Hardware Hacking

To expand coverage to 141.0 - 150.995mhz.

Cut D34 on control unit, and then reset the microprocessor.

CROSS BAND REPEATER MOD
To operate the TS790A in the repeater cross band mode,diode D32 on the
control board must be opened.In addition,two resistors must be soldered
to a 13 pin din plug which will be connected to the ACC. 2 jack on the
back panel of the transceiver.

TO LOCATE AND OPEN D32
1 Disconnect the power supply and antenna from the radio.

2 Remove the 14 screws that secure the top and bottom covers.

3 Carefully remove the top and bottom covers.

4 Locate the control board. this is a vertically mounted board that is
positioned approximately 1 inch behind the front panel.

5 Locate diode d32 towards the top right side of the board.

6 Using a small pair of wire cutters,cut the lead of the diode. do not
pull on the lead or the diode as this may tear the foil on the other
side of the board.

7 assemble the radio by reversing steps 1-3.

13 PIN DIN PLUG CONFIGURATION.

1 Using a small flat blade screwdriver,lift up on the tab of the nylon
cover.

2 Once the tab clears the slot of the metal holder,pull the cover
off the plug.

3 Carefully separate the two metal holders and remove the pin assembly.

4 First tin pins 1,8 and 11 of the assembly so the resistors can easily
be soldered in place.

5 SOLDER A 100K ohm,1/4 watt resistor between pins 1 and 11 of the
assembly (the resistor leads should be cut and shaped before soldering).

6 Solder a 1.5K ohm,1/4 watt resistor between pin 8 and the lead of the
100K ohm resistor that is attached to pin 11.(the resistor leads
should be cut and shaped before soldering)

7 Wrap a small piece of electrical tape around the resistors.This will
insulate them from the metal holder after the plug is assembled.

8 Mount the pin assembly in the two metal holders.

9 Slide the cover over the plug until the tab engages in the slot.
The “U” shaped strain relief will not be used.

10 Plug the 13 pin din plug in the ACC2 jack on the back panel of the
radio.

OPERATING PROCEDURES

The repeater cross band operation allows the TS790A to receive on one
band and re-transmit the signal on the other band. Incoming signals
will automatically be switched to the sub band.The TS790A will then
re-transmit the signals from the main band. Each band may contain
offset and sub-audible tone information (an optional TSU-5 must be
installed in EACH BAND for decode).

1 Press the MAIN function swich to select the MAIN band.

2 Select the first operating frequency and mode (fm only).Select the
offset as required.

3 If the CH.Q is on,press the CH.Q switch to turn the function off.

4 Select the sub-audible tone as required .

5 Transfer the contents of the MAIN band to the SUB band.

6 Select the second operating frequency anf mode (FM ONLY) and turn
the CH.Q off.

7 Select the offset and sub-audible tone as required.

8 Adjust the MAIN and SUB band squelch controls to the threshold
point.The TS790A will transmit in the repeater crossband mode if
the squelch controls are set too low or a signal is received.

9 Adjust the power control to allow normal output power from the MAIN
band.

10 Adjust the sub band volume control to a normal listening level to
monitor incoming signals.

11 To place the radio in the repeater cross-band mode,press the F.
switch and then press the M.IN switch. An asterisk will light in the
MAIN band display for confirmation.

12 To cancel the operation,repeat step 11 and disconnect the DIN plug.

13. If the DIN plug is left in place after use,bleedover from the SUB
band audio if present will be mixed with any transmitted audio.
This will make your audio during a conversation hard to understand.

TSU-5 TONE UNIT

When the TSU-5 tone units are not installed,only the tone (encode)
function can be used.
If CTCSS is to be used it must be installed in both bands to function
with the cross-band repeater mode.

TX AUDIO ADJUSTMENT

The audio gain can be adjusted by variable resistor VR36 on the IF unit.
If the range of VR36 does not suffice for normal transmit audio,the
values of the resistors on the 13 pin din plug can be changed.
as an example,if the audio is too low,reduce the value of the 100K ohm
resistor and increase the value of the 1.5K ohm resistor.

TO ACCESS VR36

1 Remove the bottom cover of the radio to expose the IF unit.

2 locate VR36

3 Use a plastic alignment tool to adjust VR36 for normal TX audio.

4 After the audio is adjusted,install the bottom cover.

1. No output TX: SG switch is “OFF”.

2. No TX, RX or VFO: There is no 9 Pin plug installed.

3. Low RX Sensitivity, no TX: The transverter switch is”ON.”

4. S Meter full deflection when first turned on: Makesure RF gain is
not fully CCW.

5. If digital display does not count: Make sure DH is not”ON.”

6. If there is no DG display: Make sure you are not inREMOTE VFO with
no remote VFO attached.

7. When intermittant in any circuit:

a. Check for loose black jumper from point to pointon circuit
board.
b. Check for broken foil path.
c. Check for component that has been pulled out or
loosely soldered.
d. Check for solder splash across foil path.
e. Check for loose pins.
f. Check for component leads touching to metal IF
cans.
g. Check for wire not soldered at function switch orat any switch
or control.
h. When checking FET’s, check for excessive voltageat can top
usually source, or same G-1, G-2 voltage.
i. Check for loose Molex mini connector or any foreign substance on
pins.

