| Author |
Message |
    
Gtrkid68
| | Posted on Friday, October 10, 2003 - 8:01 am: | 
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WOW this is such a great forum. The users here are so helpful, especially when it came to answering my question and forwarding info about the old Cobra 139. So i've decided to try again...
I recently bought a President Zachary T with the D858 chip. I've seen this chip identified as the UPD858 or simply as the 858. Are these all the same? And will the mods that i find for one apply to anything listed as the 858 pll?
Thanks so much again for everyones help.
Dave |
Tecnicoloco
| | Posted on Friday, October 10, 2003 - 6:07 pm: |
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Yes,you are correct,there are the same PLL chips
Good luck
Tecnicoloco
73's |
Crafter
| | Posted on Friday, October 10, 2003 - 7:39 pm: |
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Yep same horse!! Easy to do a chip jump too. |
2600
| | Posted on Saturday, October 11, 2003 - 11:11 pm: |
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Just one note of caution. This chip was used in BOTH AM-only AND SSB/AM radios. The specific details to convert a AM-only radio will NOT be the same as for a SSB radio.
The SSB radios with the 858 in them all used an internal (intermediate) frequency of 7.8 MHz. This dictates the binary arithmetic used to select the 40 legal channels in the radio.
The AM-only radios used an IF frequency of 10.695 MHz. Different internal arithmetic is used to obtain the 40 legal channels in a AM-only radio, so the "mod" details like pin numbers to change, and the extra frequencies you'll get are ALL different from the SSB-radio setup.
Yes, both types can be modded for extra frequency coverage, but the instructions for modding a SSB radio will NOT work as advertised for a AM-only model, and vice versa. Gotta use the right setup to match the particular 858 radio you want to mod.
73 |
Gtrkid68
| | Posted on Sunday, October 12, 2003 - 11:57 am: |
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YES i had been aware of that from reading up on this forum, and other sites with mods. For the AM-only Zach T; im gonna shoot for whatever i can get below channel 1. Thanks again for the great info!
Dave |
Crafter
| | Posted on Monday, October 13, 2003 - 2:15 am: |
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My zach seems like I get 27.455 to 27.805 and get 26.815 to like 26.525 who knows its been on my shelf so long. |
Kc0gxz
| | Posted on Wednesday, October 15, 2003 - 7:26 am: |
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Gtrkid68
Let's slow down a bit. There are two possible conversions for that 858 chip. And both of them are for AM-only radios.
You will be working either with Pins 19 and 21 or Pins 20 and 21. The resulting frequency spectrums are not the same. And just so you know, there were two versions of the Zachary T.
Anyways, yes, they can be modified but it is rarely done because, even though they have the 858 chip, they do not have the same frequency coverage as the sideband radio did with the same chip.
They would go up a few channels above 40 but it's 98% sideband use up there anyways. So what's the point? Also, there will be many repeated channels. Too many to make it worth the bother.
I'm going to list the two frequency conversions for you. Try them both and see what you come up with. The results of conversios #2 will be frequencies above channel 40 only. No lower frequencies. Ok. Here goes.
------------------------------------------------
Frequency Conversion #1. Using Pins 19 and 21.
1- Find pin 19 on the PLL chip on the foil side of the circuit board. It will be a grounded pin in the near center of the row of pins.
2- Isolate this pin by making a cut in the foil so it is no longer grounded and install a small 1/4 watt 4.7K ohm mini resistor across this cut.
3- Mount a SPDT (center off) mini toggle switch in a convenient location on the front of the radio. (Lower front panel works for me)
4- Solder a wire from the center pole of the switch to pin 19.
5- Next, solder a wire from the top pole of the switch to board ground.
6- Last, solder a wire from the bottom pole of the switch to pin 21 which is a constant 5 volt source. Now you're done.
--------------------------------------------------
When the switch is in the center position, you will have the normal channels 1-40.
In the UP position, you will have some frequencies above channel 40.
In the DOWN position, it will only go 9 channels under channel one. This is what you can expect for low frequencies.
27= 26.875
28= 26.885
29= 26.895
30= 26.905
31= 26.915
32= 26.925
33= 26.935
34= 26.945
35= 26.955
-------------------------------------------------
Frequency Conversion #2. Using Pins 20 and 21.
This second one is almost identical to the first but a different switch is used and TWO cuts are made on "PIN 20" instead of pin 19.
