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PLL02A 5khz shift mod question

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  #1  
Old 06-06-2009, 01:44 PM
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Default PLL02A 5khz shift mod question


hi i was wondering how to get the zeroes on my tristar 747(pll ic pll02ag). i found the pinouts here:PLL02A pin 4 FS is not hooked up on mine it says to pull it low. i tried that aswell as pulling it to 5volt high but no go. i dont like to pull the set off frequency with the clarifier mod. i know if it would work then i would have to move each of the six channel switch traces one pin over so my channels would work properly and then use the 10khz pin to move 5 khz. any ideas or have i missed something?
edit: its now not as simple as i had thought p8 is always high so i cant move it to p9. it looks like the only alternative is to align the set 2560khz lower in frequency which is too much engineering for me. i think my earlier confusion was that the frequencys dropped about 3 or 4 bands when the fs pin was pulled low (too much for the set?)

Last edited by fodendaf; 06-07-2009 at 12:55 PM.


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Old 06-07-2009, 03:36 PM
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Default Try this...

... apply 8-9 VDC to pull it "High" ... The Voltage to the PLL For Fn pins, etc. on the PLL02A is higher than most.

Also, remember that once you get this working, the 5KHz shift STARTS where channel "1" is on your frequency selector and shifts "up" 5 KHz per step. Let's take ch 38 for example. 27.385. When you flick your switch, you WILL NOT get 27.380 (or 27.390...) You'll get something like 27.130 (I did not take the time to calculate the exact value), because you're changing the OVERALL "divide by N" to 5 KHZ, NOT 10 KHz...

So, you may want to try the "00" trick this way:

http://buttfuzz.net/downloads/cb/pll...dification.pdf

If you have any more questions, feel free to ask, but I will tell you from personal experience this/these mods just aren't worth it on the cybernet chassis. Of course, your opinion, and mileage, may vary...

73,
Rob
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Old 06-08-2009, 08:57 AM
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thanks, the pdf mod seems a lot like plowboys 10 kc shifthttp://www.geocities.com/y40002000/plowboy2.html
i have heard that pulling the crystal off frequency is not a great idea and this is a sideband export set too so it has two extra crystals. i thought i could be done easily with the pll mod but unfortunately not. thanks anyway

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Old 06-26-2009, 01:53 PM
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Default buttfuzz, i might just take you up on your offer

would i be right in thinking if i put in another varactor diode off another scrap set instead of a cap as you suggest in parallel with the current varactor and run the other end to a pot and then to a 8-9 volt source then i would have a working (one way) slider that could get the shift i want (also is there a minimum capacitance that the extra varactor diode would have that would bring the set that bit off frequency) you see i think if i just run the pot to the existing varactor then maybe i would lose fm as the pot current would exceed the modulation current? i am thinking that way might be more stable as i would not have the long cable capacitance run problems to the 5khz switch.
i don't wish to be bothersome but i do miss the zeros on this set(i have it set up with a linear and i don't like messing with my 30watt ssb lincoln)
i was thinking of using a squelch and volume pot to replace my clarifier pot and then i could switch the second varactor on and off so as to be bang on frequency when i am not using the slider( although i could well have a problem in that the squelch pot may not be an electrically matched replacement for the clarifier, but it might not be a problem if i moved the knob or turned the pot)
i know i could unlock the clarifier and run the two varactor diodes in parallel instead of a super swing diode but then i would lose the locked clarifier which is important for dxing and the fm would be strange as is would modulate over a different frequency range?

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Old 07-26-2009, 08:45 AM
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Default 5 kHz shift mod for PLL02A radio

This mod is certainly possible with PLL02A based CB radios. I have done it with two radios: A HyGain 1 (model 2701) that I also had modified to 10 meters, and a Midland Export radio model 7001 that I left otherwise original. Both work great with this mod.
Firstly, it needs to be a radio where the MSB bit of the PLL chip (pin 7 on the chip) is made permanently LOW from the factory (pin is grounded), meaning the synthesizer's programmable divider range in stock condition is only used for half its range. All PLL02 based CB radios that I have seen in my life (and it was a LOT!) indeed have this condition, so you should be OK here.

