Modifications for the
Kenwood TR-8400
Hallo !
Ich habe hier noch die Anleitung wie man den Kenwood
TR-8400 (altes PLL-Rastermonster) auf 9k6 Umbaut. Dabei
ist noch eine Modifikation wie man die Umschaltung auf
senden verbessern (verschnellern) kann.
Hier nun die Modifikationen:
Das tuning des TXDelays hab ich ausprobiert, leider hatte
ich keinen 390 Ohm Widerstand zur Hand, mit 470 Ohm kommt
man auf 160mS Umschaltzeit.
Obs noch schneller geht probier ich nochmal aus wenn ich
die notwendige Modifikation für 9k6 vorgenommen habe,
mangels Modem hab ich das noch nicht in angriff genommen.
Dann kann ich auch was über Tauglichkeit usw. berichten.
73s Holger dg6dbf @ dk0mwx
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de DL1YDD @ DB0IZ
TR-8400 Transmit Delay Time
PLL lockup time when switching from receive to transmit
may be shortened for faster transmitter response. This
change applies to units before serial number 1060455.
On the PLL unit X50-1670-xx, check the values of R31 (390
ohm) and C47, C48 (6.8uf) near Q7 and Q8. If these
component values differ, change as required. This will
give approximately a 0.12 second delay, which should be
satisfactory for practical use. However, if shorter delay
is required, replace R31 with an 820 ohm resistor. This
will yield an approximate 0.096 second turn-on delay.
No adjustment is required after this part change.
Note: When R31 is 820 ohms, CTCSS (Subtone) will be
slightly distorted.
Installation time for this procedure is 1/2 or less.
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de DL1ZAX @ DB0EAM
Hallo 9600 Baud User
Da ich auf meine Anfrage "Umbau Kenwood TR-8400 auf
9600 Baud" keine Antwort bekommen habe, blieb mir
nichts anderes uebrig es selber zu versuchen. Dank der
Hilfe von DB8AS und DG9FU war das dann auch gar nicht so
schwer.
Das RX-Signal kann man auf der Platine "RX.TX
UNIT(X44-1340-61)" an der Diode D7, nach der Spule
L10 abgreiffen.
Diese Platine ist auf der Unterseite von dem Geraet, also
da wo der Lautsprecher ist.
Die Diode ist links neben der Stelle wo der Lautsprecher
bei geschlossenem Deckel sitzt (Bedienelemente zeigen zu
Ihnen).
An D8 kann man die Abschirmung des Verbindungskabels zum
G3RUH Modem anschliessen, sie liegt auf Masse.
Das TX-Signal wird ueber ein Relais der Diode D1 zu
gefuehrt.
Diese Diode befindet sich auf der Platine "PLL
UNIT(X50-1670-61)" unter dem Blech, hinten links auf
der Oberseite des Geraetes.
Das TX-Signal vom G3RUH-Modem muss ueber ein Relais
angeschlossen werden welches von der PTT des TNC2
geschaltet wird.
Bei Empfang darf das TX-Signal nicht an der Diode anliegen.
Dazu habe ich das PTT Signal ueber den freien Pin von der
Mikrofonbuchse zum Relais im innern des Geraetes gefuehrt.
Das Relais hat zwei Kontakte, ueber den einen wird das
PR-Signal geschaltet und ueber den anderen Kontakt wird
die PTT vom TR-8400 geschaltet.
Dadurch kann man das Geraet auch nach dem Umbau mit einem
Mikrofon betreiben ohne das es zu problemem kommt.
Dieser Umbau arbeitet ohne Probleme.
Fals noch fragen sind, nur mut...
vy 73 de DL1ZAX Dietmar @ DB0EAM
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TR-8400 Transmit
Delay Time |
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PLL lockup time when switching from receive to transmit
may be shortened for faster transmitter response. This
change applies to units before serial number 1060455.
