Ancestors

Written by Dr David Mills on 2025-01-24 at 19:53

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.

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Written by Dr David Mills on 2025-01-25 at 09:43

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.

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Written by Dr David Mills on 2025-01-26 at 18:51

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.

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Written by Dr David Mills on 2025-01-26 at 20:06

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.

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Toot

Written by Dr David Mills on 2025-01-27 at 20:45

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.

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Descendants

Written by Dr David Mills on 2025-01-27 at 21:13

This is what the service manual gives:

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Written by Dr David Mills on 2025-01-30 at 09:10

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.

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Written by NormanDunbar on 2025-01-27 at 20:48

@Dtl Good luck!

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Written by WokStation on 2025-01-27 at 20:48

@Dtl are they hidden underneath?

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Written by Dr David Mills on 2025-01-27 at 20:51

@wokstation I've looked, but I can't see them. If you try to lever up the board you can feel it is held down, but I can't see what by.

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Written by WokStation on 2025-01-27 at 21:04

@Dtl got an endoscope? Or a raspberry pi camera?

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Written by Dr David Mills on 2025-01-27 at 21:13

@wokstation somewhere

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Written by g7kse on 2025-01-27 at 22:21

@Dtl perfectly clear to me. Is a road runner and a coyote on other pages?

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Written by Philip Bragg on 2025-01-30 at 09:37

@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!

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Written by Dr David Mills on 2025-01-30 at 09:49

@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.

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Written by Niels Moseley on 2025-01-27 at 21:14

@Dtl perhaps they mean spaces? #TabsVsSpaces

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Written by Dr David Mills on 2025-01-27 at 21:21

@trcwm Hehe

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