items relating to radio repairs
A really big thank you to Steve G0OYQ for having in stock a replacement MH-48A6J microphone cable for my Yaesu 7800. For some reason, the rubber on the original had started to fray.
Three self tapping screws to take the fist mic apart, and the replacement cable plugs in at both ends, and the radio is back on the air.
My Yaesu 7800 is used for mobile 70cm repeater operations.
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.