With additional information added to Roy's original instructions in Italics. As always this information is provided for your information. You are responsible: 1. to verify the information in your equipment manuals, and 2. for any modifications you make to your equipment.
BE CAREFUL OF AQS PIN 13 AND ACC(1) PIN 7. They carry 13.8 volts and can damage things if accidentally shorted to other pins! I cut them off on the solder side of my cable plugs.
By the way it will be necessary to disable the beep tone that occurs when you depress a key on the IC-475. The beep tone is sent through the speaker system and will interfere with the 1200 bps data signal otherwise. The beep tone is disabled by rotating R348 (Beep Sound Level Adjustment) counter clockwise. See Section 9, p42 of the users instruction manual for a photo.
In my IC-475, I have also changed out the FL4 (Muratta CFW455-E) for a wider filter. The CFW455-E is a +/- 7.5kHz (15kHZ) filter. I first tried using a CFW455-D, a +/- 10.0kHZ (20kHz) filter with a definitely noticeable, but not terrific improvement. I then changed out this filter for a SFH455-D Gaussian shape filter designed for data reception. There seems to be a further small improvement with this filter but not such that I can place numbers on it. In addition the S-Meter must be recalibrated if you want it to read correctly with this last filter. It reads low. I think the CFW455-D is the way to go and still have the S-Meter still behave.
73, Roy -- W0SL
FUNCTION TNC RADIO PORT IC-475 AQS IC-275 AQS
TX AUDIO 1 - 2 ##
GROUND 2 9 -
2 - 1
PTT 3 - 7
RX AUDIO 4 5 # -
RF DCD 5 - -
I asked Roy for some additional direction and he sent the following information to me:
PIN 5 of the AQS PORT has a shielded cable running from it to a plug which is designated as P13. This plug is near PIN 9 of IC6 (FM Discriminator output ). By careful bending of a small plastic tab on the side of the plug, the shielded cable and its female connector sleeve can be removed from the white plastic plug housing. The female sleeve is slipped over one of the leads of a 5 to 10 mfd non-polarized capacitor. The other lead of the capacitor is soldered to a bare wire on the board which runs to PIN 9 of IC6. This is done so you do not have to solder directly to PIN 9 of IC6. The bare wire is not removed to do this. This provides a convenient access to PIN 9 of IC6 of the IC-475. The capacitor is used for DC blocking purposes. This setup / modification allows you to use PIN 5 of the AQS Socket for 9.6 Kb audio reception without having to make changes to the wiring of the AQS Socket wiring.
## Transmit audio can be input on AQS socket PIN 2 without modification. It goes to P12 on lead AQTN and drives Q33 through trim pot R152. Q33 provides plenty of gain to modulate the rig and does not seem to distort the transmit audio. You can adjust the transmit gain either in the modem or by using R152. I use R152 because I use the modem to drive both the IC275 on UO22 and the IC475 on local 9600 bps packet. That way I can independently set the transmit audio level for both rigs and switch the TNC between them.
The IC275 can be used for other modes with the TNC hooked up to the AQS port but:
when using the rig for other modes of operation. Otherwise the TNC data Carrier will also modulate the rig causing interference in the form of a hiss.
FUNCTION PSK MODEM IC475 IC275
PORT ACC(1) ACC(1)
____________________________________________________________
UP/DOWN UHF 5 1* -
GROUND UHF 1 & 2 2 -
VHF 2 - 2
PTT VHF 3 - 3
Tx AUDIO VHF 1 - 4
Rx AUDIO UHF 4 5 -
VHF 4 - 5
* A wire is added from the mic connector pin 3 to ACC1 - PIN 1 - in IC-475. The MIC connector PIN 3 is available on a small circuit board immediately behind the mic socket. The socket is wired to this board via a small ribbon cable. ACC1 - PIN 1 - is not connected to anything so the new wire must be soldered directly to PIN 1 of ACC1. Fortunately it is on the side of the socket nearest the side of the rig and is accessible with a bit of care. This wire is necessary only if you don't want to access it through the mic socket. I like all my cables on the rear of the set. Also - this wire is needed only if you are using the PSK modem UP/DOWN pulsing capability to keep you rig tuned to the downlink signals.
FROM: Roy Welch, W0SL - Minor additions and changes to text.