An x-acto knife works best for making foil cuts. After the cuts are made, do a continuity check from pin 20 to ground and make sure there is no connection to ground.
-------------------------------------------
1- Find pin 20 on the PLL chip on the foil side of the circuit board. It will be a grounded pin in the near center of the row of pins.
2- Isolate this pin by making a small cut on BOTH SIDES OF PIN 20 in the foil so it is no longer grounded.
3- Next, solder a small 1/4 watt 4.7K ohm mini resistor from pin 20 back to ground.
3- Mount a SPST mini toggle switch in a convenient location on the front of the radio.
4- Solder a wire from the center pole of the switch to pin 20.
5- Next, solder a wire from the top pole of the switch to board ground.
6- Last, solder a wire from the bottom pole of the switch to pin 21 which is a constant 5 volt source.
------------------------------------------------
Believe me when I say that this is easier done than said.
Good luck with the frequency conversion.
Jeff, kc0gxz. |
Gtrkid68
| | Posted on Sunday, October 19, 2003 - 2:10 pm: |
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Thank you Jeff. One more thing.. You mentioned that there are two different versions of the Zach T. Care to go into more detail about that? Or is it just: one is a PRESIDENT and one is UNIDEN ? |
Kc0gxz
| | Posted on Monday, October 20, 2003 - 1:45 pm: |
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Gtrkid68
Sure. The President had the 858 chip. It wasn't until after Uniden bought out the President line that they started using the 8719 chip.
Jeff. |
Semo_rebel
Junior Member
Username: Semo_rebel
Post Number: 19
Registered: 2-2004
| | Posted on Friday, March 26, 2004 - 6:00 pm: |
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I have a question about the 858 PLL. I have a Robyn 510D SSB mobile. When I got it it had the channel conversion in it. It stopped working right. I took the wires and switches out, jumped across the cuts in the traces. On 13 it recieves at 27.515 and transmits about 3 Mhz. some channels it recieves upper channels others it recieves lowers.
Is the PLL bad or is it something else?
I have heard the PLL conversions are no good. I have been told a Expo kit is the best way to add channels to a radio. Can the PLL conversion do something to a radio like what has happened to mine or is that all just bull? |
Yankee
Member
Username: Yankee
Post Number: 61
Registered: 7-2003
| | Posted on Saturday, March 27, 2004 - 6:32 am: |
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Believe me when I say I'm no radio expert, but I have had and done several sideband radios with the UPD858 PLL, I've never run into a problem of a switch conversion going bad, I don't believe in the expo kits they are just something to take your money. Using switches the sideband only 858 PLL can do 200 channels and carry the power quite well from the low end to the high end. Sounds like the PLL circuit has a problem somewhere, could be the 858 chip, try puting the switch conversion back in and do the broadbanding that is shown on the 858 mods. on the internet. I at present have 5 of these UPD 858 sideband radios, 4 of them in working order, one of them I run in my mobile is about 28 years old , still looks like new and never been converted, still bone stock. Hope this helps. Yankee |
Semo_rebel
Junior Member
Username: Semo_rebel
Post Number: 20
Registered: 2-2004
| | Posted on Saturday, March 27, 2004 - 3:48 pm: |
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If I remember right one of the wires had come loose on the conversion, when it quit working.
We rehooked up the wire and still nothing. The guy that helped me do this thought it might have a bad crystal. He never checked to see what frequencies it was recieving just the transmit.
This was in 97 when I was was working for a cb shop at the local truck stop. This guy was one of the best radio mechanics I have ever seen. I know people who had radios modified by this guy before he died in 99 and they will not part with them for nothing.
I could try what you said, but we did hook that wire back up and it still didnt work. I am thinking that me using the radio with that wire off may have fried the PLL. |
Yankee
Member
Username: Yankee
Post Number: 64
Registered: 7-2003
| | Posted on Saturday, March 27, 2004 - 9:08 pm: |
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Rebel: I have a Uniden Grant XL that was done by the best man there ever was on any of the Uniden radios both new and older models and might never be again. after he passed away in the last 2 years several so called radio technicians want to pay the people who had radios done by this fine gentleman just to open up the radios to see his work and how he had done such a nice job. Yankee |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 697
Registered: 3-2003
| | Posted on Wednesday, March 31, 2004 - 1:39 am: |
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Semo_rebel
Double-check your soldering work on the PLL. From your explaination, this tells me that there possibly may be a couple of pins on the chip that are shorted together. Or perhaps going to ground.
