Aftermarket Stepper Motors for Icom IC-756 Auto-tuner

***NOTE*** Be sure to read the updates near the bottom of this piece. 

 

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. Adafruit sometimes has this motor in 1/16 ratio, other times 1/64. The 1/64 is smoother in the tuner, but either will work. Also, sometimes labeled as 5v, other times as 12v...I found it's the same motor resistance and the motors have a spec that states "5-12 vdc". 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!

 

UPDATE, 2/2/2019:

I got a message from Jim Durham, and wanted to add it in before I lost it. This is a link to a stepper with a 1/64 gearbox ratio, and seems to tune a bit more smoothly than the units I use. Mine are still working fine, but this looks like it might be a better choice. Here's the link:

https://www.amazon.com/Diymore-28BYJ-48-Valve-Stepper-Motor/dp/B01J3KV3B2/ref=sr_1_1?ie=UTF8&qid=1518217311&sr=8-1&keywords=stepper+motor+12+volt+4+phase


 

 UPDATE, 1/8/2022:

I found these on eBay and Amazon. Search for part # 28BYJ-48. Several vendors have these listed , some say 5v, other say 12v, it's the same stepper with a recommended operating boltage of 5-12 vdc. The 1/64 ratio is the better version.

 

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. If you damage something while trying this, don't blame me...these are only notes I've posted from several installations I've done, and feedback from others who have done the same. This is long, read it all. The new info and updates are near the bottom.

I've included connection info on displays I've previously used, as some are still floating around on eBay and such. The most current display I use is from Yuxian, described later.

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Winstar WG320240D-TMI-TZ# display (LONG LEAD TIME!): 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. ***NOTE*** I now pick up +5vdc for the back light from pin 12 on the cut board, and use an internal 5v regulator in the radio. The newer display back lights require only about 100 mA. No need to build another 5v reg circuit. 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 back light current. Open coil L103 along side of the HV compartment to shut the CCFL HV supply off when using displays with LED back lights. (I no longer disable the CCFL supply like this, much testing has proven the cfl supply to not be a significant noise source.)

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.

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

 ******************************************


(DISCONTINUED) 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) . This has been the easiest display to install to date, but availability seems to now be an issue...

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. No back light supply mods needed!

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 ??
 
******************************************

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.

*** Update*** Another person bought a New Haven NHD-320240WG-ATMI-TZ# display, and it was MUCH too wide. Avoid that model. Try to choose displays that have a max board width of around 142mm wide and 96mm tall (although board height isn't as critical)

******************************************

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...

******************************************

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.

******************************************

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. Use 28ga. insulated wire for the jumpers.

Cross ref for the Winstar Display

******************************************

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.

******************************************

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

******************************************

***UPDATE, 8/31/23***

Another model successfully fitted and installed was purchased from aliexpress.com as Yuxian model #
LG3202404BMDWH6N . This is the display I currently use in all 756 upfits. It was fitted and worked fine. It's board dimensions measure 139mm wide x 106mm tall. This is the only model I can still find available that works in these rigs properly. Use 28 ga. insulated wire for jumpers, it's much easier to solder to the pads on the "cut board". 

Attention: Apply +5vdc to the Yuxian display pin 6 (Vdd), ground to pin 7 (Vdd). Measure between pin 8 (Vout) and pin 7 (Vdd, gnd) to check for the presense of -22 to -30 vdc. If nothing, connect Vout to pin 8 on cut board. If negative voltage is present, leave pin 8 connection open. This scenario is an upredictable variable.

I no longer build a 5vdc supply, I power the backlight from 5vdc from the cut board, pins 11 & 12.

