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Old 25-08-2007, 08:33   #1
David G4DMP
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Morphy Richards 27024

The audio from the internal speakers of the 27024 leaves much to be desired, the sound being very much lacking in top. Despite there being a crossover network using surface mount components on the main PCB, there appears to be almost no audio coming from the tweeter.

The quality can be improved by feeding the tweeter via a capacitor from the main speaker connection. I disconnected the tweeter from the PCB and connected the black wire to main speaker. I then connected the red wire from the tweeter via a 32F, 50v wkg non-polarised capacitor to the red connection of the main speaker.

I have also carried out this modification to the MR 27025 Internet Radio and both radios are now giving a more balanced output. You cannow actually hear sound coming from the tweeter!

73

David G4DMP
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Old 25-08-2007, 17:32   #2
mitajohn
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Well done ! I believe that the cap's value is big for the tweeter. If it is 5 - 10 uF and the tweeter is 8 Ohm then you have a 6 dB point at ~4 - 2 kHz good enough for the tweeter. The 32 uF results at a 6 dB point ~600 Hz quite low for the tweeter.
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Old 25-08-2007, 18:11   #3
David G4DMP
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Quote:
Originally Posted by mitajohn
Well done ! I believe that the cap's value is big for the tweeter. If it is 5 - 10 uF and the tweeter is 8 Ohm then you have a 6 dB point at ~4 - 2 kHz good enough for the tweeter. The 32 uF results at a 6 dB point ~600 Hz quite low for the tweeter.

Thank you, John. I have just changed the 32F to an 8F capacitor in the 27024 and in the 27025 radios and the audio quality is even better! I see that my local electronic store (Maplin) sell 10F 50V non-polarised electrolyics for only about 0.20 for anyone wishing to carry out the modification in the UK.

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David
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Old 26-08-2007, 14:59   #4
Digger
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Hi,

Never mind capacitors at all. Just connect the tweeter in parallel to the large speaker in the Morphy Richards. I stuffed some rock-wool loosely into the cabinet, this improved the sound even more.

I put a couple of response curves here:

http://www.drmrx.org/forum/showthread.php?t=1514&page=2

See #23, #25, #26 and #27. The posts are in German, the response curves are not
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Old 30-11-2008, 20:32   #5
Digger
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Lousy AC adapter

Today, for the first time I enjoyed Beethoven' s 9th from DW on the Morphy Richards in the livingroom with the built-in telescopic antenna running on 230 VAC with the AC power supply which came with the receiver!

If you take a hammer and chisel, break the cover of the AC supply apart, solder 4 pcs of 10 nF capacitors across the rectifier diodes, then it works! All the horrible buzz and noise from the power adapter disappears!

Later in the evening I heard AIR Khampur, Langenberg and RAI on 846 kHz without problems. Why can't they think of this at the manufacturers???? A lousy AC adapter ruins the reception totally...
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Old 01-12-2008, 06:20   #6
mvs sarma
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Quote:
Originally Posted by Digger
Today, for the first time I enjoyed Beethoven' s 9th from DW on the Morphy Richards in the livingroom with the built-in telescopic antenna running on 230 VAC with the AC power supply which came with the receiver!

If you take a hammer and chisel, break the cover of the AC supply apart, solder 4 pcs of 10 nF capacitors across the rectifier diodes, then it works! All the horrible buzz and noise from the power adapter disappears!

Later in the evening I heard AIR Khampur, Langenberg and RAI on 846 kHz without problems. Why can't they think of this at the manufacturers???? A lousy AC adapter ruins the reception totally...
You have rightly pointed. In fact we used capacitors across each diode,instead of searching where to keep, as it depended on characteristics of diodes.
These LOUSY ones and their manufacturers aim at cheapness, and nothing more.The Transformers become too hot as they would use low quantity and/or quality of core.

May I add another point that most adopters or wall warts what ever they are called, can well have regulators inside (linear though, as switching supplies are detrimental for radio Rx use.) and give a good stabilization and as on date adding a regulator for say 250 or 500mA load is not costly and it would help for good health of most equipment.

They can better stop making orthodox unregulated junk.
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Old 05-12-2016, 17:02   #7
ianf
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Just thought I would let the Forum know I will be selling the last batch of 27024 radios on Amazon in the new year,
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Old 06-12-2016, 18:48   #8
PhilipOneL
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Ian, is there any difference between this batch and the earlier ones?
(Later serial numbers, previously owned, etc.?)


Philip
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Old 13-01-2017, 08:00   #9
ianf
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Phillip
These are the last batch I've managed to obtain, they are 27024EE, the cartons indicate they are the late production run, one of the receivers I've looked at it serial number 60004537, I will upgrade firmware if required before shipping
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Old 14-01-2017, 00:25   #10
PhilipOneL
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As peculiar as their operation is, I like my 27024s (I have two) and use them every day. I have replaced the main tuning button and some condensors on one of them but, other than that, they've held up well.
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