Use a magnifying glass if need be. These pins are very easy to short together. In other words, in order to get "extra" frequencies from these chips, the pins are either being grounded when they shouldn't be or they are being put to voltage when they shouldn't be. Or vise-versa.
Turning the voltage ON or OFF to these pins is the job of the channel selector. It is nothing more than a ON/OFF switch for the chip. It puts X or 0 to the pins. In other words, it dials in what pins will have voltage to them and which pins wont in order to come up with a particular frequency.
To me, this sounds like a simple fix. You have either voltage to a pin when you shouldn't, OR, no voltage to a pin when you should.
Here's something that puzzled me. You said...(On 13 it recieves at 27.515 and transmits about 3 Mhz). I'm not quite sure exactly what you meant by that. Are you saying that on that particular channel your transmit and receive are 3 Meg apart from one another or what?
I highly doubt you have a crystal problem. The way this radio is acting spells PLL soldering to me. You either have a short somewhere on the chip where you shouldn't or you DON'T have one where you should.
One last thought here Rebel. I may be all wrong about this. And if so, just disregard this post because my wife says that I've been wrong about a lot of things lately. Which means, it wont come as a shock to me if you tell me that I'm way off base here.
Good luck with your project.
Jeff, kc0gxz. |
Semo_rebel
Junior Member
Username: Semo_rebel
Post Number: 29
Registered: 2-2004
| | Posted on Thursday, April 01, 2004 - 12:36 am: |
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To clarify your question. using a signal generator on chanel 13 it is recieving at 27.515 Mhz. Using a frequenct counter it transmits at 3. something MHZ. not 3 different but 3. around 3.49 Mhz exzactly. A difference of about 23 Mhz. |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 702
Registered: 3-2003
| | Posted on Friday, April 02, 2004 - 5:53 pm: |
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Semo_rebel
Just out of curiousity, what does your RF power read at this "3.49"?
You have a short or an open or a wire where it doesn't belong. Why don't you just UNDO the whole mod and start from scratch.
I don't know. To me, without seeing it, this thing spells opened or closed solder joint where it doesn't belong.
Jeff, kc0gxz. |
Semo_rebel
Junior Member
Username: Semo_rebel
Post Number: 35
Registered: 2-2004
| | Posted on Saturday, April 03, 2004 - 2:48 pm: |
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well I dont know. All I know is it did the same exact thing before I jumped accross the cut traces.
Since it doesnt do different with cut or jumped traces I think the PLL might be bad. |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 706
Registered: 3-2003
| | Posted on Monday, April 05, 2004 - 6:33 pm: |
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Semo_rebel
OK. If you have your doubts about the chip, then by all means replace the 858 and see what happens. If it was mine, I would first rebridge all "cuts" made to the board making real sure that it is all back to its original stock form.
Something just doesn't sound right here. If you end up with the same results, then you'll know for sure if you have a open or short where there shouldn't be one.
Take your time when soldering the new chip in circuit giving it ample time to cool as you solder the pins to the board. Let me know what you come up with. You have succeeded in peaking my curiousity.
Jeff, kc0gxz. |
Semo_rebel
Junior Member
Username: Semo_rebel
Post Number: 40
Registered: 2-2004
| | Posted on Wednesday, April 07, 2004 - 3:24 am: |
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I will sure tell you what I come up with, if I can find one somewhere. |
Yankee
Member
Username: Yankee
Post Number: 93
Registered: 7-2003
| | Posted on Thursday, April 08, 2004 - 4:09 am: |
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Jeff, This is starting to get interesting, it has also sparked my interest because I have several now and have done a few 858 switch conversions over the years, most of the guys only knew about channels 45-80 until I explained the full conversion to them. After that most of them said do the whole conversion. Back then the shop I was helping out at was doing the whole job including clarifier,peaking and broadbanding after the conversion for $35.00 that also included the cost of the switches, today's prices for the three switches and a pack of resistors is $12.00, I just got a set of switches the other day to do the TRC-449 mobile that's in my car. Back then the cost of the switches was less than half of today's cost. The shop was doing so many radios in the earily 80s that we stocked the switches and had the wires precut and the ends tinned. My job was to get the wires and switches ready with wires on them, each wire a different color and do the counter sales at a Cobra dealership. Yankee |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 724
Registered: 3-2003
| | Posted on Saturday, April 10, 2004 - 3:55 am: |
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Yankee
A full channel hardwire conversion on a Uniden 858 SSB chassis including the must-needed broadband power modification, clarifier, power peak, wide-banding the receiver and opening up the audio would cost a 100 bucks or more at some shops today.