8. Complaint of frequency shift when TX-CW: This is
normal. 800 Hz.

9. Not proper PLL action: Make sure PLL slide switch isin NOR not
TUNE.

10. Receiver audio self oscillation at high level: Make sure audio
board mounting screws are tight.

RECEIVER

1. Low audio output receiver sensitivity and no transmit: -6v supply is
bad. Q13 on FIX VOX unit.

2. 25 kHz calibrator will not zero: Add 3 pf in parallel with TC-1 on
the marker unit.

3. Receiver sensitivity down: Q2 on RF unit. +9v on PD unit is shorted.
L-6 shorted to ground.

4. Intermittant receive when moving set.: Check for touching terminals
at final relay socket.

5. No receiver or digital: 14v wire pinched between DG-1 chassis and
ground.

6. Receiver sensitivity 40 db down: Check for shorted L8, 1.8 MHz
antenna coil on coil pack.

7. Adjacent signal interferance: See TKC bulletin.

8. No receive audio: Check for shorted TA-7201P module at X49-1080-00.

9. Poor receive audio: The 100 V AC 120 V taps were miswired.

10. Receiver doesnt work 20-40: Check for wafer touch to ground on band
switch.

11. No DG1, no RX, no TX, no VCO: Bad D1 5 volt zener on relay unit.

12. RIT action seems warbly: See TKC bulletin.

13. Receiver has bad static and is noisy: Bad C14, C15, tantalum on PD
unit.

14. VFO frequency shift: Check for loose tension of VFO tension
spring.

15. USB/LSB will not work: Check for loose connection at C18 CAR-1 unit.

16. Intermittant audio: Check for loose mounting screws on audio board.

TRANSMITTER

1. Mushy audio on transmit: Mic amps Q20 and Q21 on IF unit are bad.

2. No 14V supply: Bad bridge diodes D8-D10 on X43-1090- 02.

3. Intermittant operation of any one band: Check for loosely soldered
Xtals in PD unit.

4. Mic gain down: Cold solder joint at SSB xtal filter IF unit.

5. Self oscillation when TX: Bad final tubes. Burned cathode resistors
10 ohms R2, R3 at final unit.

6. No VOX operation. No sidetone: Burned resistor R12 220 ohms at key
socket.

7. No USB or LSB: Check CAR1 X1-X2 crystal for cold solder joint on CAR-
1 unit.

8. No TX: Check for shorted Q1 and Q8 balanced mixer on RF Unit.

9. No ALC meter movement: Readjustment of meter amp VR1, VR2 on IF unit.

10. Intermittant ALC action after peaking drive: One final tube is bad.

11. Fix lite on when in VFO position: Wire shorted terminals on function
switch.

12. No loading of TX: Cold solder joint at relay socket RL1 antenna
relay.

13. Using Sure 444 speech processor is distorted: See TKC bulletin
regarding 16db pad for mic input.

14. No relay closure on TX: Q9 on fix Vox unit is bad.

15. Very low RF output only when using RF speech processor: Bad Q30 on IF
unit.

16. Low RF output on SSB without RF speech processor: Bad Q20 on X48-
1150-00.

17. Large audio difference between USb and LSB: realign carrier unit per
TKC specifications.

18. No loading on 40 meters: Foil path is open on RF coil pack.

19. No tX when using send switch: Bad R28 1K and Q9 on FIX VOX unit.

20. Blows fuse: Check for shorted C21, C22 100uf 500v.

21. No drive, no TX or bias: Open screen resistor R6 470 ohm at rectfier
unit.

22. VFO intermittant: Check for cold solder at VFO power plug.

23. Audio distortion on TX with processor: C96 may be loose on IF board.

24. Faulty LED indications: Check for loose ground screws on LED board.

25. Low output on CW: R14 470 Ohm touch to filter case on IF unit.

26. VOX operation is intermittant: Solder touch VS terminal oand 14v at
X50-11350-00).

27. Intermittant TX: Make sure ground strap for 12BY7 shield is under the shie
ld.

28. Insufficient power out to drive linear amplifier: An increase of 5-7 watts
can

29. VFO output level is down: Q2 inside VFO is bad.

30. No TX or RX on any band. No VCO output: Q14 on X50-1330-00 is bad.

31. No TX or RX: Loose contact VFO output terminal on Fix Vox unit.

(c) 102577TKC
Copyrighted Kenwood U.S.A. Corp.
Relayed by KD2EJ with permission from Kenwood U.S.A.
————————————————————————
Note: I haven’t tried or verified this, proceed at your own risk. WA2ISE

From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: rec.radio.amateur.misc
Subject: TS820 speech processor allignment procedure
Keywords: ts820
Message-ID: <1991Dec1.030349.25950@cbfsb.att.com>
Date: 1 Dec 91 03:03:49 GMT
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 53

copied from packet, from kd2ej:
SB-009

TS-820 Speech Processor Alignment 11-17-76

The following alignment procedure may be used in lieu of the one in the
Service Manual.

