Thank you for tuning in! Always glad to know there’s somebody out there interested in what I’m doing!

Update:

Alright, I realized something. I might have misunderstood something. The analog radio circuitry is supposed to be turned off thru the power MOSFET 2SJ615, marked Q1008 in the circuit. This is contrary to my previous understanding that the circuitry in question remains on regardless the state. The MOSFET is driven directly by a pin in the microcontroller. The signal line is called “REG SW” in the circuit diagram, which I am guessing signifies “Regulator Switch”.

Therefore, in my renewed understanding, the 13.8V power should only goes to three different paths:

• the power MOSFET, that gatekeeps it from the rest of the analog circuitry on the main board
• the logic board, where the microcontroller lies, with its own set of power regulation
• the final RF amplifier (irrelevant for this matter)

You can definutely put a torque limiter on your hands.

Slot heads never wear out.

Update:

I have narrowed down the root cause to the shift register. However, it was not the way that I thought of before.

After further research I’ve learned that the shift register in question was supposed to remain in its last state when the rig enters the standby mode. It’s supposed to stay that way, even without the data or the clock signal, as there should be no strobe signal going in. This is the normal behavior for shift registers.

What seems to happen during the anomalous state is that a stray voltage spike goes into the strobe signal pin, opening it up for the data input, which it take as all zero, since there’s no data going in. This is why all its output pins have 0v instead of the expecter 5v.

I made the above discovery basically by replacing the shift register with a new one. The original CD4094B is hard to come by, and I don’t trust the Chinese clone, so I opted for a more modern replacement, the CD74HC4094. According to their datasheets, they both should be virtually interchangable. Turned out it indeed was the same, down to that damned loud static noise!

At some point, I accidentally shorted the strobe pin with the Vcc and the loud static noise appeared. I then removed the shift register and tested for connection between the two pins thru their empty solder pads. To my surprise, it only made connections with the logic unit connected, with resistance within megaohm magnitude. They make no connection at all when the logic unit is detached.

Good question, and the answer is yes. I have tested for continuity, the clock line thruout the board is indeed connected to the pin in question on the microcontroller.

Not sure if it’s really a bug. I think it’s probably more like a hack. Many people have been using this thing since 2009, and the only complaints I found was about how heavy this thing is or how much heat it generates, both of which seems to be by design.

My case should be somewhat unique, due to the history of unsupervised mod done to it.

In case anyone is wondering if I have to endure such loud noise, I don’t.

To help with my sanity (as well as my family’s), I decided to quickly put together an external loudspeaker out of some spare components from my drawer.

• an LM386 audio amplifier
• a speaker with 8-ohm and 1 watt, similar to the rig’s
• LM7812 linear regulator with 12 volt output, just in case, since I’m using the same power supply as my rig
• supporting passives
• 10k ohm potentiometer to control the volume — this is important, since the static noise always comes at the rig’s maximum volume

To ensure that I’d able to catch the issue without being driven crazy, I tuned the external speaker to the minimum volume where I could hear it by turning the rig’s volume all the way up and turning off the squelch with the radio on, simulating the loud static.

I then turned the radio off, still connected to the running DC power and the external speaker. Within a couple minutes, the whole contraption performed exactly like I hoped for, and thus, I was able to sanely conduct my investigation.

Thanks for the explaination!

The other day I was checking out the datasheet for my Yaesu monobander’s final amp, and I noticed that it is able to performs optimally up to its advertised 80w only between 144mhz and 148mhz, while outside of that it’s capped to 60w. I’m pretty sure this is related to what you just explained.

Overall, I feel like the 2m band is like a kiddie playground, while the grownups are hanging out with their big antennas on HF.

What do you mean? Can you elaborate?

Perhaps it’s a regional thing. It is quite the wilde west where I’m from after all.

For the Yaesu FT-2900R, I indeed acquired this second hand, but I also got myself a new old stock FT-60R that seems to be able to transmit outside the HAM band for both 2m and 70cm out-of-box.

I have a few monobanders by Yaesu & Icom, and all of them are able to ony only Rx but also Tx outside of the HAM freqs. Of course, I’d be very careful with them 😇

Update: I accidentally shorted some component’s pins and the it failed to deliver the specified power once again. Guess now I know what happened to the old component I replaced. Luckily I have a spare.

Update: I decided to get myself a linear power supply. The issue persists. Therefore, it’s not power supply issue. The good news is, I now have no issue transmitting at full 75w power.

That is exactly right.

Update: The correct part has arrived. After replacing it, no more voltage drop!

Update: After inspecting the components’ voltages across the circuit and cross-checking it with the service manual, I found one of the transistors, marked Q1008 in the diagram, might be out of spec. The component should’ve been 2SJ615. Who knows what the phony seller did to it, but it was outputing well below the specified 13.5-13.8V (yes, I made sure the input was correct).

The power supply is rated for 360 watt, but who knows, it is a cheap chinese product after all.

The link doesn’t seem to work.

Is that the Duomo?

I’m learning Italian, just passed A2, and am probably gonna continue with B1 if the course schedule is right.

At the moment, I am having a vacation in Italy, and I realized that there’s no more effective way than having use cases that you can relate on a personal level.