MODULATION: Remove R131
AM POWER: VR10
SSB POWER: VR11
NOTE: Some radios have different colored wires on the clarifier control.
They are: YELLOW instead of ORANGE and RED instead of BLUE
If all goes well, you should slide about 4Khz down and 1Khz up.
WANT MORE SLIDE??
1. Remove D51 and put in a jumper.
2. Install a "super-diode" in place of the stock varactor D35.
3. Add a 4.7uh to 10uh choke to the banded-end of the stock varactor.
If you do the changes below you will get -6kHz to +6kHz with 0 right in the middle.
The Tx will track exactly with the Rx (confirmed on recently calibrated IFR1200S).
1. jumper R175
2. jumper D51
3. remove R149
4. remove R188
5. remove R44
6. remove the wire from the high side (+ or full cw pos) of the clarifier
7. connect pin 1 of IC4 to the high side of the clarifier
8. replace R174 with a 3k3 value
9. attach a 12k resistor from the jumper of D51 to pin3 of IC4
This is a little more involved than the other modification, but I believe it's worth the effort, it works like a champ!
NB: I've made one slight improvement to this Clarifier modification and that was the addition of a 7808 regular instead of the built-in regulator. The built in one isn't particularly stable when the radio has been boosted up.
This modification isn't for the faint of heart, but it's also pretty easy to do. It gives you the regular 40 channels, 41 through 80 and the third bank is 81 thru 100, 3a,7a,11a,15a,19a and 14 channels below channel one (limit of the PLL in this unit).
This mod uses an EPROM to contol the PLL, so access to an EPROM programmer is needed, plus it is recommended that only experienced techs attempt it.
Download the ZIP file for this Modification
Basically, you need to either add voltage or ground pin #16 on the MB8719 PLL.
Here's how to do a 10 Khz UP jump only:
1. Cut trace to pin #16 on the PLL.
2. Install a 4.7K resistor across the cut you made.
3. Using a SPST switch, one side of the switch goes to the cut-side of pin #16.
4. The other side of the switch goes to pin #9 of the PLL. (8 volts)
When you apply the 8 volts, this pulls pin #16 high causing the 10 kc jump up.
Note that this will not work on all channels.
For a 10 Khz DOWN jump only:
1. Ground pin #16 using a SPST switch. No cut to the PLL is necessary.
Pulling pin 16 low will cause it to jump down 10Kc.
This too will not work on all channels.
For a 10 Khz UP and DOWN switch:
Perform the trace cut/resistor addition described above.
Use a SPDT switch and wire as follows:
1. Center of switch goes to pin #9 of PLL (8 volts)
2. One side of switch goes to the cut side of pin #16.
3. The last side goes to pin #18 of PLL (or ground)
This will allow you to jump 10Kc up or down.
Or for the ultimate 10Khz jump mod, add binary adders onto the binary inputs of the PLL, this could also be settup and made to give you more band of channels !
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