5KC/half channel mod for mb8719 or pll mc145106 info needed

[Techno1]

Has anyone tried or have directions for the pll 8719 or the pll mc145106 for a 5kc jump on the channels like half channels.
Not interested in doing the clarifier expansion its already unlocked and just want to do it with the pll if possible.
Been looking but not much info for a easy mod (maybe cant be done>LOL) i have the 10kc mod but need the 5kc mod
thanks

 

[nomadradio]

The only 5 kHz mod for the 8719 will be in the clarifier circuit.

The 8719 PLL can't be configured for 5 kHz steps. The MC145106 can, but this changes the math feeding the chip's binary inputs.

The, er "simple" way for that chip is to change pin 6 from high to low, take the six wires from the channel selector loose from pins 17-11 and "move" them all down one pin number leaving pin 17 loose. Same goes for pins 8,9 and 10. The channel selector will now tune the same forty 10 kHz steps, and a toggle switch on pin 17 selects 0 or 5 kHz for your last digit.

Since the frequency we're filtering from the varactor's DC tuning voltage is now 5 kHz rather than 10 kHz, some fine tuning of the tuning-voltage filter may be necessary. The Jurassic "Redco Digiscan UFO" external controller tuned that chip in 5 kHz steps. They used a trimpot in series with a 10uf cap placed across the radio's VCO tuning voltage. The idea was that the trimpot would let you "null" the 5 kHz ripple from the VCO voltage. Mostly worked.

73

 

[Techno1]

nomadradio

thanks for the info I did read that out on the net but thought I might ask if there was an easier way with the MC145106.
I guess I will leave it alone and stay with the 10kc mod.
Doing the clarifier makes it too sensitive.
On the current clarifier mod it goes down about 4 and up about 2.5 and too sensitive.

Again thanks for the info