From - Mon Feb 02 01:45:47 1998 Werner: I have gathered some info for your R-71A FAQ page. I hope this adds to your own. The text is a bit long, but may be worth it ! Happiest of Holidays to you and yours. Mike Lafferty West Seneca, NY ------------------------------------------------------------------------------------------ Capacitors, etc. I have had the same trouble with the caps in the display unit. Replaced with tantalum. If your display seems to show wrong characters you should check capacitors C14, C21 and C20 on the display card. Another problem I had was a capacitor at the antenna jack. Also the power supply may cause oscillations. The voltage adjustment potentiometer when adjusted for more than 14 volts can cause the supply to oscillate! If your R71 is dead on some bands but not on others, a trimming capacitor in the PLL is making bad contact. There are 4 oscillators for 0,1-8 MHz, 8-15, 15-22 and 22-30. The capacitors are C78, C88,C97 and C107. Just tap the oscillator trimmers. If the receiver comes to live again, carefully register the position of the trimmer and turn it several turns in order to make better contact. The same kind of trimmer is in the USB BFO circuit and if the receiver drifts in USB, change this capacitor. Hard to adjust to get the frequency within the +- 10 Hz possible. My R71 performs very well, I have compared it to R70, R390A, NRD525, NRD515. It is modified with a Willco board, a 3 kHz 455 kHz filter for phase-locked AM with a ESKA PLAM card. ------------------------------------------------------------------------------------------ ? Anyone have any info on mods for this fairly excellent receiver? Don Moman of Shortwave Horizons in Canada has authored a booklet with a bunch of R71 mods. You can probably contact him through CIDX; I don’t have the address for Shortwave Horizons handy. The best mod for the R71 is the Eskab and Edvis PLAM board and their 4 kHz crystal filter. I don’t know if it is still available; they used to advertise in WRTH. This board adds synchronous selectable-sideband detection to the R71. The sync detector is excellent - it will lock on down into the noise and noticeably increases the signal-to-noise ratio on weak DX signals. The 4 kHz filter is great for program listening in the tropical bands. The stock 6 kHz position on the ICOM sucks, since it doesn’t have any filtering in the 2nd IF, and only a lousy 6 kHz cermic filter in the 3rd IF. There’s a mod that adds the 6 kHz crystal filter for the R70 to the R71’s 2nd IF; it should be almost as good as the Eskab and Edvis filter. I think the mod is described in Moman’s book. Regards, -Steve ------------------------------------------------------------------------------------------ I found a way to receive signals below 100 kHz using an IC-R71A and published this trick back in April 1985 Monitoring Times: Tricking the ICOM R71A to Tune Below 100 KHZ Copyright 1985, Bob Parnass, AJ9S The ICOM R71A general coverage receiver is designed for VLF reception down to about 97 kHz. The following steps will confuse the microprocessor-based controller sufficiently to permit reception down to 0.0 kHz: 1. If all 32 memory channels contain frequencies, use the FUNC and CLEAR buttons to clear a memory channel. 2. Place VFO/M switch into the M (Memory) position. 3. Using all the manual dexterity you can muster, rock the MAIN TUNING knob back and forth, while simultaneously rocking the MEMORY-CH rotary control to switch back and forth between a memory channel with a frequency in it and a clear memory channel. Continue rocking both the controls until a frequency of 0.000.0 appears on the digital display. 4. Depress the WRITE button. This stores the 0.000 MHz frequency in a memory channel. You can now rotate the MAIN TUNING knob clockwise to tune up from 0.000 MHz to the frequency you want. Be careful: if you rotate the MAIN TUNING knob counterclockwise, the radio will immediately revert to 29.999 MHz. To tune below 100 kHz in the future, just recall the 0.000 MHz frequency from the memory channel and use the tuning knob to tune upward. That way, you don’t have to use two hands every time you tune to a VLF frequency. I used a Wavetek 180 sweep/function generator to verify that the R71A is indeed receptive to signals below 100 kHz. -- ------------------------------------------------------------------------------------------ Capacitors, Part II I have had the same trouble with the caps in the display unit. Replaced with tantalum. If your display seems to show wrong characters you should check capacitors C14, C21 and C20 on the display card. Another problem I had was a capacitor at the antenna jack. Also the power supply may cause oscillations. The voltage adjustment potentiometer when adjusted for more than 14 volts can cause the supply to oscillate! If your R71 is dead on some bands but not on others, a trimming capacitor in the PLL is making bad contact. There are 4 oscillators for 0,1-8 MHz, 8-15, 15-22 and 22-30. The capacitors are C78, C88, C97 and C107. Just tap the oscillator trimmers. If the receiver comes to life again, carefully register the position of the trimmer and turn it several turns in order to make better contact. The same kind of trimmer is in the USB BFO circuit and if the receiver drifts in USB, change this capacitor. Hard to adjust to get the frequency within the +- 10 Hz possible. My R71 performs very well, I have compared it to R70, R390A, NRD525, NRD515. It is modified with a Willco board, a 3 kHz 455 kHz filter for phase-locked AM with an ESKA PLAM card. ------------------------------------------------------------------------------------------ Voltage Reg., Caps., etc. I have owned an R71A for almost 12 years. There are a couple of things one should be aware of when buying a used one. The electrolytic capacitors on the display board tend to need frequent replacement. When the caps go bad, the