WB4IUY's Random Blog

I've been in Amateur Radio since 1974, and still find new and interesting things to do. I like to build, restore, and operate on the air. This is a blog of various info about my Ham Radio operations and activities, projects, and opinions. Visit www.WB4IUY.net for the lowdown at WB4IUY.

Monday, December 11, 2017

Aftermarket Stepper Motors for Icom IC-756 Auto-tuner

This may be old news, but just in case, here it is... I just repaired the auto-tuner in my IC-756 (not a pro version). One of the motors failed. I found a procedure online for repairing the motor, but also decided to try an aftermarket replacement motor. The OEM part number from Icom was MP28GA, and their new # for their replacements is MP24ZA. This happens to be the same replacement part used in some Yaesu auto-tuners, their part # is M2190023. The Icom part costs about $35 + shipping, the aftermarket part is $4.95 + shipping. Looks to be the same part, except that the aftermarket part has a brass output shaft vs. plastic on the OEM. 

This looks to be the same motor used in several Icom HF rigs as well as Yaesu.
I bought the aftermarket motor from https://www.adafruit.com , and it is their item #918 and cost $4.95 each. The plug is slightly different, but I was able to slice off a piece of the plastic clip from the socket on the tuner PC board and it snapped right on, but you could simply replace the connector from the original tuner motor...the wiring colors match perfectly. 

There's a great Youtube tutorial on how to repair the original stepper at:

http://youtu.be/UdY6RhNOCWg

 
 Comparison of back side of stepper motors...

 Comparison of front side of motors...

 
 Tuner is under this board...

 Board remove, exposing metal cover on tuner...

 Metal cover removed, stepper motors seen in lower RH side of pic. Remove screws from tuner, lift it up, loosen screws on motor coupling, and replace the motor. Very easy!
 




Dave WB4IUY
http://www.WB4IUY.net





Display Transplant into an Icom IC-756 (non-pro)


 Before...

 After!!

 The display has a more brilliant color than this, my phone cam just doesn't do it justice!



This blog is about replacing the LCD display in a Icom IC-756 classic. The displays in these radios haven't been supported by Icom in several years. This is an attempt to archive info & notes from myself and others about different displays used. I'll probably add to / edit this blog as I continue to test & install more displays.

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Winstar WG320240D-TMI-TZ# display: When installing this model, I had tried to drive the display contrast input (display pin 13) from the 756 contrast output (DV0, radio pin 1). It works, but over the period of an hour or so, one has to go into the radio menu and readjust the contrast setting. It seemed to be a thermal drift of some sort in that circuit. After working with the mfg, I discovered a few things:

1- The display generates it's own -25vdc and outputs it to pin display 12. The -30vdc from the radio pin 2 should not be connected to the display. The display is temperature compensated and it varies the -25vdc output at display pin 12 accordingly.

2- When driving display pin 13 from the radio, it ignores the display's temp compensation, thus causing the contrast "drift" or instability. Installing a linear potentiometer of 15k, high side to pin 12, low side to pin 14, and wiper to pin 13 allows the display contrast input to reference the temperature compensated internal -25vdc supply of the display, and I've found the contrast to be perfectly stable. Keep the pot as close to the display as possible, leads short...

3- I prefer to have the contrast adjustment where it can be easily reached, as contrast is somewhat subjective and based partially on the viewing angle. An internal pot is fine, but I like to be able to adjust it easily. I found the lower LH side of the cabinet (just below the handle) to be a good, easy-to-reach location for this. When mounting the pot somewhere that requires a few inches of wire to make the connection, install a 100pf capacitor across the high and low connections to the pot. The -25vdc output of the display acts like a nice antenna to radiate processor noise to the rest of your rig, and I found 100pf seems to be adequate to resolve the issue.

 
 100pf cap across high and low terminals of the remote contrast pot I installed in this radio...


4- Source a +12vdc switched point to build the 5vdc regulator for the LED back light. I use the point from the 4-pin rear panel  accessory port. Use a 7805 regulator and heat sink to chassis, and a 33 ohm 1/2 watt resistor in series with the output to the back light, to limit the backlight current. Open coil L103 along side of the HV compartment to shut the CCFL HV supply off when using displays with LED back lights.










