WB0SMX

  TS-430 RF and IF Signal Paths Filed in Vintage Radio on Dec.28, 2016 I’ve had some questions from readers about where to obtain the color annotated schematics for the TS-430 that I used in some of my previous posts.   Violet line indicates the missing SSW signal. I created the schematics from a photo of the corresponding pages from the service manual for the rig. After taking a photo with my digital camera, I used the SnagIt program on my computer to add color lines representing the various RF, IF and Oscillator paths. Some of the other paths (voltages and such) were already annotated in red on the original schematics in the service manual. Anyway, here are the annotated schematics for the RF and IF sections, which were the only ones that I modified in this way. Enjoy… RF_Unit IF_Unit

  8640b Power Supply Repair Filed in 8640b on Nov.02, 2016 Early in the repair cycle of the 8640b, when I had just finished the brass gearset installation, I ran into a problem during the first power up after reinstallation of the deviation and range module. When I powered up the unit, I saw a flash from under the main board, and the unit came up with no led frequency display. I suspected that I had lost one of the power supplies. After finding the manual for the generator, I saw that there were 3 power supply boards with led indicators on them to indicate the various voltages were being generated.   5v indicator I found that the 5v indicator was not lit. Looking at the schematic of the board, I tracked down that it should have some relatively high voltage DC coming in on pins 15 and 9 of the module ( or pins 1 & 2 of the rectifier module). It had nothing coming in. I saw in the schematic that it was fed from a rectifier board. Since this had easy access, I...

  8640b Fine Tune Repair Filed in 8640b on Nov.01, 2016 Another item on the 8640b refurbishment project was the broken Fine Tune control. I could rotate the control from the front panel, but it had no effect on the frequency generated. After removing the bottom cover, I could see the problem. The Oscillator Module was missing the shaft that connected the fine tube knob with the control on the rear of the main oscillator   Shaft missing The shaft should be near the top of the picture above. I started the repair by removing the Main and fine tune knobs.   Main and Fine Tune controls     Knobs removed There is a module beside the main oscillator that needs to be removed, as it is connected to the wires from the back of the main oscillator. I just removed the two nuts/washers securing it, and pulled it up out of its card slot (it has an edge card connector). Then, it will lift out with the rest of the main oscillator module.   Loose module Next, I...

  8640b FM Deviation Pot Repair Filed in 8640b , Test Equipment on Oct.17, 2016 After replacing the gearset in my 8640b signal generator, the next item on the list was to repair the FM Deviation potentiometer, which had the shaft broken off where the knob would attach to the front. Since the pot is still electrically good, and I cannot locate another pot with the same value and length of control shaft, I thought that I could somehow repair the shaft. My first attempt at this was to remove the old shaft at the potentiometer body, and replace it with a longer one. It looked like I could remove the retaining clip near the pot’s body, and perhaps the shaft would pull out. Unfortunately, after removing the retainer clip, the shaft remained held to the body, so that did not pan out.   FM Deviation potentiometer I put the retainer clip back on the shaft and proceeded with Plan B. Plan B was to add a section of 1/8″ rod to the front of the shaft, using some mechanical f...

  HP 8640b Signal Generator Gear Set Replacement Filed in Test Equipment on Oct.09, 2016 Back in April of 2016, I bid on a Hewlett Packard 8640b signal generator to upgrade my test bench at home. This was from a local seller, and I won the bid for $115.00 + $20.00 shipping, for a total of $135.00. I figured for that price, I couldn’t go wrong. In working condition, these typically run about $500.00, depending on condition. When the unit arrived, it was not packed great (they used packing peanuts, instead of snug foam), but it was double boxed, and there appeared to be no damage in shipping. I plugged in the unit and brought it up slowly on the variac, in case there were shorts that might cause further problems in the unit.  To my surprise, the unit came up and appeared to mostly work. I could not turn the FM Deviation knob through all of it’s ranges, and the generator indicated that the deviation was out of allowed limits when I turned the FM modulation on. Al...