display makes lots of noise in the AM broadcast band and below. There is a circuit board just inside the case on the left-hand side, which contains another source of grief for R71A owners. One of the components on that board is a 7805 voltage regulator which runs as hot as a firecracker until it finally burns out after about 5 years of abuse. It first begins to oscillate at radio frequencies, producing strong drifty carriers that swish through the tuning ranges even when the antenna is not connected. When the regulator is near death, it sort of works when hot, but shuts down when cold. It pretty well kills the R71A until it is replaced. I finally got tired of replacing them and instead took an LM309K, which is a TO3 version of the 7805 and mounted it on the rear case. It gets about as warm as a human hand and I haven’t had a bit of trouble in several years. I think $400.00 is a reasonable price for a very fine receiver like this one, but the display and power supply problems do give one pause if one doesn’t want to have to get out the soldering iron from time to time. I have joked that Icom needs to go to power supply and display school since the R71 and R7000 receivers both seem to have lots of trouble in these areas. Otherwise, they are excellent. Martin McCormick ------------------------------------------------------------------------------------------ ICOM R71A Battery Hi, I have an R71E purchased about 10 years back and was expecting the same problem anytime. However, I have gone for the expensive option as I wanted the extra memories and VLF capability. I can’t help you with a battery type and supplier but the way to change the battery is to carefully solder a small silicon diode to the positive rail of the backup battery (cathode to the rail). Then connect a similar voltage supply or battery (maybe a tad higher to take up the 0.7V drop in the diode) between the anode end and ground. This keeps the supply alive during the change and prevents the present battery from discharging through the backup supply. Making sure the supply is complete, desolder the existing battery with an iron that is not grounded, fit the new one, disconnect the diode and Bob’s yer uncle. Actually, I think that you could get away with just removing the battery and quickly fitting another, as the rail capacitance is probably good for a few microamps while you are beavering away. 73 de G3LLV, Joe ------------------------------------------------------------------------------------------ |Icom’s R71A and R7000 both have problems with electrolytics on the |display board. There are files around [look for ICr71, R71a with that |old standby archie] that tell how to fix and with what. Worst case the |display stops working; noise is more of a black art, at least in the |R71A. |Watch out for size differences in the electrolytics - the spaces are |small, and you can contribute to the noise problem..... [The following is for the Icom R-70; I am not sure what is applicable to the R-71 because I don’t have the schematic.] Well, Sunday I replaced the AC PS bridge rectifier with the Rat Shack (Tandy) 4 Amp @ 100 PIV one. This is a real pain-in-the-ass because the PC boards holes are too small for the leads on the RS BR, so I used a knife and a file to laboriously shrink the diameter of the leads. I adjusted the voltage to 13.8V DC output as per the service manual. [I have a Rat Shack MOV surge suppressor placed across the input AC connector which I put in years ago. However, I understand these slowly degrade with time as well as being rather slow in responding the transients (You need something like a Transorb to catch the fast stuff), so perhaps I should also replace that unit as well eventually.] I obtained two 100mfd/35WVDC radial lead electrolytic caps at Rat Shack as well, to replace the 100mfd C4 & C7 electrolytic caps on the pi-network filter of the -10V output of the DC-DC converter on the fluorescent display board; however, after getting the free Rat Shack catalog, I noticed that RS now offers a 100mfd/16WVDC cap (also a 100mfd/10WVDC), but I didn’t see that one at the store. I removed the screws on the main board on top of the receiver and moved it out of the way so as to gain access to the display board. I disconnected the connector on top of the display board, and the wiring harness connector that goes to the PLL board underneath the receiver. I then removed the display board after unscrewing the two screws holding it to the top frame of the receiver. Capacitors C4 and C7 are immediately adjacent to the DC-DC converter which is the small shielded metal box on the left side of the Display board. I yanked both of these capacitors (yes, it IS a tight fit); they were both rated at 100mfd, 10WVDC, just like the service manual said. The C7 space accommodated the RS 100mfd/35WVDC cap as I was able to mount the unit flush against the PC. board. However, the C4 space didn’t have quite the space to allow flush mounting of the new capacitor; even though I tried to get a little extra space by unsoldering one of the leads on the green ceramic disk capacitor and moving it slightly. The replacement 100mfd/35WVDC cap sits slightly higher on it’s leads than the original cap now. I doubt if it makes much difference though in the suppression of EMI from the DC-DC converter (You could always use the presumably physically smaller 100mfd/16WVDC RS unit for C4, but it is a bit more expensive than the 35WVDC unit.). Results: With the display dimmer button set to normal brightness, there is a whole world of difference in the background hash. However, with the dimmer switch set to “Dim” significant “hash” is still present on some frequencies. Any ideas on suppressing the RF hash with the Dimmer set? ------------------------------------------------------------------------------------------ In article <6481pt$ano$1@news1.teleport.com>, prografx@teleport.com (Steve Kennedy) wrote: >"N4WFK" wrote: > >>Anyone heard of a mod to restore the passband tuning on the Icom 765? I >>had it with my 761 and of course the 765 lost it to I/F shift due to some >>patent problem? > >>Thanks in advance. > >>John, N4WFK > > >I can't speak about these models, but I have restored R71A receiver's >that lost their PBT controls. Your mod may or may not be similar in >nature: > > >1. In the IC-R71A, the dual PBT/Notch control is replaced with a >single (for Notch only). The PC board is the same inside, so you have >to replace the control (potentiomenter) ($15) and both external knobs >($4) to restore this part. The second (rear PBT) element is jumpered >to bypass these connections. > >2. If you want the front panel nomenclature to show PBT for this new >control, you will have to order the appropriate front panel casting >(about $45). > >3. You need to put the PBT IF filter back in. The factory stock >unit is about $55, the better FL-44A is over $200 new now (whew). >There is a spot on the PC board for it... it simply was replaced with >a coupling resistor to bypass this part of the layout. > >So, simply removing this resistor, adding the filter back in and >restoring the control is all that is electrically required. The front >panel is optional. If you do the front panel, make sure you get the >logo plate and new window to go with it. > >GET THE SERVICE MANUALS! > >I found all all I needed to know about these changes from the Icom >factory Service Manuals, including part numbers. It also helped me to >compare the schematics for both old and new R71A to the even older R70 >(which is almost identical RF-wise). > >I hope this might help you in your investigation for the 761/765! > >Steve >WB7PSD > Actually it is much simpler than this for the 765. E-mail me if you still need it. Dave David Wells KD6TO (KD6 Teletype Operator) FCC GROL with Radar and GMDSS Maintainers License NMEA Certified INTERNET: davew@cruzio.com (remove the xyz) OPINIONS EXPRESSED ARE MY PERSONAL ONES AND DO NOT REPRESENT THOSE OF MY EMPLOYER ------------------------------------------------------------------------------------------ MODIFICATIONS TO THE ICOM R71A IF FILTER SELECTION CIRCUIT by Greg Doerschler (gkd@wpi.edu) This article may be distributed or reposted freely provided that it remains completely intact. INTRODUCTION: Simple modification to the IF filter selection circuit of the ICOM R71A general coverage receiver can provide additional bandwidth selection options in receivers which have been equipped with the optional FL-44A high grade 2.4 KHz crystal filter (or equivalent). In the AM mode, the modification enables a 2.8 KHz bandwidth to be selected in addition to the 6 KHz and 2.4 KHz bandwidth settings which the “FL-44A”-equipped R71A already offers. In the SSB, CW and RTTY modes, the modification can be used to enable the PBT knob to function as either a passband tuning control or an IF-shift control. The potential benefit of this modification depends to a large extent on how the receiver is used. R71A owners considering the modification should take some time to decide whether it is worth the effort before proceeding. Much of this article discusses the rationale behind the modification and explains its actual effect. The procedure itself - described at the end of the article - is not very complex, but it does involve some delicate soldering and the ability to read schematic diagrams and identify components on the PC boards. I can attest that my modified R71A performs as indicated, but I assume no responsibility for the outcome of anyone’s modification efforts. Make sure you understand and are comfortable with what you are doing, and proceed at your own risk. While not absolutely critical in this case, it is generally smart to have a service manual handy when modifying equipment. BACKGROUND: Intermediate Frequency (IF) bandwidth filtering in the R71A is accomplished by filters in the 9 MHz 2nd IF stage and in the 455 KHz 3rd IF stage. The stock R71A comes with the following standard filters: 2nd IF: FL-70 (2.8 KHz) 3rd IF: CFW455IT (6 KHz) FL-30 (2.3 KHz) CFJ455K5 (2.8 KHz) While the 2nd IF filters are of reasonable quality, the 3rd IF filters are inexpensive ceramic filters. ICOM offers the FL-44A 2.4 KHz high grade crystal filter as an optional replacement for the 2.8 KHz CFJ455K5. Other filter manufacturers have comparable replacements available too. One of two optional (additional) CW filters may also be installed in the 2nd IF; the FL-32 (500 Hz) or the FL-63 (250 Hz). With only its stock filters, the R71A utilizes the following filter combination in its various modes: 2nd IF 3rd IF AM wide...............(none)................ 6 KHz (CFW455IT) AM normal............ 2.8 KHz (FL-70)....... 2.8 KHz (CFJ455K5) SSB/CW/RTTY wide..... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT) SSB/CW/RTTY normal... 2.3 KHz (FL-30)....... 2.8 KHz (CFJ455K5) At first glance, one might think that it would have been more logical to use both 2.8 KHz filters in the SSB “wide” position (similar to the AM “normal” position), rather than a 2.8 KHz filter followed by a 6 KHz filter. (Since the narrower of the filters in the IF chain really determines the overall bandwidth, the 6 KHz filter is actually doing nothing.) However, if things had been set up this way, replacement of the 2.8 KHz 3rd IF filter with the optional FL-44A 2.4 KHz high grade crystal filter would have restricted the SSB “wide” bandwidth to 2.4 KHz. The SSB “wide” and “normal” bandwidths would then have been virtually identical. Observe that the installation of the FL-44A does in fact reduce the AM “normal” bandwidth from 2.8 KHz to 2.4 KHz. Here’s how the filter chart would look for an R71A with both the optional FL-44A and the optional FL-32 CW narrow filter installed: 2nd IF 3rd IF AM wide.................. (none)................ 