|
|
|
Who's Online
There currently are 6025 guests online. |
|
Categories
|
|
Information
|
|
Featured Product
|
|
|
 |
|
|
There are currently no product reviews.
 ;
A site where discontinualed schematic diagrams and back dated information can be found on discontinued radios tv's and any electronic equipment can be found. Newer manuals either Service and operating manuals. Radio amateurs should find this site a great source for ham radio equipment manuals. I will return to this site should I need information on any electrical equipment. priced easy to download in a PDF format and print pages need to undertake the repair.
;
Quality scan of the original. All the detail necessary to troubleshoot, repair and adjust the unit. I'm sure I will be downloading more manuals in the future as the need arises.
;
Exactly as described, a Service Manual complete with the schematics and PCB layout delivered in a timely manner. Many thanks for the great service.
 ;
some of the writing is a bit blur but the part in the schmatic was great and i have fixed the machine thanks
;
Well.. I'd searched for this manual and although I found many copies online I was pleased to find your website with a well balanced pricing system and easy to search and follow links. That together with the very quick response time was just what I was looking for.. being a very impatient tech.. ;-) I had the service manual in front of me within a short time.
Bookmarked.. and you can bet I will always come here first for my service & user manuals..
best regards
Ed(Tony) Foley
G7WHK
TK-390
CIRCUIT DESCRIPTION
4. Transmitter System
4-1. Microphone amplifier
The signal from IC3 (control unit) goes through the mute switch (Q403). When the SP-MIC is not attached, the microphone switching terminal (MSW) on the universal connector becomes High, and mute switch (Q403) is turned on. When the SP-MIC is attached, MSW is connected to GND at inside of SP-MIC. For this reason, Q403 is turned off, the internal microphone is muted, and only the input of the external microphone is supplied to the microphone amplifier of the TXRX unit. The signal from microphone passes through the limiter circuit in D601, and through the high-pass filter, the ALC circuit, the low-pass filter, the high-pass filter, and pre-emphasis/IDC circuit in IC607. When encoding DTMF, mute switch (Q601) is turned off for muting the microphone input signal. The signal passes through the D/A converter (IC603) for the maximum deviation adjustment, and enters the summing amplifier consisting of IC605 (1/2), and is mixed with the low speed data from the CPU (IC406). The output signal from the summing amplifier goes to the VCO modulation input. The other output signal from the summing amplifier passes through the D/A converter (IC603) again for the BAL adjustment, and the buffer amplifier (IC604 1/2), and goes to the VCXO modulation input.
4-3. Drive and Final amplifier
The signal from the T/R switch (D7 is on) is amplified by the pre-drive (Q6) and drive amplifier (Q8) to 20mW. The output of the drive amplifier is amplified by the RF power amplifier (IC501 or IC801) to 4W (1W when the power is low). The RF power amplifier consists of two stages MOS FET transistor. The output of the RF power amplifier is then passed through the Transmit-Receive (TX-RX) antenna switching (D10 is on) and the harmonic filter (LPF) and the Internal-External (INT-EXT) antennal switching (in the universal connector) and applied to the antenna terminal.
In the ANT universal connector EXT-INT ANT SW ON�EXT
From T/R SW (D7) +B
Q6 PreDRIVE AMP R35 R37 R39
IC501 or IC801 D10 RF TX-RX DRIVE POWER ANT AMP AMP SW Q9 VDD VGG SW
Q8
LPF
Q7 SW IC7 (1/2) IC7 (2/2)
Q13 REF VOL (IC3) SW
Fig. 7 Drive and final amplifier and APC circuits
4-4. Internal-External (INT-EXT) antenna switching 4-2. Noise cancelling microphone circuit
The two signals from INT MIC (Main & Sub) are input to the positive (+) input (Sub) and to the negative (�) input (Main) of the IC3. If the same signal is input to both Main and Sub, the Main signal is canceled at the output of IC3 (pin 7). In other words, noise from nearby sources not directly connected to the transceiver enters the Main and Sub inputs at the same signal and is therefore canceled out. When a signal is only input to Main and there is no signal at Sub, the Main signal is output as is, from IC3 (pin 7). In other words, only the voice audio of the operator in extremely close proximity to the Main MIC is input to Main so that the signal is output as is from IC3 (pin 7). Also, when the �N/C� switch is set to �L�, transistor Q14 turns off so Sub microphone turns off and operation is the same as above.
MM Q601 SW IC3 IC607 MAIN MIC SUB (CONT) Q404 IC603 D/A I4 O4 IC605 (1/2) SUM AMP LSD IC603 D/A I3 O3 IC10 IC604 (1/2) BUFF AMP VCO X1 VCXO N/C AMP MIC Q403 SW D601 LIMIT 12 HPF ALC COMP LPF HPF PRE EMP IDC 6 15 16 18 19 9 8
The INT-EXT antenna switch housed inside the universal connector only switches to the EXT ANT side when an antenna speaker-microphone has been installed. This INT-EXT antenna switch works mechanically and switches based on the operation shown in Figure 8.
EXT ANT
From LPF RF
OFF
Switch OFF � INT Internal ANT antenna
EXT ANT Switch ON � INT External ANT antenna
From LPF RF
ON
TONE
EXT. MIC
Fig. 8 Internal-External antenna switching
MSW
Fig. 6 Microphoen circuit 19
|
|
|
> |
|
