The uncommon Pin 17 on the MB8719 PLL modification .. safe.. or not?

[@dj56cbsales]

Mark Do you have any info on the pll board to replace the 8719. What channels does it give. I have been looking for this for a long time. thanks

[@TheDefpom]

I just picked up a 148 parts radio from eBay, have been fiddling around with this myself today. I've known about the mod for a while but never tried it. I will be uploading a video shortly with my findings and my theory of how this works. I am planning on modding the radio for two bands using the 145106 (because I want the 5KHz offset) and an arduino controller, but I'm thinking to myself why I am recreating something you have already done with your mod board?

[@mikesradiorepair]

As I told you I have seen it done but have never done it myself.

[@TheMechanic241]

You are going about it all wrong... Pin 17 should never connect to Vcc directly or through any resistor, choke, inductor or anything else. The entire trick is, applying Half Vcc to Pin 10. Pin 10, on most radios with an MB8719, is isolated "left unconnected", except for radios like the Teaberry Stalker IX (Radio's like the Teaberry Stalker IX have an 11.1125mhz crystal and pin 10 is tied directly to ground so there is no need to swap crystals in these radios, just free pin 10 from ground and do the rest). Pin 17 is half of Vcc that Pin 9 supplies. This is why tying Pin 10 to ground through a 4.7 k resistor, then switching in and out Vcc or Half Vcc to Pin 17 splits the coding. If you use an 11.1125mhz Crystal instead of the 11.3258mhz crystal, you would get a more central spread of channels, both upper and lower, or leaving the 11.3258mhz crystal will get you more into 10 meters... Don't stop there! One of the reasons most folks can't get the modification to work, is the fact that the VCO unlocks. There is a simple mod for that too... It relies on clipping or removing a resistor in the VCO Circuit. Typically R95 on the 2000 or 148 GTL, R71 on the Stalker IX. There is a Yahoo! Group called "The Mod" in which you can find a PDF Document I created years ago, explaining everything you need to get 192 channels from an MB8719 PLL. The document is called "_Poormans 192 Mod - Rev.1.02.pdf". I would have posted a direct link from my website from years ago, but noticed it has been erased and linking the PDF in the group does not work...

[@DesertOasis2023]

Yeah, the way the video is explaining it is confusing. Pin 10 to ground, pin 10 to +8 or pin10 to +4 (half vcc) using a three position switch gives hi/mid/low using a 11.1125mhz crystal. Apparently the guy doesn't get that pin 10 has 3 functions unlike the rest of the binary inputs 11 - 16

[@matthewdavies2057]

Everybody and their uncle has played with those pins. I did it in 1983 and all I ever got was a 3rd "funny channel" switch of very limited use. 17 didn't react like a BCD selection pin so I, and all the others, ignored it. Welcome brother!

[@DAVIDGREGORYKERR]

Mark19960 it's David here maybe they are wanting to have more channels or something if so then it should be replacing the PLL with the MC145151 or a board using discrete programmable divider chips and Phase Comparator chip plus the oscillator to make it work and give the user more channels.

[@DollarbillDollarbill]

Back in the 90s ever radio had this MOD. Much better to order temputure control oscilaters.crystal swapping on channel 9 switch. Clarifer would get tied to transmit and then line radio up. .Replaced many back to stock. Still got a bunch. Work fine as long as you don't go jumping. Yes jumping work for many butchers as long as you keep radio out of cold and hot places and didn't destroy your modulation[which everyone was doing].Became a ham radio operator and have not even thought about this MOD in years. Nothing wrong with cb. Just be respectful. Same for hams.