6 KHz (CFW455IT) AM normal................ 2.8 KHz (FL-70)....... 2.4 KHz (FL-44A) SSB/CW/RTTY wide......... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT) SSB/CW/RTTY normal....... 2.3 KHz (FL-30)....... 2.4 KHz (FL-44A) Narrow-all modes......... 500 Hz (FL-32)....... 2.4 KHz (FL-44A) Having the razor sharp 2.4 KHz bandwidth of the FL-44A accessible in the AM mode can sometimes be great for critical DXing, but AM audio at that bandwidth does lack sufficient fidelity for comfortable listening. With some minor rewiring of the filter selection hardware, the 2.8 KHz AM bandwidth can be restored in “FL-44A”-equipped R71A receivers. This is done by making the AM “normal” setting select the same 2.8 KHz (FL-70) / 6 KHz (CFW455IT) filter pair which is used in the SSB “wide” setting. For experimental purposes, I had temporarily configured my R71 to select this filter pair in the AM “wide” setting in order to make direct receive fidelity and skirt selectivity comparisons against the 2.4 KHz AM “normal” setting. My findings revealed that with the receiver tuned directly to a broadcast station, both bandwidths produced very similar sounding audio without much fidelity. But by tuning the R71A’s main tuning dial 1.5 KHz away from the AM carrier frequency, the 2.8 KHz filter passed the carrier and enough of one of its sidebands to provide halfway decent fidelity. (It was noticeably less than the 6 KHz bandwidth, but still quite usable.) The same trick was also tried with the narrower, 2.4 KHz passband by tuning the main dial 1 KHz off frequency; but even then the fidelity was still too restricted for comfortable listening. Since the 2.8 KHz bandwidth seemed to isolate noisy AM signals just as well as the 2.4 KHz setting in most of my tests, I had initially considered replacing the 2.4 KHz setting with 2.8 KHz in order to take advantage of the additional fidelity. However, I did encounter some relatively rare instances when trying to tune in a weak AM station adjacent to a strong local broadcaster where the 2.8 KHz/6 KHz filter pair allowed some odd residual noise from the strong adjacent signal to become embedded in the desired signal. The noise was not there when using the 2.8 KHz/2.4 KHz filter pair. This revelation led me instead to devise a way of making both bandwidths available in the AM mode (in addition to the 6 KHz bandwidth). TECHNICAL DISCUSSION: For the following technical discussion of the IF filter selection circuit of the R71, you may wish to refer to your schematic diagram or service manual. The filter select IC is IC3 on the main PC board. It has three input pins (pins 9, 10, and 11); the logic state of which are determined by the operating mode (AM, FM, SSB/CW/RTTY) and by the position of the “wide” and “narrow” filter switches on the front panel. The configuration of these settings determines which IC output pin goes high. (Output pins are pins 1, 2, 4, 5, 12, 14 and 15.) Diodes connected from the output pins to the various filters determine which filters are activated by each specific mode-bandwidth combination. There are two output pins (pins 1 and 4) which are only activated in the FM mode. These outputs are unused (not connected to anything) since the optional FM board has its own IF filter which is automatically selected in the FM mode. The following table from the service manual shows the input-output relationship of IC-3: INPUT PIN MODE 9 10 11 OUTPUT PIN SSB/CW/RTTY normal L L H 14 SSB/CW/RTTY wide H L H 5** SSB/CW/RTTY narrow* L H H 12 AM normal L H L 15 AM wide H H L 2 AM narrow* L H H 12 FM normal H L L 1 FM wide H L L 1 FM narrow* H H H 4 ? assuming optional filter switch (S1 on main PC board) is ON. ** this output was incorrectly listed as pin 3 in the service manual. There are two wires which send logic data from the filter switches on the front panel to the IC input pins. One goes high when the “wide” button is depressed and the other goes high when the “narrow” button is depressed. The switches are deliberately interconnected in such a way that both wires are low when the switches are simultaneously depressed (just like if neither switch were depressed). By installing two solder bridges on the PC board where the switches are mounted, this interconnection can be defeated so that both wires will go high when the switches are simultaneously depressed. Doing this causes one of the unused “FM” output pins on the filter select IC (pin 4) to be activated in any mode. Installing diodes from this pin to the IF filters essentially provides an additional filter selection option. I decided that my AM normal “both switches out” configuration would be the 2.8 KHz setting (2.8 KHz FL-70 and 6 KHz CFW455IT), and that the “both switches in” configuration would be the narrower setting employing the 2.4 KHz FL-44A in the 3rd IF. But rather than use the 2.8 KHz (FL-70) filter in the 2nd IF for this narrower setting, it made more sense to use the 2.3 KHz (FL-30) instead since the FL-30’s bandwidth more closely matched that of the FL-44A. There was another advantage to setting the options up this way. The “both switches in” bandwidth selection is the same in all reception modes. Since the FL-30/FL-44A combination was already the “normal” (both switches out) SSB/CW/RTTY selection, I had the opportunity to change that selection without losing access to the FL-30/FL-44A filter combination in the SSB/CW/RTTY modes. By making the SSB/CW/RTTY “both switches out” setting use only the FL-44A in the 3rd IF (bypassing the 2nd IF filters altogether), the passband tuning control would act like an IF-shift control when this setting was selected. I found this option to be useful when tuning in AM broadcast stations in the SSB mode using ECSS reception. By adjusting the IF shift function so that the passband was centered directly over the AM carrier, the upper and lower sideband components could be heard beating against each other. The main tuning dial could then be adjusted until a “zero beat” was heard; indicating that the signal was properly tuned. Note that since bypassing the 2nd IF filters does reduce the dynamic range of the receiver, use of the IF-shift function in the presence of very strong signals on nearby frequencies may impair reception (similar to what happens in the AM wide position). With the above changes done, here’s what my filter selection configuration would look like: 2nd IF 3rd IF AM, wide button in............. (none)................ 