This is the most commonly used chip on the market today so I will try to make this as Simple as possible! the following is a Diagram of the MB8719 Chip Used in all the New radios! ÚÂÄÄ¿ ÚÄÄÄ¿ 2nd amp o ³o ÀÄÙ o³ Grnd - vss 2nd amp in ³o M o³ F in pin4 out ³o B o³ P0 inv up amp ³o 8 o³ P1 PD output ³o 7 o³ P2 lock det. ³o 1 o³ P3 ref{Q-out ³o 9 o³ P4 ref{Q-in ³o o³ P5 VDD - 9v ³o o³ divide/inverter ÀÄÄÄÄÄÄÄÄÄÙ on input P6 Because of Pin 10, the chip downmixer can be referenced to two different frequencies with the same 40 channel result! In radios using the 11.11258 crystal, Pin 10 is Grounded causing the Chip to go to full up-count. In this case lifting Pin 10 from Ground will cause the radio to cover 120 channels with the highest frequency being 27.445 MHz. The other chassis that have pin 10 high, use a 11.3258 MHz. crystal for reference. In these Chassis, by grounding pin 10 the Radio goes up in frequency by a similar range. The truth table is based on the 11.3258 MHz. crystal reference. CLARIFIER: Because of the various versions of the 8719 Chassis i will Use the President Mckinely as a Example. this conversion is for all 8719 Chassis. The following covers all President , Most Cobras , SBE, Stalker, Realistic and other radios with a Uniden Chassis. 1. Cut out D-36. 2. Remove R-187. this applies voltage to the circuit in the transmit and will cause tracking problems if not removed. 3. Leave the center wire from the Clarifier alone! 4. Follow the orange wire from the clarifier control and remove it from where it connects to the radio. (this point will vary with different radios.) 5. Connect this wire a (longer length may be added) to pin 3 of IC-5. (located bottom of board on left side with the radio facing front.) This supplies constant 8 volts from the Regulator. 6. Follow the red wire from the clarifier control to the point where it is connected to the chassis. 7. Connect this wire to ground through a 47 ohm resistor in series with the wire or through a 1N914 signal Diode with cathode to ground. this is important because it isolates the regulated supply from the ground. In Case of Regulator failure the diode or resistor will act as a Fuse to protect things. this gimmick can save you a lot of problems and grief so use it! 8. Slide can be increased by lifting the Anode of the Varactor diode and add a Series 5.6 - 8 uh choke to Ground. if more slide is needed either purchase a Super varactor or go to your local TV Shop and Scrap one from a Vhf Tuner! THIS DIAGRAM COVERS NEARLY ALL UNIDEN CHASSIS WITH THE 8719 ÚÄ¿ ³ ³³-47 ohm added ÚÅ¿À´ to grnd. ÀÄÄ¿ À¿ Clarifier> o o <ÄÄÄÄÄÂÄÄÄÅÄÄ>ÄÄ¿ ÚÄÄÄÄÄÄÄÄ> o ³ Å ³ ÚÁ¿ ³³ D36 apply constant ³ ³ ÃÙ 8 volt source at ÀÂÙ ³ this pin. o<Ä¿ o<Ä¿ ³ ³ remove this resistor and diode (D36 & R187) TECH NOTE: In some Washingtons and Robyns as well I have found pin 10 was wire-wrapped under the chip to ground. Suppliers of Conversion kits tell you you have to replace the chip! This is false! Carefully heat the pin and push the ground wire off the pin. cut the wire as close as possible to the chip and proceed with the Conversion! (Another first from HCS)! 1. replace the removed Crystal with a 11.3258 MHz. Crystal NOTE: if you use a Uniden Stock crystal (11.3258) which is cut to a higher PF. load than the Special Conversion Crystals you may have a Difficult time to recenter the Clarifier! Be Aware 2. Switch Method 1 will start up coverage from 27.605 and go to 28.045 3. Switch method 2 will give normal operation in the center postion 2 - 27.455 - 27-605 and in position 3 will give from 27.605 - 28.045. This switch is intended for amateur use when converting the radio to 10 Meter operation. SWITCH 1 ÚÄÄÄÄÄÄÄÄÄ> to Chip VCC+ Supply ÚÅÄÄÄÄÄÄ¿ ÚÄÄÄÄijo o³ ÚÁ¿ ³ ³ 1N914 ÃÄ´ ³o Úo³ ÀÂÙ ÚÄÄÅÄÄÄÄÄÙ ³ ÀÄÄÙ ³o o³ÄÄÄÄ> To Pin 12 at after resistor ÀÄÄÄÄÄÄÄÙ is has been added Switch can be SPST or DPDT SWITCH 2 ÚÄÄÄÄ> to pin 10 ÚÄÄÄÄÄÅÄÄ¿ ÚÄÄÄÄÄijo ³ o³ÄÄ¿ ³ ³ ³ ³ ÚÁ¿ ³ ÚÄijo ÀÄo³ ³ ³ ³ ³ ³ ³ ÀÂÙ ³ ³ ³o o³ÄÄÁÄÄÄÄ> To Board Ground ³ ³ ÀÄÄÄÄÄÄÄÄÙ ³ ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ> to pin 11 ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ> to pin 12 MB8719 Coverage from Channel 45 - 99+ with one switch & diode Protect. 10 METER CONVERSION: Replace Crystal with 11.8391 MHz. Covers Phone band Above 29.5 MHz. Using a 11.660 crystal for 28.0 to above 29.0 MHz. MB8719 Tuneup: Connect a Freq. Counter to TP1 Put the Radio on Channel 20 In the USB mode adjust CT3 for 35.0075 MHz. In radios with choke added to Clarifier set control at 3:00 clock position. Switch to LSB mode and adjust L19 for a Freq. of 35.0025 Switch to AM Mode and adjust L20 for 35.0050 MHz. Peak Transmitter by tuning L26, L27, L29, & L36 AM Power is adjusted for VR-6 SSB ALC is adjusted with VR-7 To Increase Modulation Cut the collector of TR-32 Touch up Recieve stages if converting to 10 Meters SUPER TRICK: If you Need More bandwidth connect a Varactor to the coil side of the cut trace and the cathode of the VCO Chip side. Retune the VCO coil for operation over the entire range! Cut The trace from the VCO coil going to pin 6 of the VCO And Do the conversion described Above. All users who register there Copies of These conversions will recieve for $5.00 complete Written Documents and Complete Drawings with much more Information and tricks and More Updates on the Export radios & Conversions for FM and Much More. if you Use my Conversions Please send a Donation of not Less Than $10.00 Check or Money order to: Carl D. Henson 315 Summit Ave. Springfield, Il. 62704 (217) 523-0252 These Conversions cannot be Reproduced in any form of Media without my Written Consent! This is shareware not Public Domain! No Software Vendors are allowed to Copy or Distribute my Products unless a Prior aggreement is arranged by Myself! This is Copyrighted materials any and all Violators will be Prosecuted By The Law! This is Being Distributed for HCS INC. By Carl D. Henson. Copyright (C) 1990-1991 Carl D. Henson