Yaesu MH-31 Microphone Failure

•February 17, 2019 • Leave a Comment

Problem: No transmit audio on the FT-857D tranceiver.  FM/AM/CW produced a carrier.

mh31a.PNG       mh31cart.PNG

RFO: Dynamic microphone cartridge failure.

Detecting failure.  Besides no transmit audio, measurement of the resistance between the two cartridge leads enabled diagnosis.  The cartridge should have with a normal resistance of between 200 to 600 ohms.  Instead the faulty cartridge presented an open (infinite) resistance as measured by a DVM



This was a bad dynamic mic cartridge that checked out with infinite R instead of 200 – 600 R. Given the mic was dead, seemed like a no-brainer to do the electret mic conversion since I had the parts.  Used the electret mic cartidge that came with the uBITX and followed m0ukd’s schematic. The utube is excellent with a very similar solution. QSO on 40m confirmed decent sound on the FT-857D with the new refurbished microphone.

Performed this mod with parts on hand , an electret mic cartridge from the uBITX project and a couple of caps on hand (47nf and 1 nf).

It’s important that there be capacitors in the signal path to block the +5v dc voltage.  I took some pains to insure there were no shorts since 5v would be bad news for a mic pre-amp or other circuitry downstream that is not expecting it.


The microphone now works and reportedly sounds good.



TS-590SG Power Cord – Reduced power, Reboots

•February 17, 2019 • Leave a Comment

20190216  Incident – TS590SG rebooted once while transmitting.   Later under testing into a dummy load, power was limited around 50 watts in CW mode, sometimes more, sometimes less.  The reboot occurred once or twice.  The lack of power affected all bands.

Reason for failure – the 25amp fuse holders and other connectors on the power cable for the TS590 oxidize over time and can cause significant power loss over time.  When the total current carrying capacity of the power cord assembly is reduced due to oxidation and gradual loss of the necessary gas tight metal to metal contact, the rig circuitry responds to the voltage drop by reducing power and related events may cause the system to reboot.

Recovery Actions Needed –  remove power cable, inspect, wipe all connectors clean, pull out, clean fuse contacts, or simply reseat the fuses.  Inspect Johnson power pole connectors and insure all connectors are seated fully.  When I inspected the fuse blades, they looked shiny and clean, but they may well have been the culprit.  The power pole connectors too are subject to oxidation and losses.

Result of maintenance actions:  Restoration of normal operation.

Other – the power limiting and reboot behavior made me wonder if  a serious electronic failure, e.g. of the final mosfet transistor amplifier, occurred.  Other accounts on the web may likewise be misleading, if only because fragments of information can be  misleading.

The  problems caused by power loss in the power supply cable are not widely known but amply documented; it’s possible to eventually find the needed information if your google-foo is strong. There is pertinent discussion online,  e.g. https://groups.io/g/TS-590/s  or on QRZ.   Before too long I was in contact with two hams in particular with direct experience with the problem. CE3DNP and W2JDB helped me zero in on the problem. Thanks guys – saved me a lot of time and effort!



Low noise event – 2Jan2018 …

•January 3, 2019 • Leave a Comment

1/2/2018 – on or about 2 jan 2019, I noticed that  the 40 meter noise floor  dropped from S9+5 to S3 (no preamp).

Noise canceling is no longer necessary.

The source of the noise is a mystery but seemed to be related to power, maybe a noisy always on device.  Hoping for the best.


FLDIGI CW Split Operation

•October 25, 2018 • Leave a Comment

oct 2018
Use FLDIGI for CW and how to use SPLIT in contests and for DX stations.




I can’t hear call signs at 30 wpm.  I could hear my call sign at 30wpm,  I could do limited contest and dxPedition cw without fldigi.  Until that day …



Computers in the shack 2018

•August 14, 2018 • Leave a Comment

2018-Computers: I use an Intel I3-4150 Dell mini-tower for its disk space and as my Win10 outpost until microsoft licenses me out into the cold.   CPU: i3-4150 @ 3.50 GHz / 8 GB

We’ll probably go one more round of hardware upgrades before we ditch Microsoft completely.  Ham radio apps, SDRs in particular, have not migrated fully to openSource, i.e. Linux, at least for the hardware I have.  And Windows is convenient for now (2018).  I use hand-me-down macbooks from my daughter and my sister for portable and some digital ops and for wireless ssh/x11 for the raspberry pi’s, and hard wire USB for arduino projects.  Often I’ll use a rapspberri pi to front end an arduino, and do arduino development from the pi, from a ssh to the pi from windows or osx.  I use raspberry pi’s for programming and development – mainly python, C, and perl languages.  The pi’s are more or less a dream come true for an old unix dog like myself.  As the need arises I use arduino’s, mainly the nano’s for projects needing microprocessors – they are to me suprisingly powerful C/C++ language developments platforms too which seems outlandish, but they can do some  significant number crunching on a thumbnail size chip.