What you need to do is two things: (1) Make pin 4 of the PLL chip LOW, meaning grounded (most radios do not have anything connected to this pin because the PLL02A has internal pull-up resistors, so nothing connected means the pin is HIGH)
Grounding pin 4 throws in an extra divide-by-two in the internal reference divider. The result is that the reference frequency on the internal phase detector will now be 5 kHz instead of 10 kHz. remember; the reference frequency on a PLL phase detector determines the ultimate step sizes the sysntesizer can make (which is now 5 kHz the way we want it)

However, you're not there yet. Now comes (2) that I promised you. The programmable divider coding also needs to be changed. Good news is that this is very simple. You need to shift the connections that go from the channel swith to the PLL chip all one pin lower, all of them. Remember from your schooldays (if you had them): Dividing (multiplying) by two in the digital domain is a logical shift right (left) for all bits.
So in practice this means that the switch wire that went to pin 15 (the LSB bit) now goes to pin 14; the one that used to go to pin 14 now goes to pin 13; the one that used to go to pin 13 now goes to pin 12 and so on.
Some of the MSB bits probably did not have switch wires going to them but were either tied permanently to logical 1 (5Volt) or logical 0 (0V) instead. You need to shift the logical state of those as well. For instance, if pin 9 was permanently ONE, pin 8 was ONE and pin 7 was ZERO, pin 9 now needs to become whatever pin 10 was (probably a switch wire); pin 8 will remain ONE (because pin 9 originally was), and pin 7 will now have to be made permanently ONE because pin 8 was.
Sounds complicated but it really isn't; it is basically a logical shift left (one position shift in the direction of decending pin numbers)

Now that you have done this, you will have pin 15 free (the LSB bit of the divider). You need to connect that one to a newly to install toggle switch (use the TONE HIGH-LOW switch if it was there) such that it either is open (then the internal pull-up ressitor will make the pin a ONE) or that it is grounded (making the pin ZERO)
The ZERO condition is the normal frequency for the channels (i.e. channel 19 will be 27.185 as before, and so on for every other channel)
Throwing the switch to the OPEN position will increase the division number for the synthesizer's programmable divider by one, and that will most likely result in the frequency going up 5 kHz (so 17.185 will become 27.190 MHz) . for some radios, the frequency might actually go down 5 kHz when flipping the switch, this depends on what mixing scheme is used in the synthesizer mixer (this is not the same for all radios)
Quite simple, don't you think?

Now comes the BAD news.
Not all PLL02A chips are the same. The PLL02A was originally based on the Motorola MC145109, which chip has the ability to throw in the extra divide by two in the reference divider when you ground pin 4. For some PLL02A chips, pin 4 is internally not connected. So your efforts will not pay off in that case.
The way to solve this is as follows: Solder out the chip, clean the pins, and put an IC socket on the board. In this way you can test different PLL02A chips until you find one that works.
Your solder skills are sub-par to do this? I will give you some solder tips.
First, get yourself a soldering iron with a fine tip (not too fine though, no SMT type) on which you can set the temperature. Most soldering goes wrong because people burn the PCB board with their solder irons, the types intended to repair the barn door. Don't use those big-uns.
Set the temperature for 300C (570F), not higher.
Then, get yourself a good solder sucker and solder wick, to remove the solder on the IC pins. Also, get yourself additional solder paste flux, rosin based (I use Kestler rosin paste flux formula SP-44)

Before you start desoldering, put rosin on EVERY IC pin, don't be skimpy, you can clean it up later. then, warm up the pin until the solder around it is FULLY melted and then suck the solder away with the piston based solder sucker in a single motion. Don't worry about overhearing things; with the tip set for only 300C AND the temperature distributing effects of the rosin you won't destroy the traces, nor the chip.
One other important thing: NEVER put mechanical stress on a PCB trace that is still hot. You WILL pull off the trace. So if some IC pins are still not free after your sucking action, use the solder wick to remove the last solder.do NOT put mechanical stress on the pins (by pushing or pulling) while the solder around it is not melted properly yet, you WILL pull of the trace.
If you work like this, you can solder on phenolic PCB boards (like most CB radios have) many times without any problem.
The excessive rosin cleans up nice using lacquer thinner and Q-tips. If , after clean-up, a nice shiny solder joint becomes visible, it is proof you did things right.
Good luck!

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Old 11-10-2009, 12:36 PM
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Thanks, colorburst you certainly know your stuff. I was put off the idea because I was rooting through http:\\malzev.tripod.com and I came across a truth table for the PLL02AG which is in my radio and the msb was high in the table but as you say it might be low in my box and theres only one way to find out. My radio was out of order for a good while cause I blew the 2sc1969 final driving a bv131 valve linear with no atu. I got it going again when I gutted a vhf two way radio and botched in a motorola tp2330(looks like the mrf455) and that end of it works well but i was measuring the final bias amperage as per the service manual and prodded the wrong final pin on the old 2sc1969 and let the magic smoke out. Now just am transmit modulation gets intermittently muffled and garbled and what few techies are near me don't like to work on a radio someone else has been messing with. problems, problems.

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