6 KHz (CFW455IT) AM, both buttons out........... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT) SSB/CW/RTTY, wide button in.... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT) SSB/CW/RTTY, both buttons out.. (none)................ 2.4 KHz (FL-44A) ALL MODES, both buttons in..... 2.3 KHz (FL-30)....... 2.4 KHz (FL-44A) ALL MODES, narrow button in.... 500 Hz (FL-32)....... 2.4 KHz (FL-44A)** ** This bandwidth is of no use in the AM mode, but there is no way to change it without affecting the other modes as well. The only negative consequence of these changes is that operation of the filter select switches is a bit more complex, but I found it became second nature very quickly. PROCEDURE: There are many possible ways that the filter selection circuit could potentially be modified. I will detail three options: (1) Implement the modification exactly as I have described above. (2) Implement the modification exactly as I have described above, except use the “narrow” filter switch rather than the “both switches in” configuration to access the extra bandwidth setting. This may only be done if no optional CW narrow filter has been installed. (3) Replace the 2.4 KHz AM “normal” bandwidth with 2.8 KHz. Make no other changes to the filter select circuit. These three options are listed in decreasing order of complexity. Options 1 and 2 produce identical results, except that different filter switch positions are utilized. Options 2 and 3 only require the top cover of the R71A to be removed. Option 1 requires that both the top and bottom covers be removed so that the front chassis can be partially removed to access the filter switch PC board. For option 1, you will need two small general purpose switching diodes. No additional components are required for options 2 and 3. A short length of thin flexible insulated wire will be needed to make a few small jumper connections. PREPARATION: Read the procedures and make sure you have all the necessary part and tools on hand. I suggest taking all appropriate anti-static precautions whenever working on radio gear. Be sure power is disconnected from the receiver. Use only a low wattage, fine point soldering iron. It is important to use as little heat as necessary for all solder connections on the top side of the main PC board to avoid melting the solder on the underside. [Remember, these modifications will only be of potential benefit if the optional FL-44A crystal filter (or equivalent) has been installed. Some dealers also offer 4 KHz filters as replacements for the 6 KHz CFW455IT ceramic filter in the 3rd IF. Installation of these replacement filters should not have any effect on the results of the modifications.] OPTION 1 - CHANGES ARE IMPLEMENTED EXACTLY AS DISCUSSED IN THE PRECEDING TEXT: A. Remove the top and bottom covers. Place the receiver (top side facing up) on a stack of magazines or large books at least 2” thick. Only the metal chassis should rest on the stack, not the front panel. B. You will see two flathead screws on either side of the receiver which hold the front chassis assembly to the main chassis. Remove only the top screw on each side and loosen the lower ones slightly. Using the lower two screws as a hinge, carefully fold the front assembly down so that the face of the radio rests on the desk. (A soft cloth may be used to prevent scratches.) C. Right beneath the back of the S-meter, you will see a PC board to which the wide and narrow filter switches connect. Locate the 12 solder points in a straight row associated with the two switches. There is a slight gap between the switches which contains two additional solder points just above and below those in the line. (The board layout diagram supplied with the service manual is quite helpful in locating the appropriate solder points.) You need to create solder bridges across the outermost set of normally open/normally closed switch contacts for each of the two switches. The appropriate pins are shown below: wide switch narrow switch bottom of radio ^ . | XX=solder . .XX. . . . . . . .XX. . | bridge . D. Inspect your work. Carefully return the front assembly to its proper position and secure the four flathead mounting screws. Re-install the bottom cover. E. Turn ON the filter switch (S1) on the main PC board. This switch will already be on if an optional CW narrow filter has been installed. S1 is a small slide switch not far from the center of the board. F. You may wish to verify that everything is working OK so far. If so, be sure that all tools, etc. are out of harm’s way and reconnect power, antenna and an external speaker to the receiver. The bandwidth switches should work the same as before, except that (1) there will be no receive with both switches pushed in and (2) there will be no receive with the “narrow” switch pushed in unless an optional CW filter is installed. Disconnect power again once the tests are complete. G. Locate D37 on the main PC board right next to IC3 near the center of the board. Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D37 to the cathode (top) lead of D39 (located on the opposite side of IC3). H. PERFORM THIS STEP ONLY IF YOU WISH TO MAKE THE “IF-SHIFT” MODIFICATION FOR THE SSB/CW/RTTY “BOTH SWITCHES OUT” POSITION, AS DISCUSSED IN THE PREVIOUS TEXT. IF YOU ONLY WANT THE EXTRA AM BANDWIDTH, SKIP TO STEP “I.” Cut the top (cathode) lead of D44, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up and solder a jumper wire from it to the top (cathode) lead of D42 (located near filter switch S1). I. A switching diode must be connected from pin 4 of IC3 to the top (cathode) lead of D36 (located right next to D37). A second diode must be connected from pin 4 of IC3 to the lead sticking out of the PC board which was clipped from D44. If D44 was not clipped in step H, the diode just connects to top (cathode) lead of D44. To make the IC3 connection, tin both pin 4 and the lead which will connect to it; then place the two in contact with each other and heat up the connection. I performed this step by first soldering the anode of one of the switching diodes to the anode of the second; right where the lead enters its base. I then cut the anode lead of the first diode to a fairly short length and soldered it to pin 4 so that the two diodes were held in a vertical position just a tad above the IC. I then clipped the two cathode leads very short and ran insulated jumper wires from one cathode to D36 and from the other cathode to the D44 clipped lead coming out of the PC board. However you decide to do it, make sure the IC3 connection does not short out any other pins and make sure the switching diode leads cannot come in contact with any other components. J. Inspect your work and verify all steps were done properly. Make sure all tools are out of harm’s way and test the modification. If everything works OK, reassemble the receiver. Note that with this modification, the narrow button must be in the “out” position for the FM unit (if installed) to function properly. OPTION 2 - CHANGES ARE IMPLEMENTED EXACTLY AS DISCUSSED IN THE PRECEDING TEXT EXCEPT THE “NARROW” FILTER SWITCH IS USED INSTEAD OF THE “BOTH SWITCHES IN” CONFIGURATION TO ACCESS THE ADDITIONAL BANDWIDTH. THIS OPTION MAY ONLY BE USED IF NO CW NARROW FILTER HAS BEEN INSTALLED IN THE RECEIVER. A. Remove the top cover of the receiver. B. Turn ON the filter switch (S1) on the main PC board. S1 is a small slide switch not far from the center of the board. C. Locate D37 on the main PC board right next to IC3 near the center of the board. Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D37 to the cathode (top) lead of D39 (located on the opposite side of IC3). D. PERFORM THIS STEP ONLY IF YOU WISH TO MAKE THE “IF-SHIFT” MODIFICATION FOR THE SSB/CW/RTTY “BOTH SWITCHES OUT” POSITION, AS DISCUSSED IN THE PREVIOUS TEXT. IF YOU ONLY WANT THE EXTRA AM BANDWIDTH, SKIP TO STEP “E.” Cut the top (cathode) lead of D44, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up and solder a jumper wire from it to the top (cathode) lead of D42 (located near filter switch S1). E. Cut the top (cathode) lead of D46 (located a little toward the front of the main PC board). Make sure the two clipped leads are not touching. F. Locate D45 on the main PC board (near IC3). Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D45 to the lead sticking out of the PC board which was clipped from D44. If step D was not performed, then solder the jumper to the cathode (top) lead of D44. G. Inspect your work and verify all steps were done properly. Make sure all tools are out of harm’s way. Reconnect power, antenna and an external speaker, and test the modification. You should now have the following bandwidth settings: AM wide................ 6 KHz (CFW455IT) [no change] AM normal.............. 2.8 KHz (FL-70/CFW455IT) SSB/CW/RTTY wide....... 2.8 KHz (FL-70/CFW455IT) [no change] SSB/CW/RTTY normal..... 2.4 KHz (FL-44A) [IF-shift, if step D was or performed] SSB/CW/RTTY normal..... 2.3 KHz (FL-30/FL-44A) [no change, if step D was not performed] Narrow, all modes...... 2.3 KHz (FL-30/FL-44A) If everything works OK. reassemble the receiver. OPTION 3 - REPLACE THE 2.4 KHz AM “NORMAL” BANDWIDTH WITH 2.8 KHz. MAKE NO OTHER CHANGES TO THE FILTER SELECT CIRCUIT. A. Remove the top cover of the receiver. B. Locate D37 on the main PC board right next to IC3 near the center of the board. Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D37 to the cathode (top) lead of D39 (located on the opposite side of IC3). G. Inspect your work and verify it was done properly. Make sure all tools are out of harm’s way. Reconnect power, antenna and an external speaker and test the modification. Your AM “normal” bandwidth will now be 2.8 KHz (FL-70/CFW455IT) instead of 2.4 KHz (FL-70/FL-44A) If everything works OK, reassemble the receiver. ------------------------------------------------------------------------------------------ This article appeared in the Ontario DX Assoc Newsletter. Hope it helps. Tom Modification of the R-71A to 37 Mhz TF Marcotte, N5OFF n5off@w5ddl.aara.org This article will cover the use of the Willco Electronics Company¹s ICM-1024 No-Fail memory board for Icom products as a means of achieving a 37 Mhz upper frequency limit for the Icom R-71A receiver. This modification is done without tampering with the RF circuits of the radio. Caveat: Don¹t attempt this modification if you are uncomfortable with soldering small electronic devices. With that said, lets continue. Some Icom products, the R-71A and the IC-751 to name two, have a volatile random access memory (RAM) board which stores the radio¹s operating parameters (i.e. band limits) as well as 32 user programmed memories. The RAM is kept alive by a small lithium battery. In most cases, the battery should last a long time, ten years or more. Battery health may be assessed at any time by comparing its present voltage to an approximate 2.7 volt warning level. If by some chance this battery should fail before you¹ve had the opportunity to solder in a new one, then the board (not the whole radio) must must be returned to Icom for replacement of the battery, and for reprogramming of the RAM chip. Willco Electronics markets a product called the ICM-1024 No-Fail memory board. This product has two key features: 1). The board offers the user 32 x 32, or 1024 memories. 