Test Equipment required:
Audio Signal Generator
Audio VTVM
Oscilloscope or RF VTVM

1.Preliminary control settings:
Screen grid switch off.
Mode switch to USB.
Comp Level to USB.
Processor SW to Pull “ON”.
Meter switch ot “Comp”.

Send/Rec switch to “Send” as required when making adjustments.

2.Apply 1500 Hz audio signal to the mic jack at 10mv level.
Connect RF VTVM or scope to TP-2.
Adjust T-11, 12, 13, for maximum level on the S-meter.
Adjust T-14 for maximum level on scope or VTVM at TP-2.

3.Turn compression level to min, (CCW).
(Reduce audio sig at mic jack to 0.3 mv.
Adjust TC-4 (Freq response for speech processor) so that level at
TP-2 is not changed when changing audio gen from 400 Hz to
2000Hz.

4.Turn compression level to max, (CW)
Set audio gen to 1500Hz at 0.3 mv.
Adjust TC-3 and VR-6 (carrier bal for speech proc) for maximum level
at TP-2.

5.Set audio gen to 10 mv at 1500Hz
Send/Rec switch to send
Adjust VR-7 (comp level for speech processor) so that the level at
TP-2 is not changed when turning the processor on and off. VR-7
should be adjusted for the particular microphone the customer
will be using with his TS-820.

6.Finally check for non distortion of signal, and that comp level of
20db can be obtained at full comp on.

ALL BAND TRANSMIT
—————–
Kenwood markets this radio worldwide, and has made provisions
to allow the radio to transmit between 1.625 mhz and 29.999 mhz.
I am providing this modification for INFORMATIONAL PURPOSES ONLY!
DO NOT TRANSMIT OUT OF BAND, THIS WILL JEAPORDIZE YOUR LICENSE,
AND HAVE THE FCC, AND/OR INTERNATIONAL AUTHORITIES KNOCKING AT
YOUR DOOR!!!

The All-band transmit modification requires the removal and re-
location of a diode on the the digital board which is located
behind the front panel. The US version of the radio has diode
D11 installed, and diode D9 removed. D11 must be removed, and
installed in the D9 position. This modification IS NOT for the
faint of heart, as it entails removing the front panel, and the
digital board. Note that the digital board has solder holes that
are through-soldered; that is, there are circuit traces on both
sides of the board, so make sure that ALL solder is removed from
the holes. This modification will also allow the antenna tuner
to tune anywhere the receiver is tuned. This modification should
ONLY be performed by those familiar with soldering and de-soldering
techniques, and requires patience, and dexterity.

. Broadcast Band Sensitivity
————————–
BCB sensitivity REALLY suffers as a 24db attenuator is inserted
when band-switched. This attenuator circuit is very similiar to
the TS-430/440. Possible modification?

. Additional Front Panel Functions
——————————–
Pressing SCAN + TX-M.CH will set the radio into its extended
function mode. These options can be scrolled via the M.CH/VFO CH.
switch. The following are the extended functions:

00 - This is the ROM Checksum displayed as a 4-digit hexadecimal
number This cannot be changed.

01 - Allow filter selection in transmit. Initially set OFF.

02 - Antenna tuner power down. Initially set to OFF.

03 - Antenna tuner non-stop mode. When set to on, the antenna
tuner will not stop when the lowest VSWR is found. Initially
set to OFF.

04 - Store mode, and filter settings prior to changing bands, or
channels. Initially set to ON.

05 - Display -HELLO- on digitial display, and send it in Morse
code on power up. Initially set OFF.

06 - Turn full LCD display ON on power on. Initially set OFF.

07 - Turn Subtone ON or OFF. Initially set ON. Note that even
when set off, the TONE indicator will be lit on the display.

08 - Unknown. Initially set OFF.

RF Board Controls
—————–
VR - RX BAL
VR - TX BIAS
VR - TX BAL
VR - TYP (50W output power adjust, used with S1 below)
VR - MIN (?????) / internal antenna tuner
VR - TUN (Tune mode power adjust)
VR - VSF (THIS IS THE 100W POWER OUTPUT CONTROL)
VR - SWR Protect activation
VR - PWM (Forward power meter calibration)
VR1 - RWM (Reflected power meter calibration)
VR1 - AL0 (ALC meter zero)
VR1 - ALM (ALC meter calibration)
VR1 - CPM (Processor meter calibration)
VR1 - ALG (ALC gain adjustment)

S - All Band Power Down Switch (Decreases power to 50 watts)

IF Board Controls
—————–
VR -
VR -
VR -
VR - Beep volume
VR - Sidetone volume
VR - Processor adjust
VR - ?????
VR8 & VR9 - ?????
VR1 - ?????
VR1 -
VR12 & VR13 - S Meter adjust
VR14 & VR15 - AGC adjust
VR1 - Notch filter adjust

. PLEASE NOTE!
Most of these controls are 1/8″ pots, so if you intend to adjust
them use a VERY SMALL non-metallic tool.