Kenwood TH-D72 external power

[krokus]

I purchased one of these at Dayton, and notices something odd in the owner's manual. The manual warns against running the radio off of 12VDC that is wired directly to an automotive system. Instead, the manual says to use an adapter with a DC-DC convertor, or the radio can be damaged.

Does anyone know what type(s) of damage? I have run my other Kenwood handhelds directly, so I wonder what has changed.

 

[kb2vxa]

Damage like letting the smoke out. The input voltage range is 7-9VDC so you need the PG-3J cigarette lighter adapter/cord to run it in the mobile.

Kenwood THD72A, Kenwood TH-D72A Amateur Radio Handi Talkie

 

[AK9R]

The TH-D72 instruction manual says on page 6:

Do not use the PG-2W to connect directly to a vehicle battery.

The PG-2W is a simple cable with a plug on one end that goes into the DC IN jack on the radio.

Then, on page 7, the manual talks about using the PG-2W to power the radio directly from a regulated DC power supply. It says that the supply voltage must be between 12.0 and 16.0 volts.

Based on this, my assumption is that Kenwood is concerned that a vehicle electrical system might exceed 16.0 volts and damage the radio.

 

[kb2vxa]

"Based on this, my assumption is that Kenwood is concerned that a vehicle electrical system might exceed 16.0 volts and damage the radio."

Probably correct, a 12V vehicle system can reach ~24V under fault conditions. I'll add my assumption to yours based on this:

Current Voltage Range
Battery terminal DC 5.5 V – 7.5V (standard voltage: DC 7.4V)
External battery terminal DC 12.0V – 16.0V (standard voltage: DC 13.8V)

Let's hope what they say about A-S-S-U-M-E doesn't apply to Kenwood, they used to make GREAT stereo equipment.

 

[krokus]

From what I'm reading here, there is not some weird thing about the radio's construction. (Like the case being tied to the +12V line.)

It was the mention of a DC-DC converter, and sounding like they wanted to isolation it provides, to prevent damage. (Not just power regulation.) None of that sat well with me, as it was contrary to my previous experience with their equipment.

 

[AK9R]

Well, there's not much intelligence to be gained from reading the label, but here goes:

Kenwood PG-3J Filtered Cigarette Lighter Cord
Output Max 2A
+ Pin Shell -
Kenwood Corporation
Japan

The housing has plenty of vents, but it's still difficult to see inside. I'm loathe to crack the thing apart. It wouldn't surprise me if there's a small switching DC-DC converter inside or maybe just a hefty filter circuit. The whole thing has more bulk than would be needed for just a linear voltage regulator.

 

[krokus]

I looked at the manual again, and I noticed where part of my confusion came from. The diagram used is marked for 24V automotive systems, and is rather unclear as to what is going on.

The same diagram and wording is in the manual for my TH-F6. (Which comes with the same wall charger, which is why I looked closer.)

 

[kb2vxa]

Hold on guys, I didn't say what else my research turned up. The PG-3J cigarette lighter cord is nothing more than a cigarette lighter plug and DC cord with a filter in the middle. No DC-DC converter here, none needed and if you don't get alternator whine with a straight through adapter cord you don't need the filter either.

Throw the manual in the drawer where it belongs and look at the adapter, notice the word "filtered".
The Kenwood PG-3J is a filtered cigarette lighter cord for the Kenwood TH-D72A.
Kenwood PG-3J Cigarette Lighter cord for TH-D72A

Don't let that 16V thing scare you, it's the design maximum for mobile solid state equipment in general and is not unique to Kenwood or any other.

 

[krokus]

Like a good geek, I was looking at the manual when I couldn't find a GPS mode/screen. I noticed the diagram as I was flipping by, and the DC-DC convertor in a 12V line, with warning of damage without it, caught my attention.

I just did not look close enough.

I do wonder how often there are 24V automotive systems, that are wired into the cab? Everything I have seen, in recent years, had 12V to the cab.

 

[kc0kp]

I purchased one of these at Dayton, and notices something odd in the owner's manual. The manual warns against running the radio off of 12VDC that is wired directly to an automotive system. Instead, the manual says to use an adapter with a DC-DC convertor, or the radio can be damaged.

Does anyone know what type(s) of damage? I have run my other Kenwood handhelds directly, so I wonder what has changed.

Resurrecting an old thread: SInce everyone avoided taking the adaptor apart, I did. Mine killed a fuse and then with a new fuse it did not work. Inside the shell are an MOV, a disc ceramic and an electrolytic on the input. That goes to a three terminal regulator mounted on a heat sink. Another terminal feeds the output to the radio with another smaller electrolytic and disc ceramic. The third terminal is referenced through a 20 ohm resister to ground.
Bottom line, it is NOT just a filter but a regulated power supply lowering the 12 Vdc. to I presume the 7 volts for powering the radio and running the radio on 12V would not be recommended, even if it is working for you.
My three terminal regulator is not passing any voltage. If there are numbers on it, they are unreadable so I bought a new one.
Craig