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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 7th Feb 2019, 3:10 pm   #1
Julesomega
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Default Panasonic RF-D1

The RF-D1 was an early portable radio for the new DAB system in 2004. I was given mine by a friend who had not managed to scan for any stations, and I found it had good sensitivity and pleasing audio, I only wish it had a DAB-derived clock. Two common faults may be encountered with the RF-D1, and the more serious will have caused the failure of any units which have seen regular use.

First is failure of the voltage regulator, which uses a power device with no heatsink. The mains adaptor gives an input voltage of up to 11.5V, leading to dissipation of 2 or 3W in this device, which may die from the heat generated, or more commonly can melt the solder on its leads and drop off the board. Replacement is quite straightforward but requires some ingenuity to provide meaningful heatsinking.The other reported fault is that the processor freezes and the display shows "F76 PDET". The reported solution to the problem is to press the Power and Menu buttons simultaneously for a few seconds, a couple of times if required. I have not encountered this problem. Panasonic have a good reputation for build quality so it is always worth trying to repair this model.

The supply regulator uses a PNP TO220 transistor type A2057 as the series pass element Q315 configured for low dropout, and any PNP TO220 type can be substituted. I long ago fitted a small heatsink.

Mine failed last week so I opened it up for a look and could see a scarred blob on a sub-board and a bulging 470 electrolytic which is across the supply rail. The blob had been a reverse-pol protection diode which had died valiantly, either because I had reverse-pol'd it when trying to run it on the bench PSU, or because of the electrolytic. Another SOT23 diode was fitted, anode to Gnd but a resistance check showed a dead short across it. It was still shorted when the diode was removed, and it turns out that the diode is switched into use only when the external power jack is inserted. This changes some internal switching which is hidden from view. The 470 was replaced and the board fuse which had failed, power applied, and when the 'on' button was pressed it sprang to life.

The only remaining job was to reassemble the boards into the radio, which was fraught with aggrevations so I offer my advice based on hard experience. To dismantle you need a #1 Philips for the body and PCB screws and a #0 for the three screws which hold the tuner PCB. Remove also the handle support piece which lies above the Ae skt, and remove the F-skt to withdraw the RF input board. Before replacing the main PCB ensure that the wire from the telecopic antenna is not trapped under the RF board, and the two wires from the battery compartment are not trapped under the main PCB. The front panel has a divider board which projects onto the main PCB: a line is marked on the PCB to show where it lies so ensure that no electrolytics are lying across the line and make sure Q305 and heatsink are clear.

The date codes on the speakers are 240604 in mine, btw. References to the faults can be found on forums from 2005 such as
radioandtelly.co.uk
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Old 7th Feb 2019, 10:43 pm   #2
Wellington
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Thumbs up Re: Panasonic RF-D1

Nice write up, Julian!

I daresay many people would've consigned that to the tip, but it's good to be reminded that even modern stuff can be brought back to life. Makes me feel better about never throwing anything away!
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Old 6th May 2019, 3:07 pm   #3
ColinB
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Default Re: Panasonic RF-D1

Just dragging this thread up, as my parents neighbours have presented me with one of these to repair.

My first check was the fuse, which was open.

Looking around the boards didn't show any bulging caps or other glaring problems, so I have (temporarily) by-passed it, and the unit works.

I am running the unit from a regulated 9V adapter as the original adapter is giving out 13.47V off-load, I'm assuming that this was the cause of the fuse blowing, and I can replace it?

The unit has been tested on FM and DAB, and seems quite happy.

Questions are, what value fuse should I fit? and do we think that the higher voltage saw off the original fuse?

Thanks,

Colin
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Old 6th May 2019, 7:44 pm   #4
julie_m
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Default Re: Panasonic RF-D1

13.47V off-load wouldn't be unusual for an unregulated 9V supply using an old-fashioned transformer, especially if it was going to be expected to produce an amp or so. Measure the voltage under load and see how the voltage sags. If in doubt, replace the PSU with a regulated one of the same voltage and polarity and good for at least as much current as the original.

As far as selecting a replacement fuse goes, just measure the current drawn by the set with the volume turned up loud, and fit the next rating down. Ordinary glass fuses aren't even going to think about blowing till they see about twice the rated current.

It's unlikely for a faulty PSU to blow a fuse, because a set with a voltage regulator won't draw any extra current at higher voltage. But it's also possible that there is some sort of last-line-of-defence protection circuit which shorts out the supply and blows the fuse in the event of an overvoltage. You could test for the presence of such a circuit using a current-limited bench power supply, if you felt so inclined, but do not leave it in the protection-active state for any length of time: in real life, it only has to last long enough for the fuse to blow!
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Old 8th May 2019, 6:45 am   #5
ColinB
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Default Re: Panasonic RF-D1

Hi julie_m,

Thanks, great post, I agree with what you wrote, I was just surprised at how high the unregulated PSU output was. I'd have assumed maybe 10-11 volts or so...

Anyway, I'll return the set with the regulated unit, which seems to work well.

Cheers,

Colin
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Old 8th May 2019, 7:52 am   #6
Nickthedentist
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Default Re: Panasonic RF-D1

Thanks for an interesting write-up from me too.

I have one, fished out of the WEE bin at Sainsbury's a few years ago. This was suffering from a broken on/off switch, the plastic bits linking the button to the tact switch having fractured. I repaired it with a small salvaged panel-mount momentary switch Araldited into the hole where the button originally sat, linked to the PCB with short insulated wires.

My parents use it every day and it's never let them down. I power it from an ex-camcorder PSU (the original couldn't be retrieved!) but my parents insist on switching it off at the wall, which probably accounts for the regulator not giving up the ghost.

N.
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Old 11th May 2019, 12:49 am   #7
Julesomega
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Default Re: Panasonic RF-D1

Good to hear of another RF-D1 retrieved. If you want it to have a long life, do pay heed to the power dissipation of the regulator transistor. If you are going to use an unregulated power unit of nominally 12V you will need some additional heat sinking to stop it melting off the board. My added heatsink is not shown in my photos but I suppose it was about 2 5cm of 2mm thick ali, bent to fit around the transistor.
Alternatively, use a regulated supply set to about 7.5V which is about the lowest voltage that the set will operate on, or choose an unregulated supply that drops to that level when the set is switched on. There will be negligible power dissipated when it is off so you do not need to worry about leaving the supply on when the set is off.
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