Dr David MillsJan 24, 2025
Having a first look at @doc's radio.
It's totally dead. Drawing a shade under 0.05mA I assume that is keeping some clock running or something, but nothing else causes any more current to be drawn.
This should be an interesting repair.
Show threadDr David MillsJan 25, 2025
I did a little bit more investigation on this radio last night, there's an internal DC-DC converter that turns 4.5V into 9V. That isn't working. I need to check if that's waiting for some enable signal.
Putting a switching converter in a radio is an interesting idea. I wonder how they filter the noise.
Show threadDr David MillsJan 26, 2025
Back at this radio. There's no significant voltage across the input to the DCDC converter. All there is before that is a pair of transistors a switch and a couple of switched jack sockets.
I've got the steady arm out for the camera as I've had a comment or two that my repair videos are a bit shaky. Fair enough.
Show threadDr David MillsJan 26, 2025

I'm getting more convinced that this radio has an electromechanical issue, if I put pressure on the board I can increase the current consumption from 0.1mA to 1mA.
There are a couple of switched jack sockets that are in the area of the board I'm investigating. I'll give them a deoxit soak and see if that clears things up.

Still 2/3rds of sod all on the capacitors, so something is high resistance either way.

Show threadDr David MillsJan 27, 2025
Trying to get the PCB out of the radio. The service manual suggests it should just hinge up if you release two tabs, but I can't find the tabs.
Show threadDr David MillsJan 27, 2025
This is what the service manual gives:
Show threadDr David MillsJan 30, 2025
Last night I got the radio to briefly draw some current. A faint hiss from the speaker when at max volume and I think I just caught a whistle as it tuned though a carrier, but then nothing.
It was back to zero current this morning.
Show threadPhilip Bragg
@Dtl I had the newer version of this radio for a while. It was a cantankerous thing, there was an inadvisable arrangement for getting battery power to the PCB involving a sharp bit of metal touching a tinned track. Mine also had an intermittent fault in the synchronous detector (a 4066) which i don't think the older radio had. I really liked the radio when it worked but it was a horrible thing to work on and I eventually sold it as non-working for a token amount at a rally so someone else could experience its personality!
Jan 30, 2025 at 9:37amWeb
Show threadDr David MillsJan 30, 2025
@synx508 Yep - there's the same bit of metal poking a track for power arrangement on this.
It's also pretty power hungry - it was drawing 250mA
I'll be very happy if I can receive a signal on it.