2). The board has the radio¹s operating parameters stored on a read-only memory (ROM) chip. In other words, there is no danger of the radio becoming inoperative due to battery failure. The Willco board does in fact have a RAM chip and battery like the Icom, but this chip holds only the memories, not the operating parameters. If the Willco battery fails, then one would only lose the memories (albeit 1024 of them!). It should be stressed that careful replacement of the battery on either of the boards when the voltage drops to 2.7 volts will prevent a memory loss of any kind. Installation of the Willco board is relatively straightforward, and well documented in the instructions. Mechanically, the board (not a kit) presses right down into the original Icom connectors. To enable the 1024 memory capability, one must make one logic unit connection and eight connections to two chips in the radio¹s matrix unit. The instructions don¹t mention that you can get the no-fail capability and 32 memory function by not wiring the board in at all, just press it down to the original board¹s connectors. This may be a good alternative to solder-shy users. Being that the Willco board holds the operating parameters, the company took the opportunity to extend the primary default upper band limit to 31.0 Mhz (the lower limit is moved as well, from 100 KHz to 10 Khz). The default limit was not programmed higher than this because the Icom R-71A (and the IC-751 as well) shut down at that frequency. That is, the Icom control chip that tells the radio to turn on the proper VCO (one of four) and bandpass filter (one of five) for the top band doesn¹t address frequencies higher than 31.0 Mhz with its factory wiring. When the frequency exceeds 31.0 Mhz, all VCO's and bandpass filters are switched off. The Willco boards of post December 1993 manufacture have an alternate upper frequency limit of 55 Mhz programmed into a separate R-71A program location. This location can be accessed by jumpers. The jumper configurations for the various radios that the Willco board supports are: JP01 JP02 JP04 JP08 Icom Radio Note 0 0 0 0 R-71A 31 Mhz upper limit 1 0 0 1 R-71A 55 Mhz upper limit 1 0 0 0 IC-745A 0 1 0 0 IC-751A 1 1 0 0 IC-271A 0 0 1 0 IC-471A 1 0 1 0 IC-251A 1 1 1 0 M700 Marine Radio With the jumpers installed properly, the radio will now program up to 55 Mhz, but will only operate up to 31 Mhz. ------------------------------------------------------------------------------------------ Subject: ICOM R71A power supply fix From: “pierfelice” Date: 1997/12/13 Message-ID: <01bd0764$ed2e4b00$LocalHost@default> Newsgroups: rec.ham-radio,rec.radio.amateur.boatanchors,rec.radio.amateur.equipment,rec.radio.amateur.homebrew,rec.radio.shortwave [More Headers] My R71A had power supply trouble as many have had or will. The design of the supply results in poor regulation and AC ripple on the supply output. My solution was replacing the active components with one ECG1954 low dropout 12 Volt 1Amp 3 terminal regulator. The ECG1954 requires but 13 Volts at its input to function unlike other 3 terminal regulators that require about 16 Volts (such as the 7812). The ECG1954 is a TO220 case as was the original pass transistor Q1. Cost of the ECG1954 was $5. Basic steps I performed: 1) Remove the regulator unit from the radio. 2) Remove the PC board / transformer from the regulator unit frame. 3) Remove everything on the PC board except C11,L1,F4,D1,C3,C4,C5,C6,C7,C9,T1 4) Install the ECG1954 where Q1 used to reside. Note that the mica insulator is no longer necessary on the heat sink and can be removed for improved heat transfer. 5) You will have to jumper the input and output pins of the ECG1954 appropriately. Add a jumper from the cold end of the fuse to the ECG1954 input. Jumper from the ground side of C7 to the ECG1954 ground pin and jumper the ECG1954 output to the radio’s DC input. I removed J2/P2 from my radio. 6) I also glued a rubber grommet on top of T1 to contact the bottom cover and reduce vibration induced in the cover from T1’s field. 7) Put the radio back together. Note that this fix may not work with other than “bare bones” R71’s. Mine does not have the crystal heater, FM, remote or any other option. The radio uses almost 1 amp as is and radios with more options may require a second regulator. How does it work? Great! Even though the radio was designed to run at 13.6 Volts, mine runs fine at 12. No hum and stable down to 105 Volts line. I also installed an International Radio (WWW.QTH.COM/INRAD) Fox-Tango CW filter at the time of this modification and I am very happy with the filter’s performance. Bob, KB8TL -- pierfelice@NOTOSPAM.MCI2000.COM (Discard “NOTOSPAM” to reply) ------------------------------------------------------------------------------------------ mts@plix.com wrote: > > In article , > joemac@gto.net.om wrote: > > > > ICOM R71A Battery > > > > Hi, > > > > I have an R71E purchased about 10 years back and was expecting the same > > problem anytime. However, I have gone for the expensive option as I > > wanted the extra memories and VLF capability. > > > > I can't help you with a battery type and supplier but the way to change > > the battery is to carefully solder a small silicon diode to the > > positive rail of the backup battery (cathode to the rail). Then connect > > a similar voltage supply or battery (maybe a tad higher to take up the > > 0.7V drop in the diode) between the anode end and ground. This keeps > > the supply alive during the change and prevents the present battery > > from discharging through the backup supply. > > > > Making sure the supply is complete, desolder the existing battery with > > an iron that is not grounded, fit the new one, disconnect the diode > > and Bob's yer uncle. Actually, I