This is the wiring matrix between the "cut board" and the Yuxian display:
 

Cut board = New display

1 = 9

2 = 10

3 = 11

4 = 12

5 = 1

6 = 4

7 = 2 (latch)

8 = 3 (shift)

9 = 13

10 = Frame ground, internally jumpered to pin 7

11 = 7 & 16 (LEDk)

12 = 6 & 15 (LEDa)

13 = 8 via 2k resistor

14 = 5

******************************************
***UPDATE, TIPS, 2/9/2024***

Tip #1:  I've been meaning to add this tip. Sometimes, depending on the internal menu settings of the radio, the contract will be WAY off and look like a blank screen. I've installed these in radios where the radio screen was totally shot, so there was no way to set the contrast to 50% before starting (something I like to do). There is a contrast pot on the outer board in the sub-chassis, very near where the S-meter terminals solder in place, just behind the wide ribbon cable. If you boot and have only a blank screen,  use a plastic tool, radio ON, turn the pot back and forth to set the contrast as you like. Once all is working, I like to set the menu at 50%, turn the pot for perfect display, and let it go. That way, you'll have a nice range of adjustment from the menu.  NEXT, if you boot, adj the pot and still no font, go to Tip #2...

 

 Tip #2 : If still no font after tip #1, switch pin 2 & 3 on the display. I've found the mfg sometimes gets latch & shift reversed. Don't know why, but it happens :-)

******************************************
List of displays used:

- Stanley GMF32024ABTW1X (easiest fit to date)
- Yuxian LG3202404BMDWH6N (from aliexpress.com)
- Winstar WG320240D-TML-TZ#
- Winstar WG320240D-TMI-TZ#
- APlus Displays: AG320240D-TTI-TZ#- East Rising ERM320240SBS-1
- New Haven NHD-320240WG-BxTGH-VZ#-3VR (dimensional issues on some)
- New Haven NHD-320240WG-ATMI-TZ# (too big)

- Researching a Yuxian SP14N002 CCFL now, the CCFL backlight would make for an easier installation and use the OEM CCFL backlight driver. More on this later...


Dave WB4IUY
http://www.WB4IUY.net

Info on Icom IC-756 CI-V repair...

I made these repairs in September of 2013, but a post this morning from another ham with the same problem prompted me to dig up the info and post to hopefully help others with the same problem.

My Icom 756 (not pro model) lost it's CI-V port from energy induced into the CI-V cable during a near lightning strike. I've read where folks have found the problem to be the transistor pair q801 & q802. This is a buffer circuit on the CI-V port input on the rig, prior to the processor. I found them on the schematic and ordered those in. VERY cheap, only a couple of bucks. My problem was, I couldn't physically find them on the main unit board. All of the pdf's I found online are far too blurry to see the part...

I was referred to Scott Malcom at MTS. He was a tremendous source of help, and sent me a couple of pics of the main poard with the parts I was looking for, circled for my ease of location. Super nice guy, really knows these rigs, I'd recommend him for service if you need to send your rig somewhere for repairs.

I replaced q801 & q802. I tested all of the smd resistors in the circuit and found them to all be OK. Once I got the CI-V port transmitting data (nice TTL level data seen on a scope), I tried every possible combination of baud rate setting on the USB port, the rig, and the software...but nothing worked. I verified the rig address (50H), and everything was OK. Really had me scratching my head...I pulled the rig apart 4 times while testing voltages and ruling out problems, bit by bit.

I used a little breakout board and level converter I borrowed from a local ham friend, and went directly from the DB9 com1 port on the computer and could get things to talk. I had installed the drivers associated with the USB CI-V replacement cable I got from Kawamall (same folks the previous cable came from), but it would not talk, no matter what. I got an email from Clint W5CPT that directed me to this link for drivers:

http://www.miklor.com/COM/UV_Drivers.php

I found, running winXP, the drivers sent from Kawamall with the level adapter cable were a version that was not compatible. I downloaded ver 2.0.2.1 from the link Clint sent over, installed them, and all is now well.

Thanks for the help and feedback from everyone, especially Scott Malcom for assistance locating the transistors on the main PCB and answering several questions and giving his opinion, it helped me work my way through this process and get my rig up and running again.