Note: Creative use of an in line 5 PIN DIN switch box will enable you to use the DSP2232 - or similar TNC setup - for 9k6 satellite operations OR 9k6 Terrestrial Packet operation using the IC-275 (or IC-475). In addition, I have set the switch box up in order to allow me to use Port 1 of the 2232 with the TS-690s and Port 2 for 1200 AFSK Terrestrial packet with the IC-275 as well! This permits HF, VHF, UHF or gateway operation between two of those bands when the DSP-2232 is not in use for satellite operations.
If you are interested in the details for such a setup, let me know.
TNC RADIO PORT IC275 AQS SOCKET
FUNCTION PINOUT
_________________________________________________________
TX AUDIO 2#
GROUND 1
PTT 7
Rx AUDIO 5*
Rf DCD -
This minor modification can be done in the following way:
Place the rig upside down on its top cover, with the VFO tuning knob facing you, once the bottom of the IC-275 is off. The MC3357P CHIP or FM Discriminator Chip is located on the Main Board about 4 inches from the front of the rig on a line that bisects the tuning knob of the VFO. It is labeled IC6. PLUG 13 is about one half inch to the left and slightly behind MC3357P (IC6) as you view the Main Board and IC6 from the front of the rig. The PLUG is white in colour. PLUG 13 is aligned vertically to the front of the rig and contains 9 wires. The AQAO wire in my radio is the fourth (4th) wire from the end of the PLUG which is closest to the rear of the rig. The wire is BLACK in colour in my IC- 275a and is directly connected to AQS Socket PIN 5. Note that you count from the back side of the rig along the plug to get wire 4 (black).
The plastic retaining tabs for each individual wire on PLUG 13 are located on the left side of the jack in my radio. They appear as rectangular slim pieces which are vertically aligned in relation to the Main Board. Each wire has its own retaining tab. By careful bending of the appropriate tab on the side of the plug, the shielded AQAO cable and its female connector sleeve can be removed from the white plastic plug housing. Use a very fine, non conductive probe to do this. It came out easily in my radio. You may have to move a wire harness which runs beside PLUG 13 in order to see the retaining tabs clearly. There is a female sleeve attached to the end of the AQAO wire which was removed from the PLUG. The female sleeve is slipped over one of the leads of a 5 to 10 mfd non-polarized capacitor.
The other lead of the capacitor is carefully soldered to a bare WIRE (W64) located on the Main Board which connects to PIN 9 of IC6. PIN 9 of MC3357P (IC6) is the AUDIO OUTPUT of the FM Quadrature Discriminator section of IC6. W64 is located as follows:
PIN 9 OF MC3357P (when looking at the layout of the Main Board from the front of the rig when it is on its back - VFO KNOB is at the front) is the left rear most pin on MC3357P (there are 16 pins with PIN 1 being the pin to the front right of IC6 as you look at it from the front of the rig). Now look on a vertical line to the back of the rig from PIN 9. Three to five mm (3 to 5 millimeters) from PIN 9 along this imaginary line is the start of the bare wire which is labeled W64. It travels backwards on the Main Board for about half an inch or so immediately to the left of coil L23. The wire is located between JACK 13 and L23. The wire is directly connected to Pin 9. You do not need to cut this wire. The other lead of the capacitor is soldered to this wire (W64). It is much easier to solder one lead of the capacitor to this bare wire than to the IC itself. However, care MUST be taken in soldering this connection due to the wire's proximity to other components on the board.
1) Prise off the top shield of the PLL board and pivot it on the metallic tape between it and the adjacent board shield. It is only necessary to pivot it about 90 degrees.
2) Remove the 5 PLL unit mounting screws.
3) Remove small co-ax plug (P1) from PLL board to J2 on RF YGR board.
4) One can then pivot the PLL unit in the same direction as its shield.... feeding the co-ax lead to P1 through the aperture in the chassis at the same time. There is no need to disconnect anything else.
5) The 2 unused ACC and AQS pins are now nicely assessable. Indeed pin #11 of the AQS socket has a PCB track out to a small PCB pad, so its quite easy to wire the 2 unused pins in parallel and thence to the mic socket.
6) Reassembly is the reverse of the above..ensuring that the small co-ax lead is eased through the aperture as the PLL unit is moved back into position. I hope the above notes may give others confidence in gaining access to that unused pin on the AQS socket. Ron, VK4BRG.
Last Modified 9 June 1997 by VY2DCS