MFJ-4125P Fan Noise

•April 7, 2018 • Leave a Comment

The MFJ-4125 switching power supply  has some notoriety for fan noise. MFJ uses a 60x60x15 mm fan from Yate Loon.  The high noise level is a result of running the fan at full blast.  Any noise abatement comes from dialing back the voltage going to the fan at the cost of reduced airflow, which brings us to the black art of form vrs function.  The problem is to reduce fan noise without adversely affecting the power supply circuitry of the power supply.

How much cooling is enough? Chose a fan, watched the failure rate of the power supply and if acceptable from a business standpoint, good enough.

The fan noise level is described by MFJ as “whisper quiet”.  On the sound scale, “whisper quiet” is 30dB.   My cell phone sound level app does seem to confirm a +- 30 dB level of noise coming from the supply fan, an example of  the double edged sword nature of truth in advertising.

Noise increases with airflow. I plotted the data (see the Yate Loon product data sheet (2) for it’s fan product line further down ).  I plotted out their four data points below which shows the interesting relationship between Airflow and Noise.


To reduce noise, reduce airflow by reducing RPM.  The human ear detects sound intensity in increments of a decibel or two.  For every increase in one  cubic foot a minute  airflow, there is a one to two dB increase in noise.  It should also be kept in mind that the human ear is a very poor temperature sensor without a lot of help.

Reduce RPM by reducing voltage – 4 diodes in series

A number of hams reported using 60Ω to 100Ω power resistors to drop the voltage and reduce fan rpm.  I am trying diodes instead of resistors since I don’t have the needed power resistors.  4 diodes in series produce a 25% voltage drop from 12V to 9V.  Noise decreased noticeably; every diode drops .7 v drop and each results in a small drop in noise, so this might have been 4 to 8 dB.  At 9v, the fan still makes noise. The question is what’s the impact on airflow and necessary cooling.  E.g  a 25% drop in airflow from  22 CFM  would be 16 CFM …  is that enough to make a difference in the power supply temperature?   {9/1/18 after a few months, still seems to be fine with no apparent ill effects.  Using a noise app on my phone, the fan now elevates background noise in the shack from  30 dB to 35 dB with the mic a few feet away from my operating position.}

There are many comments out there of hams who have installed resistors. Nobody has reported any issues with dropping the fan speed using resistors.  We’ll just sort of see how it goes with diodes.

I put a thermistor on the heat sink to enable monitoring the temp on it and set up my arduino thermistor .  (let’s put a thermistor in there – now that we have a small inventory in stock !)  From April to September, the power supply ran with diodes in the fan circuit with no ill effects.

9/1/19.  Did some power supply temperature test with TS590sg  transmitting into a dummy load.  PS heatsink temp rose from 84º F to 103º F  100 watt cw.  That’s not too bad I think.  (the ts-590sg rig remains cold to touch).   Under digital condition the temperature of the heat sink however goes to 123º F.  For this we’d want to be able to switch on full power to the fan.

Temperature controlled fan driver (4)
(Taming the MFJ-4125 PSU Fan)
Below is a schematic from G0KLA who used this circuit for regulating span feed from temperature for his linear amp power supply.   He used the same circuit with an MFJ-4125 and posted it ( see 4 ).   It’s the same analog control concept as ( #6).

4/8/18  I built out the circuit for testing.


C17  – electrolytic,  filter/time constant ?   R31 – the gate resistor 10k seems to be typical to protect the gate from transient voltage at the expense of switching speed.  Switching speed for turning on a fan is hardly critical. (5)

Test Session #1 – Standby noise of about 35 dB and 109º up to 50 dB+  and temps above 118º on 9/13.



9/13/18 Testing temperature driven fan controller-  finally.   Removed the  diode breakout and inserted the test unit.    Insertion notes:  for testing I tapped tge 12V on the rear panel, and attached fan leads directly to fan + and  minus – .   There is a better way.  Make a power cable to get the 12V from the fan power socket on the board, and provide two header pins for the fans power plug. This allows the fan circuit insertion without cutting / soldering  on the MFJ4125.

9/10/18 Results.   The circuit works well.  Maximum temperatures are about 118º F with full power digital operation.   I set the trigger point to occur at something close to 105º F by trial and error .  At this setting with transceivers powered up, the fan idles with heat sink temps around 105º and 110º and fan noise is barely audible with total ambient noise of about 35 dB.    On transmit, the fan speed revs up, and with a lot of transmitting activity like with a digital mode, the fan goes to full speed as the MOSFET switches on to deliver the full input voltage to the fan. The fan at full power adds another 10 to 15 dB of background noise.