On the PLL unit X50-1670-xx, check the values of R31
(390 ohm) and C47, C48 (6.8uf) near Q7 and Q8. If these
component values differ, change as required. This will
give approximately a 0.12 second delay, which should be
satisfactory for practical use. However, if shorter delay
is required, replace R31 with an 820 ohm resistor. This
will yield an approximate 0.096 second turn-on delay.
No adjustment is required after this part change.
Note: When R31 is 820 ohms, CTCSS (Subtone) will
be slightly distorted.
Installation time for this procedure is 1/2 or less.
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TR-8400 Transmitter
Freq Response, Voice or DTMF |
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Operator complaints of insufficient lows in transmit,
or faulty Autopatch operation traceable to incorrect twist
(high to low tone group balance) may be remedied by
changing two capacitors at the mic amplifier input.
On the RX/TX unit X44-1340-11, change C62 and C65 from
0.1uf to 1.0uf, 35v tantalum (CS15E1V010M) to increase low
frequency transmitter frequency response. Adjust Deviation
(VR3) or mic gain (VR2) as necessary.
Installation time for this procedure is 1/2 or less.
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TR-8400 Sub-audible
Encode Installation |
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When installing a sub-audible encode in a first-lot
radio, change the Tone switch power source from the 8C
(common) to the 9T (transmit) line. This will prevent the
encoder from distorting the receiver when the Tone switch
is ON.
Procedure.
- Remove the bottom cover (2 long screws, rear, 3
short screws, front) and unplug the speaker.
- Cut the GRAY lead to the Tone switch wiper one inch
from the switch. Tape-insulate the long lead to the
harness.
- Connect the switch wiper to the Mic connector, pin
5.
(See Fig. 1)
- Install the encoder, connect the speaker, and
replace the bottom cover.
For complaints of distorted sub-audible tone in a
first-lot unit, replacing components and readjusting the
PLL will reduce or eliminate distortion.
Procedure.
- Remove the top cover (4 screws).
- Remove the rubber conductive shield.
- remove the aluminum cover from the PLL unit
X50-1670-xx (17 screws).
- Unplug connectors J2-J6.
- Remove 11 screws and 2 threaded studs securing the
PLL printed circuit board. Shift the board to the
rear, then swing up and tothe right.
- Use Wikit or a desoldering tool to remove and
replace:
Component was replace width (vicinity of Q7)
R30 12 Kohm 18Kohm 1/4W
R31 820 ohm 390 ohm 1/4W
C47 6.8uF 15uF Tantalum (observe polarity)
c48 6.8uF 15uF Tantalum (observe polarity)
Note: Don't create solder-bridges or lift the foil.
- Reverse steps 5, 4, 3 to partially reassemble.
- Perform the PLL adjustment listed in the Service
Manual, page 24, item 2.
- Reverse steps 2 & 1 for final assembly.
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TR-8400 RX internal
sporious signals |
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Receiver internal spurious signals
occurring at xx1.7
MHz and xx6.7 MHz may be reduced or eliminated by adding
an additional ground and bypass capacitor in the PLL.
These are third overtone (21.6 MHz) products of the PLL IF
(7.2 MHz). This applied to all units before S/N 111xxxx.
Procedure.
- Remove the top cover (4 screws).
- Remove the rubber conductive shield.
- Remove the aluminum cover from the PLL unit
X50-1670-xx (17 screws).
- As illustrated, solder a jumper between the DBM and
VCO compartments.
- Solder a .01uF 50V disc ceramic capacitor
(CK45F1A103Z) from the DBM shield to the case of Q4
(3SK76 or 3SK92).
- Reverse steps 3-1 to reassemble.
Note: Installation time for this procedure is ½
hour or less.
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Remember it is Illegal to transmit out of band. This Modification is for
Informational purposes ONLY.
Doing such modifications on your radio may void any warranty and damage your equipment.
All mods found on this database are offered to me by other amateur radio hams or captured by Packet system.
KB2LJJ take no responsibility or liability for any damage done resulting from any modification.
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