SG-230 Smartuner (Antenna coupler) investigation

I am fortunate that I have in my possession an SG-230 Smartuner remote automatic antenna coupler. This unit is capable of “tuning” a wide variety of antenna configurations from 1.6 to 30 MHz at power levels between 3 to 200W (PEP) and 80W (Continuous). Contrary to my usual method of operating, I took a moment to read the entire manual cover-to-cover. A summary of some of the specifications can be found in a comparison brochure which SGC provides. By the way, SGC provides a great deal of useful information such as an HF guidebook – lots of great information to be found!

SG-230 mainboard showing top layer of board and bodge wire near CPU
SG-230 mainboard showing top layer of board and bodge wire near CPU

Although, this unit is a few years old, it should certainly meet my goals. My intermediate-term goal is to use this coupler to allow the use of random long-wire antenna systems while camping. My present goal is to press the unit into service as a long-wire loop antenna coupler for an attic installation. As the SG-230 comes to be as a status-unknown unit, I wanted to bench-test the antenna coupler prior to deploying it in a difficult to access location. I started by having a look under the clam-shell to perform a sniff-test and to look for any signs of abuse.

SG-230 CPU version 1.03 dated July 2006 and bodge wire visible
SG-230 CPU version 1.03 dated July 2006 and bodge wire visible

Lo-and-behold, a bodge wire jumps out at me right away. The wire runs between pin-9 of a 74F74 and pin-1 of a 74HC393D. Investigating a little further, it looks like a rather shoddily done bodge at that! I really hope this was not done by SGC themselves; the quality of work on this is pretty poor, and the work was not cleaned either.

I took pictures so that I could later refer to the images for settings such as jumpers, CPU version, etc. I am glad I took these photos to better document this investigation.

Now there are many reasons to run a bodge-wire, namely when a problem in a design is identified and it is not practical to spin-up a new board immediately. This would likely have been fixed in subsequent designs, were it an actual design issue. When a bodge wire is found in a relatively simple design, it may be beneficial to investigate a bit further. Was this a repair? or a design re-work?

74F74 Dual D-Type Positive Edge-Triggered Flip-Flop pinout
74F74 Dual D-Type Positive Edge-Triggered Flip-Flop pinout

Never the less, let’s dive into the details. What exactly are the devices and does it make sens to have run the bodge wire the way that they have? Referring to the datasheets for the 74F74, we discover that this IC is a dual d-type positive edge-triggered flip-flop. This is likely used to convert an analog waveform to a digital fast-edge binary waveform for frequency measurement. It is likely that the output of this flip-flop goes to a counter or a buffer. The 74HC393D turns out to be a high speed CMOS 4-bit binary counter.

74HC393D high speed CMOS 4-bit binary counter pinout
74HC393D high speed CMOS 4-bit binary counter pin-out

Looking at the pin-out of each IC, it is apparent that the CK1 pin and Q2 pins are tied together and this makes sense for converting an analog waveform and then counting the resulting signal. It may be worth probing the traces between the two IC pads to see what the issue is/was. It may be that there is no electrical connection between the pins on the board (layout issues, forgotten pads, etc) or it may be that there is a compromise of some kind which negatively impacts the operation of this (supposed) frequency counter circuit. To really dig into this, I would need to remove both ICs to probe the pads properly. I would also be interested to know if as part of the bodge, they “lifted” either of the pins to isolate them from the PCB. So many questions!

Detailed view of bodge wire between 74F74 (Dual D-Type Positive Edge-Triggered Flip-Flop) and 74HC393D (high speed CMOS 4-bit binary counter)
Detailed view of bodge wire between 74F74 (Dual D-Type Positive Edge-Triggered Flip-Flop) and 74HC393D (high speed CMOS 4-bit binary counter)

Also note that there appears to be a (deliberate) solder bridge on pin 14 (Vcc) of the 74HC393D to a near-by SMD resistor. Using pin-14 of the 74F74, I was able to ascertain that the solder bridge to pin-14 of the 74HC393D makes sense to provide a Vcc source to the IC through the common PCB trace wire running vertically along side the two ICs.

My question here is: was this an intentional solder-bridge or an accident? My guess is that someone goofed on this portion of the circuit design, requiring two bodges in this PCB version. If anyone out there has an SG-230, I would be VERY curious to know if you have a similar bodge as I found. Please let me know if you can!

Being fairly confident that the bodges found would not negatively impact the operation of the antenna coupler, and with no other evidence found in a quick sniff and poke of the board, I powered the unit (observing the correct polarity, which apparently has been an issue for some users). Brief testing yielded no magic smoke being let-out and what appeared to be good function of the unit. Time to install it in my attic! If ever you run into issues with one of these units, SGC put out a troubleshooting guide to refer to; I can really get behind a company that demonstrates the right-to-repair.

One last note, with HF radios which “fold-back” power during SWR mis-match, sometimes an antenna tuner or (in this case) coupler is not able to find a match due to the low input power. It may be necessary to increase the power output during high SWR events. Here is a description of how to accomplish this task on a Yaesu FT817.