The spec we’re most interested in is the junction temp of the power transistors attached to the heat sink .   Then the heat sink temperature might tell us if the cooling is enough.  We’re leaving this to another time.

9/10/18 Production Insertion Notes.   Came up with the better idea for how to make the insertion. Soldered two header pins to plug the fan end connector in.   Used a two pin socket to plug into the fan power supply socket on the rear of the 4125 main board.

(1) http://w9xc.net/w9xc-html-site/projects/mfj4125mods/mfj4125p-mods.html
(2) http://www.yateloon.com/en/product-38825/DC-FAN-SERIES-60x60x15.html
3) http://www.nmbtc.com/fans/white-papers/dc-brushless-cooling-behavior/
4) http://www.g0kla.com/workbench/2016-05-06.php  – heat sensitive ran speed reduction circuit.
(5) http://www.electronic-products-design.com/geek-area/electronics/mosfets/using-mosfets-as-general-switches
(6) https://www.google.com/search?q=using+mosfet+to+control+dc+motor&safe=off&tbm=isch&source=iu&ictx=1&fir=8VQ36z01EUPryM%253A%252CKpP3Zyk_V6miYM%252C_&usg=__qMZ6oTM2b7Ruq27wP5WeLTlBarU%3D&sa=X&ved=0ahUKEwiKrZ6a6a3aAhUQTawKHbWGAU4Q9QEIUzAE#imgrc=8VQ36z01EUPryM:

Fan Specifications 

The fan used OEM is a 60x60x15 mm 2 wire YateLoon S60SM-12 run at 12V with the fan load, 13.8v no load.   It’s

The specs and replacement information are included here because the originals bearings are on borrowed time and multiple re-lube operations.

Below: product sheet from Yate Loon (2).  YL has data on four different models of 60x60x25 fans with different motors.  Airfow and noise increase with RPM

fan specs

OEM Source (3) 60x60x20   

D60SM-12 Technical data:
Dimensions: 60x60x20mm
Nominal voltage: 12V
Nominal speed: 2700rpm
Airflow: 18CFM
Noise level: 30 dB(A)
Power consumption: 1,2W
With 3Pin Molex plug, 60cm cable and rpm signal

Instead of a genuine YL, here’s what I bought below.  It’s now plugged into the power supply and seems to be running fine.


12/13/2018  So far so good.  With only receivers on, the power supply fan is off.  At some point the fan my idle as the load increases.  On transmit, the heat rises in the PS, the fan rpm rises rapidly and continues until the heat drops.  If we stop transmitting the fan idles and eventually turns off.





Shipping Lithium batteries

•December 15, 2017 • Leave a Comment

After buying lithium cells for years from Battery Junction, Tenergy, and others, in Dec 2017,  Battery Junction will not ship batteries to Hawaii because their carriers all use air freight.

Today I ordered 4 CF123A rechargeable cells from Green Batteries.  Green batteries worked with me to find a solution.  The USPS allows air shipment of two batteries per package.  Green Batteries sent four CR123A rechargeable lithium ion batteries in two small packages which arrived in a few days.

So the future of the lithium battery segment of the industry is to find surface shipment qualified for hazmat shipping.  Nimh may be a different story still.  The air travel restrictions apply only to lithium, but demonstrably safe packing measures – factory packing if possible, taped terminals, individual plastic bags or containers are the minimum requirement.  Boxed and sealed to avoid contact with any object prevents short circuits. Most important, they must be carried on and cannot be checked.

June 28, 2016   https://support.myunu.com/hc/en-us/articles/221753607-Transportation-Security-Administration-TSA-Requirements-on-airplane-for-batteries

Lithium Ion Batteries: (a.k.a.: rechargeable lithium, lithium polymer, LIPO, secondary lithium). Passengers may carry all consumer-sized lithium ion batteries (up to 100 watt hours per battery). This size covers AA, AAA, cell phone, PDA, camera, camcorder, handheld game, tablet, portable drill, and standard laptop computer batteries. External chargers are also considered to be a battery. With airline approval, devices can contain larger lithium ion batteries (101-160 watt hours per battery), but spares of this size are limited to two batteries in carry-on baggage only.  … 

This criteria allows qualifies a 10 AH x 12V = 120 watt hours LiFePo4 battery for travel.  Two of these in parallel is 20 AH – the maximum allowed.


Carrying a small shipment of several lithium metal cells could be problematic.  This is where securing an online source is just better.