Replace MB8719 with MC145106

[StaplerUk]

I have a PC879 148 with damaged MB8719 and only place i can source these are from the US and are a little over my budget, Can an MC145106 be used and if so how ?

I did a search but no results.

I know the MC145106 can replace the PLLO2A easy enough and have done this a few times, But can the same be done with the MB8719.

I have plenty of 145106'S pulled from old muppet sets DNT/ICOM 1050/LCL2740 etc so have room for errors.

Thanks for any info

Regards

[The Defpom]

I believe (although I have never tried) that you cannot replace an MB8719 with a MC145106, as they have a different PD output, one is reversed from the other.

You can replace the MB8719 with an RCI8719-99, which can be obtained from various places online.

[lbcomms]

Hi,
You can replace the 8719 with a '151, although you will have to make a new filter circuit for the PD output:
That's easy though...
- Connect the PD pin to the tuning voltage on the VCO via a 3k3 resistor
- Connect the IC side of the resistor to ground via a 0.1uF tantalum capacitor
- Connect the VCO side of the resistor to ground via a 0.22uF tantalum capacitor
- Connect the VCO side of the resistor to ground via a 10uF electrolytic capacitor in series with a 680 ohm resistor

EDIT: The MC145106 is a "cut down" version of the '151, so you should be able to use it. The '106 is used on several (Uniden made) marine radios and UHF sets here in Oz.

I can't supply a circuit, but I did do this mod years ago (early 90's!) to a Uniden Grant to get it on 10 metres, way back in my uni days.
I still have that radio, and it still works

The "Direction" of the PD comes from the VCO design, not the PLL IC - the '8719 chassis VCO control voltage rises with frequency, therefore we can tell that the control voltage connects to the cathode of the varicap. Other sets, like the cybernet SSB, "reverse" their direction twice due to the VCO design (control V to anode / downmix uses both hetrodynes) so a standard PLL like the PLL02A can be used. More advanced PLL ICs like the MC145170 let you do a "reversal" in software, making circuit design easier (control V to anode or downmix using both hetrodynes could be used)

You will probably need an EPROM and a level translator IC like a ULN2003 (the '151 has a VCC of 8 or 9 volts, EPROMs can have 5V max) to get the channels to read correctly.

The '106 in a UHF set I have on the bench now (Electrophone TX470T) rises the tuning voltage with frequency, so you should be OK.

Personally, I'd be using a 145170, but you will need to code a PIC or similar for it as the '170 is serial input. A lot less work to put together (about a quarter of the soldering and wiring), and you could do other neat tricks like scanning, instant call channel button, etc, etc.

Hope this helps,
Sue

[zodiac]

Nick,
I have a couple of PLL's for the MK1 148 second hand, if you want one PM me with your Email address and we'll sort you one out.
Dave.

[oldhaq]

I've changed out an mb8719 for an mc145106 a few times over the years.
I leave the 8719 nearby and use pins 1-4 to filter the PD from 145106.
Mod done mainly to give an exact 5kc jump using pin 17, by tying pin 6 to ground (FS=5 Khz steps) and shifting the PLL control lines from the channel switch along/up a pin on the PLL.
You could of course use FS=1 to stay with 10kc steps.

This is one of my favorite mods.

You will also double the available N-codes using this method, or x4 using 10kc steps.

Same principle applies when doing this on an 02a radio.

Sorry Stapler, this probably doesn't help you if you've completely blown your 8719, perhaps try to pick up a discarded MB8734 cheap/free from someone here.