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