It took awhile to correctly set up those old Uniden-built 858 sidebanders but when they were done, they had a lot of authority on the air back in the 70s and 80s.
When the FCC finally wised up as to what was going on and slammed the door on the SSB 858 chassis, that was the end of a marvelous CB radio. SSB Cobras and Unidens of today can't hold a candle to the old originals. And that's sad because the young and new CBers of today will never know what great radios we had 25-30 years ago.
Go away Yankee. I don't want to think about this any more. I'll probably just start crying again thinking of the sad passage of the late, great Uniden SSB 858 chassis.
Now THAT was a REAL CB radio.
Jeff. |
Yankee
Intermediate Member
Username: Yankee
Post Number: 131
Registered: 7-2003
| | Posted on Thursday, June 03, 2004 - 3:50 am: |
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Hi Jeff,
Just getting around to catching up on your interesting posts on the UPD858 sideband rigs of which I own a few nice ones.
Now I need to dig in your notes again. I need enough clarifier down slide to get a full 5KC slide and enough to clarify if someone is a little off frequency. My mobile now runs a Cobra 138XLR with the Redco Digi Scan model RDS-1 and the step switch goes a full 10KCs and not 5KCs like some digi scans I've seen. Thanks Yankee |
Tech548
Moderator
Username: Tech548
Post Number: 92
Registered: 5-2004
| | Posted on Friday, June 04, 2004 - 2:15 am: |
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Yankee
If memory serves me correctly there were a couple of ways to do this and one of them I didn't much care for at all because the end results gave you a different "center slot" for each of the 3 modes---if you know what I mean.
Give me a couple of days Yankee to dig out a few of my old my notebooks and look for the modification that you are asking for. I'll be checking back with you.
Jeff. |
Tech548
Moderator
Username: Tech548
Post Number: 109
Registered: 5-2004
| | Posted on Wednesday, June 09, 2004 - 10:28 am: |
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Yankee
I couldn't find the modification I was looking for so from this point on, I'm working from memory and what little information I do have. Note: This writers memory is known to fluxuate from time to time and therefore should not to be relied on as fact.
As you probably already know, the 858 SSB chassis used a separate crystal and varable capacitor for each mode. I don't remember what the varables were rated at but after playing with them for a while you will soon realize that their range is very limited to only 3 to 4 KCs down from the clarifiers center slot.
Now, if you have a frequency counter and don't mind experimenting a little with your old 139-XLR, here's what you can do.... CT-4, CT-5 and CT-6 are the trimmer capacitors for A/M, USB and LSB. And here we run into a problem because I do not remember which trimmer cap is for which mode. Hopefully you or one of the other forum members do. I kind of lean towards CT-4 as the A/M trimmer but I could be wrong. Anyways, for experimental purposes, the A/M trimmer is the one we are looking for because if this one doesn't give you the 5 or a little more Kc down that you are looking for, neither will the other two. Also, the A/M cap is much easier to realign.
Assuming you have determined which trimmer cap is for the A/M mode, set the clarifier at exactly center slot. With the radio set on 27.205 (chnl 20) and at normal idling or operating temperature, your frequency counter should read dead on frequency. If it doesn't, don't worry about it because we'll probably be resetting it later anyways. Now, turn your clarifier all the way to full counter-clockwise. With a non-metalic adjusting tool, see if you can tune the A/M trimmer cap down to 27.200. A little beyond that would be even better yet. If you are able to adjust it down that far (or a bit beyond), leave it right there.
Next, turn the clarifier all the way clockwise as far as it will go. Look at your counter and see if you are back at 27.205 or a bit beyond. If you are, great. If not, #$*&%+. If you weren't able to get what you were looking for, put the clarifier back to center slot and trim the cap back to 27.205.
Removing the 3 trimmers all together will allow for more upwards slide by about 2 or 3Kc but that's still not enough. And not only that, you'll end up with a different center slot for each mode.
If the above attempt failed (it worked on mine), you can always replace D-45, D-43 and D-41 with a (hard to find) Super Diode. With those, you'll end up with a 10Kc + slide and a very touchy clarifier. But at least you'll get down to the 5Kc drop that you wanted.
I'm very sorry that I can't help you anymore than this.
Jeff. |
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