A simple test for the PK232 =========================== Are you having trouble connecting to others with your PK-232? Are you even having trouble doing the local loopback test as per page 2-4 & 2-5 in the manual? Try both VHF and HF modes for this test. The HF test is more critical because of the narrow shift. Do the LEDs on the TUNE display light up evenly either side of centre when you do the above tests? (all LEDs illuminated except the extreme end ones.) It may be that your PK-232 tones are off frequency. The following is the simple procedure to check your tones and adjust them if necessary. Enter "VHF ON" to set the TNC into the VHF mode and select the wide shift tones. Refer to Page 6-30 in the PK-232 manual. This explains part of the procedure. When the "CAL" command is issued the screen will display the current tone frequency (and the part number of the pot to be adjusted) updated about twice per second. Pressing the space bar toggles the frequency and the other tone can be checked. After checking/adjusting the VHF tones pressing the "H" key should change to the narrow shift HF tones. Repeat as above to check these also. It pays to go back over each adjustment a couple of times. The "CAL" command is also useful for setting transmitter deviation etc., if test gear is available. "Q" quits the calibration mode and returns to the "CMD:" prompt. The table below lists the frequencies and the pots to be adjusted to set them to the correct values. Mode Freq Pot to Adj ------------------------- VHF 1200Hz R167 VHF 2200Hz R165 HF 2110Hz R168 HF 2310Hz R164 I find it puzzling that this simple procedure and information is not in the othewise mostly excellent handbook. Phil VK4APA PK232 problems ============== The following is a response to queries about PAKRATT PK-232 to A.E.A. in the U.S.A. LOSS OF TNC MEMORY whilst disconnected from computer (stand-by) & lock-up of memory: 1. It is very important to keep power above 12v.including any ripple. It may help to put a large capacitor across the supply or even to float a battery across it. 2. Locking-up when the terminal is re-started: Try the following sequence: CTRL-Q CTRL-X CTRL-Q CTRL-X. This flushes the RS-232 buffer & releases any software inhibiting flow control. Early Z-80 models had reset control circuit problems. Ensure U-16 is a 74HC14. LACK OF SENSITIVITY: 1. Change R35 (20Kohm 1/4w 5%) to 39Kohm 1/4w 5%. 2. Add a 0.047uf Mylar 10% Cap between R79 and pin 14 of U26. FREQUENCY DRIFT: This is due to an incorrect C58 (Blue 223J X7R) behind the bar-graph tuning meter. It should be a Yellow 0.022uF NPO ceramic. After replacing C58 and before reassembly power up and reset the AFSK tones: Type CAL (the freq and resistor to adjust appears). Toggle SPACE (mark & space) and H (HF & UHF tone pair) for the following European LOW tones: R164 = 1260Hz ; R165 = 2200Hz ; R167 = 1200Hz ; R168 = 1460Hz. (Thus, for example, to reset the 1260Hz frequency, variable resistor R164 would require adjustment.) VOLUME,SQUELCH & THRESHOLD ADJUSTMENTS For FM: Page REV E,F,G, (pp.2-8): Steps 1-14 are incorrect. (Note: Vol. & SQ. are radio adjustments; Thres. is a TNC adjustment) The following steps should be revised/added: 11. Radio OFF: Thres. fully clockwise, DCD now ON. 12. Turn Thres. SLOWLY until LED just goes out. 13. Radio ON & at Receive. 14. Turn Vol. & Sq. FULLY Anti-clockwise. 15. If DCD is ON, turn Thres. anti-clockwise to JUST turn it OFF. 16. Turn Vol. slowly until DCD just lights. 17. Turn SQ. slowly until DCD LED just goes OUT. Threshold setting should be between 1 & 3 o'clock. SSB operation is correct. * December 30th.Firmware * In default state, packets received BUT TOO LOW to light the LCD will NOT be displayed on screen. When doing the Loop-Back test, the AFSK level may be too low to light the LED which would indicate failure when, in fact, 232 is operating normally. It is RECOMMENDED that the AFSK level should be JUST high enough to light the DCD LED,or Loop-Back test will fail. GW6ZHQ @ GB7ABC PK232 MODS FOR OP AMPS 10-03-89 =============================== There is a lot of rubbish appearing across the pins 4 and 11 of U23, 26, 28, 30, 32 and 34, so I wired some 1uF capacitors across them. My receive noise is now much less (measured on a mark-space scope cross-display). In fact, I can now even copy some steady signals that don't even raise the S-meter needle. The capacitors used were from Radio Shack (Tandy in UK). I purchased six 1uF 35V tantalum capacitors and they were mounted on the bottom of the board with the shortest possible leads in the positions as described above. I consider the results to be outstanding. RTTY signals I could not copy before now copy perfectly, even when the scope traces are barely discernible. ARQ links which could not be made before now flow smoothly. The only thing I'm unsure about is if the mod will work without the latest version of PK232 firmware being fitted. Somehow, though, I think it will, and it's easy to try (and reverse if not liked). The most difficult part of the mod is identifying the op-amps and pinouts, but here is a hint. The pins 4 and 11 are the middlemost pins on both the top and bottom rows of the chip, so it's really hard to make a mistake. This file was downloaded from NW5K (Napoleonville, Louisiana) during an Amtor QSO on 28MHz, 2.12.89 by Ray, G3IOI @ GB7ESX PK-232 HF RFI ============= This mod. will help reduce HF RFI from the PK232. Connect 1uF tantalum capacitors between pins 4 and 11 of op-amp chips U23, 26, 28, 30, 32, 34 in order to reduce the noise on the power supply lines to these chips. 73 DJ2HZ SYSOP DL0YB PORTED AND REALIGNED FROM PC TO AMIGA FORMAT BY BOB G0LBQ - N6XDI.