Radio Repairs

ICOM 725 HF Rig
ICOM 725 HF Rig avatar

Some advice please…

I have a mint ICOM 725 all mode HF rig with all the bells and whistles (well for a classic rig), and it has all the ICOM options you can add to them, but, it has started with a curious fault that has me puzzled.

All the back lights on the front panel are not working, but, 10 years ago, these were changed to 12v LEDs due to blown blubs at the same time the rig was opened up for 5MHz transmit.

The rig works fine, and has for the last 12 years of ownership, but, only recently with no LED back lights to the front panel.

Today, I took it apart, to trace the fault, and I appear to have a short circuit across the LEDs, no other work has been carried out on the rig for 10 years.

According to the service manual, I should see a voltage of 11.5v to the back lights that are regulated down from 13.1v with two transistors and voltage divider resistors, see the relevant section of the diagram.

I am seeing 0v on this line and there is a very light smell of plastic burning, but, I can’t tell from which component. This line is showing a short to chassis.

My question is, do (or can) transistors just burn out and go short circuit to ground, well all current flowing to ground? What is the best way to test these in circuit, or, do I need to de-solder?  I look forward to hearing from someone so that I can get this classic rig back on the air again. Being so lightweight, I love it for both shack and portable use and is my favourite old HF rig.

Website

Website Future 2024
Website Future 2024 avatar

I originally got the domain name M0INI.radio so that I could have a radio related domain for email.

Since 2017 when the domain was granted by the .radio authority, (you have to prove you have a link to radio or a radio license from a licensing authority), I setup a basic place holder website, and started using the domain for email only.

However, I have now decided, that I will expand the domains usage to also be used for blogging for the station and what I am up to as a radio amateur.

Therefore, during 2024 and onwards, there will be regular posts on the stations website.

West Manchester Radio Club

Becoming the Secretary of the West Manchester Radio Club
Becoming the Secretary of the West Manchester Radio Club avatar

After clubs started opening up after COVID, I was asked by the committee of the West Manchester Radio Club if I would be so kind to support the club and become the club secretary.

My main concern was that I live 65 miles away..!  And, I won’t be at club every week.  However, since I mix business with pleasure, I am still able to get to club one or two times a month.

So with this concern mentioned, the committee was still happy with this, and so I accepted the position with pleasure as “Acting Secretary” until the next AGM in January 2022.  This will allow the club some stability and help to “get the club going” post COVID.

I must say, I find it a great honour to be asked, and I will do the job to the best of my abilities.

The West Manchester Radio Club’s website is at… http://www.wmrc.co.uk/

Bolton Wireless Club, General, Memories

New Website
New Website avatar

Mark M0INI
Mark Andrew Smith M0INI

Hello and welcome to my new website for my amateur radio station M0INI.  This is the story of how and why I got into amateur radio.

My father was a radio operator with the Royal Corps of Signals, and had a background in electro-mechanical engineering all his life.  Obviously, with my fathers influence, as a young child, I had an interest in radio.

Edward “Eddie” Smith

After leaving the army, my father was invited to teach with the Marconi School, but decided to go into engineering instead.  He was never licensed.

I have shown a keen interest in radio since before CB was legalised in the UK, however, as a teen, I had a choice, CB or computers, and I chose computers.  This was my first computer, an Acorn Electron, seen here still working today and operated by my son.

Acorn Electron

Like my father, we both didn’t go into a radio background, so it wasn’t until 2005 that I started to show an interest in radio again, and got on the air using CB, resurrecting my old handle from the 80’s of “Spark Transmitter”, a reference to the early days of radio and Marconi.

However, I wanted more, and looked for a radio club to study for my foundation license.

With the help of the West Manchester Radio Club, I quickly became licensed as M6INI, then later as M0INI with the help of Bolton Wireless Club.