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Old September 30th 03, 11:11 PM
Bill
 
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Default Issues with old Royal 1000

Hello All:
I have a royal 1000 Transoceanic that has some audio problems. The
sound required almost FULL volume and was very weak, and distorted. I
checked al the transistor bias voltages, and began to signal trace. I
was losing level across the volume POT, and decided to replace the
coupling caps (5uf caps coupling into and out of the volume POT). This
restored the volume; it can play LOUD now, but the audio still is not
what I would call 'quality'.

Here is what I have looked at so far:

1) Substituted the speaker; no improvement.

2) Placed a 10 ohm, 5W resistor across the speaker terminals as a
'load', injected a 1kHz sinewave into the audio driver. At FULL
Volume, I can measure with a scope 5Vp-p across the resistor load
(pretty good, 2.5W, right), and no clipping. The tone pot seems to
attenuate the sinewave like it should, but I do not see any clipping,
or distortion, or noise, etc.

3) I went ahead and replaced all the electrolytics in the B+ supply.

I have a Royal 3000 (similar radio) that sounds really good, but this
1000 sounds 'tinny' and slightly distorted.

Any help is appreciated!

Thanks,

Bill