5- If you plan to buy a Winstar display, try to locate the WG320240D-TML-TZ# instead of the WG320240D-TMI-TZ#, it is more easily viewed from above the radio.

6-  APlus Displays: AG320240D-TTI-TZ# seems to be the same as the Winstar display

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Stanley GMF32024ABTW1X: The Stanley display found by Rick K4PQ is by far the easiest to install electrically (no back light mods required and seems to be temp compensated in some other way) .

1- Contrast setting is very stable, the current requirement at display pin 13 is only a few MA (contributing to stability).  Connect the -30vdc supply from the radio to display pin 12 via 2k 1/2 watt resistor. Be sure to turn the trimmer down on the sub-logic board to about the 9 O'Clock position.


2- The back light is directly driven from the radio CCFL HV supply with no mods. This is not a polarized connection and polarity is not important.

3- This display has the best viewing angle of any of the displays I've tested / installed. It is viewed from above the radio easily, best of all the displays I've tested in this blog.

Can anyone find another source of the Stanley display GMF32024ABTW1X ??
 
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I'm waiting on a East Rising ERM320240SBS-1 to test now. It also looks like the New Haven NHD-320240WG-BxTGH-VZ#-3VR will work, but much more expensive.

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Folks have physically installed these various displays in the metal sub-chassis a number of ways from building brackets, re-drilling holes, etc. I prefer the Hot glue method recommended by Rick K4PQ...quick, easy, and very solid.

I use the Dremel tool to remove the little folded edge from the sub-chassis for best fitment...


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When disassembling the face of the radio from the sub-chassis, I've found cutting small cardboard tabs and inserting under the clips around the perimeter makes removal much easier.



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Using the original display as a donor, cut the plug for the ribbon cable and a piece of the board away, and stick it to the new board with thick double-side tape as a sort of "break-out" board to help with assembly. The numbers are backwards on the cut-away board from the actual ribbon cable and socket on the radio main board...makes no sense, but the cross reference chart takes this into consideration. Mark the ribbon cable TOP surfaces and make sure to not get the cable reversed during re-assembly.








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When removing the front panel from the sub-chassis, slip the rubber cover off of the main VFO knob, loosen the set screw found below it, and remove the long silver screw from the VFO brake.




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When removing the sub-logic board, be sure to unsolder the S-Meter connections to allow the boards to separate.


Dave WB4IUY
http://www.WB4IUY.net














Sunday, November 26, 2017

Antenna work - 11/26/17

Finally had a little time to get back on my tower and get more antennas pulled up. I broke my Force-12 6 element HF yagi into 3 sections, pulled it up the tower, and reassembled it from up top. The assembly went well and it was an easy one-man job. Once in place, I got the feed line and rotator cable pulled up and connected. Here's a few pics from the work...

 A shot down the tower as I pulled up part of the yagi...


 Looking south at the reflectors...


 Looking north at the driven elements...


 Looking at the horizon to the west from about 105' up...


 A pic from the front yard, the yagi sits at about 105' up now...


 Looking north, over the boom, cam at about 107'...


 Looking down the tower, my feet are perched on the rotator plate...



 The view to the west is awesome from this height...


 Looking up from my driveway, things are beginning to come back together, finally.


 Looking up from the northern part of my front yard...



Time to build the next antenna for the stack and get it in position #2!


Dave WB4IUY
http://www.WB4IUY.net












Sunday, November 12, 2017

Antenna work - 11/12/17

I completed my HF yagi today, for installation on the rebuilt tower. For those who don't know, my tower of 23 years was torn down in a storm in April 2016, destroying all of the 17 antennas that had served me well for all those years. Everything from the vertical that had it's tip at 138' up, right on down to the lowest antennas that were only 30' up. In addition to storm damage to the house and workshop, the tower and antennas system created such a mess that I had to rent a crane / man lift to get it all down from the surrounding trees and untangle / remove the mess of tower that loomed over our home. You can see the system as it was before the storm on my website at www.wb4iuy.net , mouse over the [WB4IUY] in the toolbar at the top, and click on [Antennas] in the dropdown that appears. 