I've uploaded the bits that might help someone else with a blown CI-V port like I have, and you can find them at:

http://www.wb4iuy.net/wb4iuy6e.htm

By the way, I use the ribless programming cable from Kawamall on eBay for my CI-V interface, instead of the Icom CT-17. It works on most all Icom rigs and only costs only about $20.Lastly, I'd recommend, when you disconnect your antennas for protection from an electrical storm. also unplug the CI-V cable from the rig :-)






Sincerely,
Dave WB4IUY
www.WB4IUY.net

W2ENY AM Filter for the IC-756

I've been looking for an AM filter for my IC-756 for many years, and just stumbled across a filter from W2ENY. I think he used to offer these, and went out of production for some number of years. He has brought a limited number of these back for sale. I emailed him, he replied almost immediately that he still had some, and I ordered one. I'm happy to have finally found one of these babies. I work AM from time to time on 160 thru 10, and usually operate one of my boatanchors due to the w-i-d-e passband on AM. His page is:

http://w2eny.com/6kc_filter/ I received the 6khz AM filter from W2ENY for my IC-756. The instructions were EASY to follow and the mod was quick and simple. I LOVE it! I've been working AM on 80, 40, and 15m with the 756 and have great selectivity on AM. I replaced the 15khz filter in the 455khz I.F., and have noticed no issues with working FM on 10m, listening to broadcast stations, etc. My 18 year old IC-756 is now perfect in my opinion, and everything is working great. This is the filter the rig should have come with from the factory, as all modes are well behaved, now.

UPDATE: 3/16/14... After using the filter for about a year, I felt the need to make another change. The instructions from W2ENY mentioned to replace the 15khz filter in the 455khz I.F. with the 6khz AM filter. I found, when operating AM on 10m, it is desirable to have access to the 15khz filter to open up 

the receiver a bit for the broadcast audio often heard on AM. Also, when working 10m FM, the 9khz filter in FM narrow is a bit too narrow for good audio and clipping would occur. I never found a need for the 9khz filter in AM or FM operation, but I constantly found the need for the 15khz filter. So, I reinstalled the 15mhz filter and installed the AM filter (6khz) in the place of the 9khz filter, and all is now well. Just my $01 worth, but it sure works out better at my QTH in this configuration. 

You can visit my website at www.WB4IUY.net for more mods for the IC-756 pre-Pro (analog) model, and lots of other ham radio stuff :-)  

Updated 60m Mods for the Icom IC-756

 60M for the IC-756 Standard

Modifying the ICOM IC-756 Standard (non-Pro model) for 60m takes a little work, but it's worth the effort. First, the transmitter has to be opened up for general coverage operation. That's pretty easy. Here's the info for the first phase of the modification...

Remove bottom cover. On the MAIN board you will see IF filters and a daughter board (DSP filter) on the right side. The W805 jumper and IC803 chip is located under the DSP board. You have to remove the DSP board (carefully) and look for the part labeled IC803 and the line of SMD jumpers (little green parts). Locate and unsolder the W805 jumper. Re-Install the DSP board and put the bottom cover back. Below is a drawing of the chip & jumper locations, a pic of the circuit board, and a pic of the jumper on my fingertip after removal.

                     ---------------
         [W801]     |               |
         [W802]     |               |
         [W803]     |    IC 803     |
         [W804]     |               |
REMOVE== [W805]     |     CHIP      |
         [W806]     |               |
         [W807]      ---------------
         [W808]

  

When I first modified the processor, as I had seen numerous bits around the web for adding 60m, it worked 'OK', but would only put out about 50% power on 60m. I found that the band matrix is setup to use the 80m low pass filter up to 6.0 mhz, where it transitions to the 40m filter. Another ham I was talking to on the internet had the IC-756 Pro II and modified his for 60m coverage as I did, and had the same problem with low output power. He had access to some filter design software, and modeled the 80m filter to see where the problem was. He came up with a few capacitor changes to alter the upper end of the filter response to fix the problem in the Pro II. I checked the manuals and board layouts against each other, and while the filter units in the standard and Pro II are physically a little different, the circuit was the same. I ripped mine apart tonight and dove in. Change C7, C66, & C69 to 180pF disc. Change C15 to a 270pF disc. This moves the knee of the filter from 5.25mhz to 5.6 mhz. The end result was awesome...full power right up to the edge of the 60m band and no purity issues. One of the pics here is the filter as modeled in software, the violet curve is before mods, the white curve is after mods. The other pic is of the filter unit.

