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

Bill wrote:
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



Hello, Bill.

I've had similar issues with my R-3000's, of which I have, 5
(don't ask.) And similar symptoms with my Telefunken Opus Royale,
but that's just an amusement at this stage.

Look at the caps around the tone control. One of them is pretty
close to the chassis. As on my 3000, this one, through decades of
jostling around, and general age, the outer foil was coming into
contact with the metal of the chassis. With pretty dramatic
results. It sounds like this isn't exactly the case with your 1000,
but if there's loss to chassis at this particular cap, distortion
will result.

Not likely that there are problems with the B+ caps, given your
symptoms, but at this age, they were probably due to come out
anyway. So, you've saved yourself future grief.

Consider replacing all the electrolytics, as well as the tubulars
throughout the unit. Leaking or dried out electrolytics will account
for exactly the sound you currently enjoy. And lead to other
problems as well. Perforated tubulars, especially with the small
currents drawn by these circuits will not display a loss of volume,
so much as a loss of signal quality. Hit them each with a blast of
Freez-it, or an equivalent chilling spray. If the character of the
sound changes (as happened with the Opus and one of my 3000's)
you've got your defective part.

My advice is to replace all the caps--electrolytics, tubulars,
even ceramics---with good quality parts. Tubulars and ceramics can
be replaced with Sprague Orange Drops--Sprague has other types to
replace the smaller ceramics, but using mylar, or polystyrene
dielectrics which offer much better audio performance than ceramic
in a package about the same size.

Since it's tough to get in there and dig out all those pieces,
you 'll not want to do it more than once. So doing it all now will
save you a lot of headaches in the future.

Finally, take a look at the output transistors. They're not of
the heartiest variety. And it's possible for one to go south
without an outright failure. This would account for higher
distortion, but with plenty of audio, what's there anyway, and you'd
still get fairly normal readings for voltage and bias. (I"m
guessing you're using a high impedance voltmeter, like a DVM or a
VTVM...otherwise you might be loading the circuits you measure,
tainting your results. The output transistors are still available at
a real electronics supply store--read that NOT Radio Shack--or you
can get current substitutions through NTE, or ECG. They're less
than $4 a piece. And they're on sockets, no soldering required.
Just make sure you've got the right leads in the holes. A diagram is
on the inside back of your radio.

Start with the caps. I'm betting that will cure your problem.


Once you get it running the way you want it, you're going to
enjoy it a lot.


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