MFJ-9200 Technical Manual now avaliable

Discussion in 'Survival Communications' started by DKR, Oct 28, 2015.

  1. DKR

    DKR Raconteur of the first stripe

    In my earlier review of the MFJ-9200, I pointed out that the rig didn't have any kind of 'technical' manual - something with data useful for fixing the radio after the radio is out of warranty.

    So, I wrote a manual. I am giving copies of this manual to 9200 owners - gratis.

    Edit to Add - thanks to Steve Weber (KD1JV, the QRP guru) I now have a good schematic of the rig to send along with any manual requests.

    I want to note that Steve Pan at MFJ was very supportive, even to the point donating a dead 9200 for me to tear into for the photo work. I wish more manufacturers in the ham business were this supportive. All live testing was confirmed on my working 9200.

    These are the new "golden years" of ham radio, with newly licensed operators swelling the ranks daily. One thing I have noticed is that a significant number of these new hams have no background in radio/electronics. Thanks to the Internet and many sites that provide a focus on passing the Amateur service FCC tests, these new hams have a license but no real knowledge of how the technology works.

    I don't say this like it's a bad thing, because it is not. What it does mean is that a large number of folks entering this hobby have no clue on how to perform basic troubleshooting or repair on the radios they use in enjoying the hobby. To be honest, some of the newer radios on the market, especially handheld V/UHF rigs are, frankly, disposable. It has become, quite literally, less expensive to purchase a replacement radio than to attempt repairs via a commercial shop.

    On the other end of this equation, is the MFJ-9200. The radio is an excellent little HF rig and offers quite a lot to the portable operator. It is, to me, the ultimate in a Plug and Play rig. Add power, a resonant antenna, a set of cans, a key and you have a working multi-band HF station. Set the frequency, and you're on the air. Unfortunately, in my research prior to purchasing this radio, I discovered that technical data for the rig has not been made publicly available.

    This situation is a common issue with many radios imported to North America. Repair of the unit becomes problematic for a new or inexperienced operator and even experienced hams need at least some technical data and a parts list prior to attempting a repair.

    Rather than view this situation as a reason to avoid the purchase, I saw an opportunity.

    I wrote this manual for the new ham trying to fix what are most likely problems with a dead radio, quite literally, on the kitchen table with minimal equipment. The Manual covers the most common items that might need repair in the lifetime of the rig. I performed all of the testing on my own kitchen table.

    Here is what is in the manual....

    1. How to Use this Guide
    • Recommended tools and Test equipment:
    Describes minimum tools & test equipment required to use this manual.

    2. Warnings page

    3. Basic radio overview / Concept of Operations:
    3.1. Radio Overview.
    3.2. DC power busses and protection
    3.3. Voltage regulation
    3.4. DDS VFO sub-system
    3.5. Band Module diagram and header pin-outs
    3.6. Receiver
    3.6.1. Signal path.
    3.6.2. Filtering scheme.
    3.6.3. Audio amplification path.

    3.7. Transmitter
    3.7.1. Signal path.
    3.7.2. SWR protection for final amplifier.

    4. Troubleshooting Basic Radio Problems:
    4.1. Radio does not turn on.
    4.2. No received signal is heard.
    4.3. No RF output/Low RF output
    4.4. No or low audio output
    4.5. Radio doesn't key or keys erratically
    4.6. Display is dead, displays "funny characters" or has no backlight
    4.7. Radio is off frequency (display doesn't match measured output signal)

    5. Sub-system or specific component Tests
    5.1. DDS function
    5.2. 60 MHz Master Clock
    5.3. Adjust VR for +5VDC
    5.4. BFO function
    5.5. First Mixer
    5.6. Second Mixer
    5.7. Audio Path
    5.8. Phones jack
    5.9. Bypass Band Module
    5.10. Test Q10 with Ohm meter

    Basic Maintenance and Repair of the radio
    Tuning Band Modules for best performance.
    Remove main circuit board from chassis to access both sides of system board
    Install main circuit board back into chassis
    Minimum checks before power up after maintenance
    Replacement of DC feed protection diode
    Replacement of Q10 (transmitter final)
    Replacement of DDS encoder
    Replacement of display screen
    Replacement of Volume potentiometer


    Data for system components (replacement parts listing)

    Hints, Tips, Kinks

    Recommended items not supplied with radio set

    Building a portable DC power system

    This Guide is focused on the new amateur population providing simplified:
    • Diagrams of important systems and sub-systems.
    • Troubleshooting and maintenance steps that may be taken with minimal test equipment. I explain how to use the listed test equipment and how to build some of your own.
    • A limited parts listing for those items most likely to need replacement at some point in the life of the radio set. I'll explain how to replace those parts and hopefully allow you to get your rig up and running.
    • I also provide at least one source (available at the time of this writing) and common part numbers to source the parts for yourself in the future.

    I am offering this guide to the 9200 community at no charge.

    Send me your QSL card with a good email address and I will send you a PDF copy of the manual, over 50 pages, with multiple digital illustrations.

    PM me to get my address for where to send your QSL card.
    Last edited: Mar 21, 2016
    Ganado, hitchcock4 and Tobit like this.
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