think that you could get away with > > just removing the battery and quickly fitting another as the rail > > capacitance is probably good for a few microamps while you are > > beavering away. > > > > 73 de G3LLV, Joe > > Hello All: > > I do not recommend the above! > > I am so tired of everybody slamming the RAM card in ICOM radio's. I have > been repairing ICOM's since the RAM card was first used. I have 2 > radio's that use it, for 14 years now, still no problems. When the RAm > card came out NOBODY could offer the features at the price at that time! > > If you are worried, take a DMM, carefully measure the battery voltage, if > it is above 3v, STOP! you have nothing to worry about. Yes the cards do > fail very great once in awhile, but it is very rare. More common when > someone tries to replace the battery in the field. > > Yes, it can be done, but one little mistake or static surge to the card, > and call ICOM for a new one. It is just not worth worring about. > > If the card does fail order a new one, there cheaper than buying extra > memories you probably won't use or sending the radio to ICOM, it unplugs, > and the new one plugs in. How easy. > > Your NEW radio's use the same battery, what are you supposed to do when > it dies in 5 years! send the whole radio in. for a battery, at $75 hour > 1 hr min. NO THANK YOU. > > For those of you who have the RAM CARD, don't worry and enjoy your fine > ICOM radio! > > I welcome responses > > Scott Malcom > MTS ------------------------------------------------------------------------------------------ THE ICM1024 IS EASY TO INSTALL AND IT CAN BE USED AS A 32 CHANNEL DIRECT REPLACEMENT FOR ICOM'S EX-314 RAM UNIT. WHEN INSTALLED IN THE R71 or IC-751, THE 32 BANKS CAN BE ACCESSED DIRECTLY FROM THE RADIO'S FRONT PANEL WITHOUT ADDING PUSH BUTTONS OR SWITCHES. THE HEART OF THE ICM1024 IS A CUSTOM INTEGRATED CIRCUIT THAT HANDLES DATA AND BANK SWITCHING. (THE IC-745 REQUIRES EXTERNAL SWITCHES. ) HERE'S HOW IT WORKS BY CONNECTING THE ICM1024 RIBBON CABLE TO THE R71 MATRIX BOARD, THE MEMORY NUMBER (THAT'S DISPLAYED ON THE RADIOS FRONT PANEL) CAN BE USED TO CHANGE THE BANK NUMBER. WITH OR WITHOUT THE IC-EX310 SPEECH MODULE , THE SPEECH BUTTON ON YOUR R71 WILL SERVE AS A BANK=MEMORY SWITCH. TO RAPIDLY CHANGE BANKS, SIMPLY ROTATE THE MEMORY KNOB AND SELECT A MEMORY. THEN PRESS THE SPEECH BUTTON AND THE BANK, (THAT CORRESPONDS TO THE MEMORY NUMBER) WILL BE SELECTED. EACH TIME YOU PRESS THE SPEECH BUTTON ON THE IC-751, YOU STEP TO THE NEXT BANK. THE FUNCTION BUTTON REVERSES THE STEP DIRECTION AND THE XIT/RIT RESET BUTTON JUMPS YOU BACK TO BANK 1. THE IC-745 REQUIRES 3 EXTERNAL SWITCHS. BY PLACING A FREQUENCY (THAT CORRESPONDS TO A BANK) IN A MEMORY LOCATION, YOU CAN DETERMINE THE BANK NUMBER. FOR EXAMPLE, 2.2 MHz IN MEMORY 32 CAN INDICATE THAT BANK 22 WAS SELECTED. EXTENDED FREQUENCIES THE RECEIVE FREQUENCY LIMITS ROM WHERE MODIFIED AND NOW THE RADIO CAN TUNE FROM 10KHz TO 31 MHz. (MODELS IC-751, IC-751A, IC745 AND R71). HERE IN THE MIDWEST, FOR EXAMPLE, I CAN COPY RTTY ON 48 kHz, THE S.L.F.C.S. (Survivable Low Frequency Communications System) TRANSMITTING FROM SILVER CREEK NEBRASKA IN THE CLEAR! CONTACT; WILLCO ELECTRONICS, P.O. BOX 788, NEW LENOX, IL 60451. PHONE (815) 723-1874 JACK ALBERT WA9FVP I also have this email address: WILLCO788@aol.com -- Check out my web pages for radio (pirate, spy numbers) and Mac software. http://www.access.digex.net/~cps NOTICE: All email sent to this account is subject to public release. ------------------------------------------------------------------------------------------ Article: 17580 of rec.radio.shortwave Newsgroups: rec.radio.shortwave Date: Tue, 19 Jan 1993 16:36:33 EST Sender: Short Wave Listener's List From: "David L. Wilson" Subject: R-71A Memory Notes Lines: 25 I have heard that a new company named Willco is going to sell no fail memory for the Icom radios. Two models, one with 64 channels for around $70 and a 1000 memory channels for around $149 will replace the small battery backup unit. The Willco board will use standard AA batteries. When the batteries die in the Willco unit, the radio won't fail and need servicing as is now the case. (However, the memories would need to be re-programmed.) Using the lock button and memory switch, one steps through the banks of 32 channels each. One channel in each bank can be used to store the channel number for display to identify the bank number according to the maker. Willco's address is P.O. box 788 NewLenox Il. 60451 If someone orders one, let me know what you think of it. I am not sure which radios other than the R-71A in which it will work. -- David L. Wilson dwilson@s850.mwc.edu Department of Mathematics Phone: H (703)898-1084 W (703)899-4744 Mary Washington College Amateur callsign: AC4IU (ex-KD4ASW/KO4EQ) Fredericksburg, VA 22401 Lat./Long.: 38 15 40 N/ 77 32 51 W Copied from the QRZ! Windows Ham Radio CDROM ------------------------------------------------------------------------------------------ Willco Ram Board The information you require is (courtesy of Steve, WB7PSD) - Willco Electronics P.O. Box 788 New Lenox, IL USA 60451 Phone (815) 723-1874 Fax (815) 723-1436 Model # ICM1024B Icom No Fail Memory I have written to them and hope for a reply soon. 73 de Joe, G3LLV Airwork Limited Sultanate of Oman PART II When I had an R71a a few years ago, my battery went dead. The R71a does become an electronic vegatable. I bought one of the Willco units and it worked very well. It was a bit hard to install the ribbon cable, but then again my eyes and hands aren't as good as they used to be. I did get it working however. A previous append said you could just install the board and get 32 memories which is true. I used it that way till my 'attitude' was correct to install the 100 memory mod. ------------------------------------------------------------------------------------------