Today I completed the feed harness for the driven elements, built and installed a new RF current choke on the boom, and tuned this 6 element Force-12 HF yagi. I got this antenna used for a great price...it's a $1200+ antenna that I otherwise would have never bought, it just needed a little TLC to bring it back to life. It is a trapless design, perfect for operating with high power. 

If all holds well, it'll be going up on the tower next weekend, and I'll start the rebuild of the next antenna for installation. I can't wait to get this baby in operation!

 RF Choke wound from RG-214 and attached to the boom.


 Bottom view, coax attached and jumpers installed between driven elements...


 Side view, feedline attached and jumpers in place between driven elements...


 Shack side of RF choke feed strapped to the boom...





 Antenna tuned on 10m, had to shorten the elements, drill, and re-rivet to set length...


  Antenna tuned on 20m, lengthened the linear loads a little to move the sweet spot down the band a little...


  Antenna tuned on 15m, had to lengthen the elements, drill, and re-rivet to set length...


 Antenna analyzer connected for testing...


 15m elements lengthened a little...


 10m elements shortened a little to move the sweet spot up the band a bit...

Dave WB4IUY
http://www.WB4IUY.net









MFJ-259 Antenna Analyzer Repairs...

I pulled out my MFJ-259 antenna analyzer to start tuning my Force-12 antenna, and discovered that it had a problem... It would not operate on the last 2 bands (lowest frequency ranges). Upon inspection of the internals, I discovered a battery had leaked acid on the main PCB and caused some damage. I washed the board with electronics cleaner and windex to remove oils from the cleaner, scrubbed it with a brass brush, and blew out the excess liquid with canned dry air. Acid had leached into the L2 (a 7.8uH inductor) and damaged it, it was electrically open. I poked around in my bins and found an inductor that was close in value, and installed it on the trace side of the board. This brought the lower bands back to life and restored the operation of the antenna analyzer.

The little hole in the PCB in the middle of that exposed copper area (seen in the photo), leads directly into the adjustable 7.8uH coil. I was able to get close in value with a fixed value coil, and the oscillator covers about the same range it did before the damage. At first I feared that the band switch was contaminated, but it was fine. The frequency range is controlled by a string of adjustable coils, all in series. The band switch shunts around them, so for lower frequencies, more coils are in the path and increases the inductance of the string. That one coil was open, so it wouldn't oscillate in the two bands controlled by it and the next series coil to the right. I was lucky that was all the issue was.


The schematic seen in the following pictures is also on my website at http://www.WB4IUY.net , mouse over [WORKSHOP] in the menu at the top of the page, then click on [SCHEMATICS MANUALs] in the drop down that appears. 

The analyzer was dead on the 2 lowest frequency ranges...


The PCB, after cleaning and scrubbing with a brass brush...


The fixed value coil I installed on the back side of the PCB. I slipped a piece of cardboard between the coil and the PCB to prevent possible contact between the coil and PCB traces / solder joints.


Yipee!!! Back up and running...


I connected the output to the bench counter, just to verify the VFO. 


 This schematic is also on my website at http://www.WB4IUY.net , mouse over [WORKSHOP] in the menu at the top of the page, then click on [SCHEMATICS MANUALs] in the drop down that appears. 


Dave WB4IUY
http://www.WB4IUY.net






 

Antenna work - 11/11/17

I picked up this Force-12 6 element HF yagi right after my tower came down in the storm of April 2016. Being a used antenna, there were a few things I needed to do before installation. After sorting through things, I decided to modify the boom mount to best suit my installation, and split the boom into 3 pieces to allow for re-assembly from the top of the tower, as opposed to hauling the entire fully assembled antenna to the top. All bits are now assembled and installed on a temporary tower section, and ready for tuning.

Some of the parts laid out, prior to assembly...


Boom mounting plate on my old manual mill, about to be modified for best installation on my mast...


Awaiting surgery...


Drilled, milled, and ready to go...


Mocked up with some new hardware...


Modified mounting plate attached to the boom plate, ready for installation...



Mid-section of the boom bolted to a temporary tower section I stood up in the back yard for assembly of the antenna and testing, prior to being hauled up the big tower.


A shot down the boom after fitting all boom parts together...


Another look at the boom, assembled, from an angle...


20m Reflector installed...


20m driven element now installed...


All elements installed, and ready for the feed harness...

Dave WB4IUY