One last note...the internal antenna tuner isn't mapped to work correctly on the 60m band, but the rig works great with an external antenna tuner or with a resonant antenna. Hope this helps some of you with your 756 to enjoy 60 meters. The filter mods will also work with the Pro II once you use the appropriate mod for general coverage transmit. Many thanks to W6FM for the filter model work!

73
Dave WB4IUY
www.WB4IUY.net

IC-756 Display fix and 60m added!

I bought my IC-756 back around '95. It has been a great radio, except that the display began to fail a few years ago and Icom would not support it. They came out with the Pro-series 756's, and had no displays for the repair of the $2500+ radio I bought in '95.




I continued to put up with the problem, and it continued to get worse and worse...to the point where I could almost not read the display and had to rely on HRD and a CI-V interface to read some functions and frequency on the computer in the shack.

In recent years, a ham Richard Rosenberger PA7FA in the Netherlands designed a replacement display for it. You can see his display kit at http://www.pa7fa.nl



I was about to send the front of my rig to him to have his new display kit installed (I couldn't possibly handle all the SMD soldering and such), when I got a message from Bob wa8ulw stating that he had an old 756 that had been struck by lightning and that it had a good display. Wow...was I ever relieved to hear this!

Bob and I worked the deal, the faceplate assembly from his 756 arrived at my doorsteps this morning, and it's already on the rig and looking good as new. While I was doing the work, I modified the 756 to add the use of the 60m ham band to it's range of transmit frequencies.

Check out the before and after pics, including the little SMD jumper I had to remove to allow transmission on the 60m band...

BEWARE...this isn't all you need to do to operate 60m on this rig. The bandpass filters don't operate correctly on 60m and will reflect a good bit of power back to the PA...could cause damage it you operate there much. I did a bit of work to fix that, see this info in my blog at: 

http://wb4iuy.blogspot.com/2014/03/updated-60m-mods-for-icom-ic-756.html


Dave WB4IUY
www.WB4IUY.net

Icom's lack of support...

Here's a $2800 IC-756 radio with a bad display. Icom recognized that it was an issue. Rather than support it, they recommend to BUY A NEW RIG from them to replace it. WTF???  There's lots of these out there, stuck with this problem. As much as I like this rig, i'll never spend another penny with Icom.
Dave Hockaday WB4IUY
AMA 119484
Live from my handheld...

Operating AM on Icom IC-756

I've tried using my IC-756 on AM from time to time, as I enjoy this mode on 75, 40, 20, and 10 meters. Unlike my Yaesu 901 and Heathkit equipment, the output power of my 756 Icom would drop considerably when I would modulate the transmitter with voice. In order to get decent power out, I would have to run my amp harder than I care when operating AM.

When operating at 25 watts carrier from my 756, I was producing about 25 watts pep when modulated at 100% (because the power output would drop to about 8 watts!). My amp (AL-82) would run about 350 watts carrier, and would fall back to about 85 watts or so when I would speak (still about 350 watts pep).

I built the little curcuit from W8JI's page this afternoon. I now operate the rig at about 10 watts carrier, which drives the amp to about 150 watts. When modulated the amp produces about 600 watts pep, but runs very cool.

Listening to it on my Yaesu 901, it seems much cleaner, but I can't hear any difference on my Heathkit SB-301. I guess this is partly determined by the detector used in the receiver of the receiving station. The amp is much happier, though, and runs much cooler. I can run a much higher PEP with a lot less heat!

I've posted info about it on my AM Mode page at:

http://www.wb4iuy.net/wb4iuy2l.htm