From: http://homepages.ihug.com.au/~vk5vka/draklist.htm Is it true that later versions of the R8B tune down to 10 Kilohertz? Yes the newer R8B's came with a revised ROM chip that allows the CPU to tune down to 10 Khz. However, the front-end of the receiver doesn't have a dedicated bandpass filter (BPF) for the VLF range. There is considerable attenuation below 100 Khz because of this and performance is not what it could be. How do I find out when my Drake R8B was made? The first digit in the serial number represents the year, 9 = 1999, 0 = 2000, 1 = 2001, etc. The second digit is a letter and represents the month, A = January, B = February, C = March, etc. The next four letters represent the model number. The last four digits are the unique serial number of that particular unit. ========== R8B Backlight Modifications The following article was written by J. W. Schermerhorn. Here's a description of the R8B "backlight mod" that I did using four bright white LED's. Note: 'R' = Remove 1. R- Front panel knobs. (set screws) The original R8 uses a set screw on the metal tuning knob. The A&B model tuning knobs are plastic and pull off. It can be hard to do if it's never been off before. 2. R- Front panel (black) with clear display window. (screws on top & bottom of panel) 3. R- Metal panel that holds two keypad membranes in place on their contact boards. (several screws) Set the keypads aside. 4. R- Front chassis frame from main frame. (two screws on each end) Pull the front chassis forward from the main frame for better access. Don't stretch the connecting wires too much. 5. R- Multi-wire (blue) connector from the back side of the LED PCB. (PCB means Printed Circuit Board) 6. R- LCD display mounting screws on front chassis. (four screws, two on each end of the LCD) This is why you had to remove the metal frame that covers the keypad membranes. The two LCD screws on the right are not accessible with the keypad frame in place. If you want to make it easier to remove these LCD screws again, cut two semi-circular notches in the keypad frame where it covers the two LCD screw heads. I did it with my "Dremel" tool using a metal milling bit. You won't have to remove the keypad frame again to access the right pair of LCD mounting screws. Carefully remove the LCD with the LED backlight PCB still attached, from the front chassis frame. There may be a screw near the S-meter to remove. 7. R- Six screws that hold the LED-PCB to the off/white plastic LCD frame. Keep your fingers clean so you don't contaminate the contacts on the LCD side of the LED-PCB. You now have the LCD assembly with it's rear plastic frame ready to install the white LED's. I used part # 900-7863 from the "Radio Shack.com" catalog. These are bright white 3-mm dia./ 4.0-V/ 20-ma/LED's. You need four of them at US$3.49 ea. I installed two white LED's in each end of the LCD plastic frame. Space each pair about 1.5-cm apart and a few "mm" above the rear surface of the LCD. Drill the appropriate size holes for a snug fit so they won't move around in the frame. The LCD plastic frame material is quite soft. Don't push the LED's too far into their holes. If they protrude on the inner surface of the frame, it might make the light uneven behind the LCD. I had to reposition two of them to eliminate a "spotlight" effect. Make sure you don't lose the piece of white cloth material behind the LCD. It's there to diffuse the backlighting. Now you have to decide on how to power the white LED's. I used the 5.0-V DC supply line on the LED board that can be tapped at pin #12 of the blue connector that you removed from the rear of the LED-PCB. If you use a 5.0-V source with the white LED's that I used, it will require a current limiting resistor of about 150 ohms in series with one lead of each LED. The remaining leads must go to a ground point on the PCB. The disadvantage of using pin-12 on the LED PCB is that it's always powered, even when the receiver is off, so the backlight is always on. I got around this by installing a small 12.0-V relay to control the 5.0-V line. The relay is powered by the 11-16V *switched* source from the power supply. Since this voltage source is turned off by another factory installed relay on the power supply PCB, the 5.0-V line to the white LED's will be turned off by the relay I added. There are other possibilities for powering the white LED's, including using the 11-16V source mentioned above. There is also a 10.0-V switched source available at the power supply. Either of these sources will require larger value current limiting resistors to keep the voltage/current within specs for the LED's. Ohms law at work! Using white LED's will produce a display with white characters on a blue-green background. The blue-green color is apparently intrinsic to the physical structure of the LCD material. It may also pick up a little green from the PCB behind it. I find the new backlight more pleasing than the "drab" OEM green. I think the characters have better definition too. You could experiment with putting a colour filter in front of the LCD or try bright blue, red or orange LED's too. Of course you have to turn off the original green LED's on the backlight PCB. I simply clipped them off the board with a snipper tool. If that sounds too "final" for you, you'll have to get into the schematic to figure out how to remove the power from the green display LED's (56 of them) without losing the six behind the S-meter. I decided it wasn't worth the effort. I also think