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10 Responses to SG-230 Smartuner (Antenna coupler) investigation

  1. it is old information but interesting to read
    Thanks for sharing your investigation of the SGC-230
    The one I have is destroyed someone did connect the 14V DC to the mains..
    is it possible to get the CPU or firmware for this SGC tuner?
    Otherwise it is the end … and only its case can be used for an other tuner..

  2. I got tuner from some ham who put 230VAC on the 14VDC terminals
    fuse exploded unfortunate there is no voltage protection like a simple suppressor ..
    then this tune would still be alive..

    Does someone has a programmed CPU MC 68HC711E9 or the firmware for it?
    If so the thing could be reparable …

  3. Reda says:

    J’ai acheté un SG-230 dernièrement et j’ai branché le fil rouge et le fil noir avec une alimentation de pc (12v/10A) avec mon iCOM ic-78 , mais le problème c’est que”on je fais de TX j’écoute rien de la par de smartuner SG, Y-a-t-il quelqu’un qui m’offre une solution ?
    Merci et 73 QRO.

  4. Ken Taylor says:

    Hi James,

    Hope you don’t mind me contacting you. I purchased a SG-230 some years ago second hand from a former club member. It has given great service except for one thing, it will not tune on the 12m band, it doesn’t even try. I borrowed a FT-857 that had been modified to open the transmit range and I found the the tuner was dead either side of 27MHz so I assumed it was an anti-CB mod. Anyway, I have it opened up on the bench at the moment as I’m troubleshooting another problem (probably not the SG230 – cabling) and I notice there are a couple of jumpers not identified on the PCB and wondered if they had anything to do with the 12m band problem. Before I tried I thought I’d check the Web to see if there were any experts out there and came across your site. My setup is a TS-590s and Inverted L antenna.

    The label on the processor chip says 1.01 Jan 2000 and there are no bodge wires visible. I see some jumpers on the schematic but could not find any explanation of them.

    Any ideas?
    Thanks for your time.
    Ken M1SLH

  5. Dale says:

    That wire is not from the factory. It looks like that 74F74 has been replaced by hand judging by

    The trace on the PCB runs from Pin 9 on the 74F74 to Pin 1 on the 74HC393.

    I’ve owned/repaired a few SGC tuners of different models.

    I had a “Working” one I won on eBay on the bench this week and someone had been messing with it previously and this had 2 transistors in the RF sense path instead of diodes, so I replaced all the SOT23 1N4148s with BAS21 diodes. That sorted the RF sense but I was having trouble tuning certain frequencies. I replaced the 74F17, 74F74 and the 74HC393 which didn’t resolve it. It seemed to be a counting issue. Mine had a factory installed resistor from Pin 11 on the 74F74 to Pin 1 on the 74HC393 (Pin 1 was lifted) this was causing a divide by 2 instead of 4. So I removed the resistor and put Pin 1 back to Pin 9 and it’s working perfectly. I can only assume a track got damaged on yours when the 74F74 was replaced.

    Dale – 2W0ODS

    • Dale says:

      Made a slight error on what I wrote, it should be Divide by 2 (Not 4) the second output acts as a buffer on the 74F74, but that was bypassed and the output attenuated with the resistor for some strange reason.

      I’ll email you a picture of the “Resistor Mod” which I had removed, I wonder if yours had that originally and your 74F74 was removed by mistake when the fault was just down to having the cascaded output disabled and a limited output to the 74HC393.

  6. Gerd Richter DJ5IW says:

    Hi James,
    sorry abt the late replay. Enclosed a picture of my unit. I found the failure. The Microprocessor is defect. I had an other proc. from an friend and this works with my hardware. Where can i get a processor. Do you know a source. The mails to SGC coming back as not deliveriable.
    The picture is sent to your email account.
    73 Gerd

    • James says:

      Thank you for sending the image as a comparison!! Looking quickly, it appears that there is a nasty solder-bridge between pins 8 & 9 on IC 2 (74HC393D) which lands on pin functions 2QD and 2QC respectively. This may impair the unit’s function; I haven’t looked at the schematic.

      So as I understand it, you need the main CPU for this unit? A direct replacement may be available on eBay or similar sites if Digikey, Mouser and the usual suspects have no stock. If there is any program code in the CPU, you may have another small problem there too; though it looks like the program resides in an EPPROM.

  7. Gerd Richter says:

    Hi, thanks for this very good information abt. the SG-230. On you photos I saw your processor has the Version 1.03. I have an older one 1.01. Where can I get an update.
    73 Gerd DJ5IW

    • James says:

      Hi Gerd,

      No problem at all! I am glad that the information has been useful to you. I will look around a bit to see if I can help source v1.03 of the processor for you. I imagine that it is possible; provided that there were no hardware changes between the different CPU versions being deployed.

      I am curious, does your PCB have the same “bodge wire” as mine does?


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