thanks again lon. |
Tech808
Moderator
Username: Tech808
Post Number: 3815
Registered: 8-2002
| | Posted on Wednesday, October 13, 2004 - 10:43 pm: |
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Kid vicious,
No Problem that is what we are here for is to Try and Help when & where we can.
Sometimes I go brain dead and over look the simple things like mentioning that the Cobra line has changed several times over the years with different companies making the radios.
Keep asking questions and the Copper Techs and Moderators and other Forum members will continue to try and help.
NOW we need to get you signed up for our CEF Radio Club so we can talk on SUNDAYS. 
Lon
Tech808 
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Kid_vicious
Junior Member
Username: Kid_vicious
Post Number: 12
Registered: 9-2004
| | Posted on Wednesday, October 13, 2004 - 11:05 pm: |
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ok lon, i'm not sure i can reach that far but i would love to join! i'll do that today! |
Tech548
Moderator
Username: Tech548
Post Number: 313
Registered: 5-2004
| | Posted on Wednesday, October 13, 2004 - 11:27 pm: |
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Kid_vicious
Go ahead and change the S-meter. If the one from your old Cobra-139 doesn't work then chances are that the problem stems from the S-meter circuit itself.
This SSB 858 board was perhaps the best-ever designed and put into a CB radio. The 858 chip will easily cover 26.085 up through 28.045 without loosing any frequencies between these two points. In my personal oppinion, this was and still is the best designed CB ever built. You do indeed have a classic.
I've been having some trouble with AOL lately but I will try to send you some modifications for this radio.
By the way...yes, the 2sc-1419 regulators are considered weak when compared to todays standards. GE-66, ECG-152 or a NTE-152 are very good replacements for the 2sc-1419 regulators.
Jeff
Tech548 |
Kid_vicious
Junior Member
Username: Kid_vicious
Post Number: 14
Registered: 9-2004
| | Posted on Thursday, October 14, 2004 - 9:40 pm: |
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thank you jeff! i guess i am lucky to have a parts radio for this madison. the reason im willing to steal parts from the 139xlr is that it has had way too many hands in it over the years. the PCB is cracked in certain areas and i think its past the point of no return! it does have a really cool feature which im not sure i want to do to the madison yet. it has a thumbwheel covaersion done to it and it will cover 26.005 to 27.995 straight through. the mod was done well but it looks pretty daunting. if anyone has the book that this mod came from maybe someone could send me a copy of the mod. thanks again guys! |
Tech548
Moderator
Username: Tech548
Post Number: 317
Registered: 5-2004
| | Posted on Friday, October 15, 2004 - 12:04 am: |
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I'd love to see that thumbwheel frequency modification also!
Jeff
Tech548 |
Yankee
Intermediate Member
Username: Yankee
Post Number: 319
Registered: 7-2003
| | Posted on Friday, October 15, 2004 - 6:24 am: |
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I have seen this conversion and if it's the same set up, It's a VFO that was being made close to 20 years ago that used the UPD-858 chip. Someone in my area has a radio with this VFO in working condition on a President Washington.
Jeff 548 thanks for the very nice words about the UPD-858 sideband radios of which I have four in like new electronic condition and I agree with the frequency range of the UPD-858 after the broad banding is done, one of mine has a Digi-Scan and two others the switch conversion, and the forth only part of the conversion is complete.
73, Carl CEF-357 |
Kid_vicious
Junior Member
Username: Kid_vicious
Post Number: 17
Registered: 9-2004
| | Posted on Saturday, October 16, 2004 - 9:02 pm: |
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i dont think this would be considered a VFO. on the top of the woodgrain case is a rectangular cut out about 1" x 3". mounted in this hole is a group of 5 numbered wheels. each numbered 0-9. the first one is stuck on 2. the second one only switches between 6 and 7, the third and fourth go from 0-9, and the fifth one is stuck at 5.
there doesnt seem to be an oscillator board in the radio. it looks to me that the ribbon cable coming off of the thunbwheels is going right to the circuit board next to the PLL. i want to do the mod, but i just got this radio and it already does .455 to .805. thats where i hang out anyway. i think it was in an old "secret cb" book. |