the white backlighting works better if the green ones are removed. Their presence might add some green to the white light. I left the six behind the S-meter. Actually, I had already changed those six to regular yellow LED's a while ago. Be careful when reinstalling the backlight PCB to the rear of the LCD frame that you keep the (many) LCD control contacts clean. This is important so all the character segments of the LCD will work properly. I cleaned the contacts on the PCB with some alcohol just to be sure. You should also be careful not to contaminate the two "Zebra" strips that are embedded in the rear edges of the LCD frame where it makes contact with the LED-PCB. The strips look like a sandwiched layer of black between two pink layers. The material is spongy. These strips transfer the control signals between the PCB contacts and the rear of the LCD. After reading the above, I can imagine that some of you may be thinking I have too much time on my hands! I've always enjoyed "improving" my receivers over the years. It started with a Hallicrafters S20-R. When I got done with it, the circuitry was unrecognizable from the original design but the performance was greatly improved. I bought another S20-R for parts so I could restore the first to OEM condition. I guess it raises the question of how much you can change a receiver and still have the original item. ========== Keypad buttons on my R8A don't work well. Any suggestions? To change or clean the keypad button assemblies, you have to remove all the front knobs and then the outer front (black) panel. This will expose the inner front panel frame. Each area of buttons is a rubber membrane which is held in place by a metal frame with screws around it. Remove each frame and take out the key membranes. Wash them carefully with a "soft" brush (no abrasives) in distilled water with a little liquid detergent. Be sure to clean/brush the electrical contact area on the backside of each key button. Rinse the membranes in distilled water several times and let them air dry. While you have the key membranes removed, you should clean the gold colored contact traces on the printed circuit boards where each key touches them. Use some 91% isopropyl alcohol on a "Q" tip swab. Don't rub the contact traces too hard. This is a project you can do if you're confident about working on electronic equipment, otherwise let Drake do it. The Drake part number for the 31-button key membrane kit is 2055191 Can my Drake R8A/B Tuning knob be improved? It's too light! The knob can be removed by pulling it towards you firmly. Some ways of making it heavier include the following. Fill the hollow back of the R8A/B knob with a mixture of epoxy (slow curing) and steel ball bearing's. It creates a smoother feel because of the increased mass/momentum. This doesn't put any significant stress on the rotary encoder because it's supported at the rear (behind the encoder wheel) in addition to the shaft in front. I haven't noticed any wear/looseness since I weighted the knob several years ago. Another suggestion includes using the tuning knob from an Icom IC-R72 which apparently fits very well and is ideally weighted. The frequency hops/jumps on my R8B when using Main Tuning knob! Is there a fix for this? The problem is very likely the tuning encoder wheel which is on the opposite end of the tuning knob shaft inside the front panel. The only reliable way to fix this is to replace the encoder. It is possible to clean it with some electronic spray like "DeOxIt" but it's very difficult to get the spray inside the encoder without taking it apart and (you guessed it) it's not made to be disassembled. It's also possible that the contact "fingers" of the encoder wheel assembly have become misaligned. In that case cleaning won't correct the problem. You can order just the encoder wheel assembly without it's PC board, which is not really needed. The part # is 3260012. It costs about $US12.00. Contact the Drake service department for it. Installing the new encoder assembly is not too difficult if you know how to solder well and are not timid about removing the covers and front panel of the radio. It begins with removing all of the front panel knobs. The small ones have set screws. The big tuning knob pulls off. Remove the top and bottom covers of the radio along with the front (black) panel. This exposes the inner front chassis panel. Unscrew the hex nut that holds the tuning shaft/encoder assembly to the front chassis. This will allow you to remove the encoder with it's PC board from the rear of the front chassis. You must also unplug the three wire connector that runs from the encoder PC board to one of the radio's main PC boards. Now you're ready to prepare the new encoder for installation. Since you're not going to use the old encoder PC board, you must unsolder the three wires from that board and resolder them to the three matching terminals of the new encoder assembly which doesn't have a PC board. Put the new encoder shaft through the front chassis hole where the old one was and secure it with the hex nut. Plug the encoder wiring connector back on the main PC board. Reinstall the front (black) panel, top and bottom covers and all the knobs. ========== Drake R8 Modifications by DL7MAJ 1) Improve the tone control for a better bass response. 2) Backup Battery for the internal clock. 3) Reduce power consumption when the R8 is switched off. 4) Notch Circuit and hints for better alignment for better notch depth.