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Electrolytic Capacitor Beovox s45 6302

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freddy63
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freddy63 posted on Tue, Dec 15 2020 3:21 PM

Thought i might replace the original capacitors in my Beovox s45.

Bought six inexpensive Monacor 15uF NP 35VAC crossover caps. They are slightly smaller than the originals.

Surprisingly, the original capacitors all measured very good tolerance, even better than the new ones.

So i replaced just one speaker with the new capacitors and connected the speakers to the beomaster 2400 to see if i could hear any difference between the speakers, well i couldn't hear any difference whatsoever.

So what should i do now?

Put the old capacitors back in or go ahead and replace with the new ones.

Not a big issue, but i can't help thinking why replace old capacitors that seem better than new ones.

Any thoughts welcome.

 

 


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Dillen
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Dillen replied on Tue, Dec 15 2020 4:06 PM

So basically, you are comparing brand new (pretty much) cheapest caps with 40 year old (pretty much) highest quality caps and
found out, that the new modern cheap ones are only almost as good as the old high quality ones are after 40+ years?

Perhaps I am the only one feeling it's like your story has part of a chapter missing, but at least you found out, that replacing old
high quality components with new cheap stuff isn't worth it.

To that I agree.

Has your Beomaster 2400 been restored?
And was it done using cheap caps?

Martin

freddy63
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Hello, yes the missing chapter is, I replaced all the electrolytic capacitors, lamps and rectifier on the beomaster 2400 a week ago. I bought the capacitor kit from you a few years ago, but never got round to getting it done, until now. In your cap kit were nichicon, rubycon, panasonic, philips and jamicon. I don't know if they are cheap caps or not, but they are reputable makes, apart from maybe jamicon.

I like keeping the vintage as vintage as possible, not going to replace light bulbs with LEDs, i've seen that done a lot here, or try to upgrade anything unless it has any real benefit.

But i thought after recapping the 2400 I'd look into the speakers and replace the 40 year old capacitors. I read your posts about why it's not worth not using polypropylene in beovox, so i went for electrolytic and found out that the original capacitors were just fine(under the Peak meter) and also that the new monacor capacitors might not be as good as the old original ones. Not a problem, I didn't cut the cap leads, so i can put them back in if i want to.

Which capacitors would you suggest using?

BTW, I emailed you about a rabbits' ear antenna a few days ago.

Frederic

 


Dillen
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Dillen replied on Wed, Dec 16 2020 8:44 AM

You can trust the kit contents.
Some caps were deliberately chosen because of the positions they work in.
F.e. there are places where "very non-" low-ESR caps are needed and some of the "trending" brands simply can't supply suitable components for this.

Anyway, I'm not sure I would choose a Beomaster 2400 as the source when evaluating or selecting speaker capacitors.
It's a wonderful receiver in its own right, and definitely one of my own favorites, but it was never spec'ed very
high and, surely, the Beomaster will be the weakest link in the Beomaster 2400-Beovox S45 setup in any case.

As said, the original caps were of a very high quality. Roederstein capacitors were actually some of the better ones on
the market back then.
Where almost all of the well-known plastic-housed cylindrical ROE ones are bad or at least marginal by now, particularly the
red and orange ones (with the older grey ones curiously being slightly better - but still not good anymore),
the matt grey and golden bipolar ones that B&Os used heavily for their speakers, proved to last better.
Some are still surprisingly fine, which may be the case in your speakers, but most will definitely need attention after 30-40+ years, which should come as less of a surprise.

Generally, when checking the condition of a capacitor; Capacitance and ESR meters are all nice and fine, but check the leakage too. That's where f.e. the old wax-paper capacitors fall through and what makes them fail in circuit rather than lack of capacitance.

I agree on keeping the vintage. If you want modern sound and feel, buy something modern.

I also still would recommend electrolytics in speakers where circuits were designed for electrolytics.
Monacor is a joker. Sometimes you will get very good quality, other times.. well.. not so good quality. Even if not always cheap, but expensive doesn't always mean better.
You won't find Monacor caps in my drawer.

Many of the capacitors I use for restoration and repair jobs and also in the speaker capacitor kits I provide are produced specifically to get as close as possible to the specs of the original caps (when they were new).
Most owners hear a distinct and clear difference when replacing old with new. And even if the original caps are still
found good, they are going to fail sooner rather than later, and new capacitors would be the better solution.
Certainly if you already have the old ones out.
But if you feel your speakers are still playing fine with the original caps, you are of course free to leave them as-is.

The price of original B&O rabbit ears antennas are often higher than that of the receiver they will be connected to.
I have seen them sold for more than 300 euros, so the one you showed me could be a bargain.
Sorry, I don' t have any. 

Martin

freddy63
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Yes, i trust that the components i've purchased from you are the best suited. I have in the past bought two woofers from you, one for the beovox s45(6302) and another for 2600(6237) and they both work fine, thank you. I also have a pair of beovox s60(6303) with their trumpet stands and original capacitors.

I saw on your Beoparts-shop a capacitor kit for the beovox s45(6302), so I think I'll order them and see how it goes. Any coupons available before I order?

I don't have much choice when trying the speakers on a different source, just a JVC amplifier-tuner and a Aiwa A22 Micro Component Stereo Amplifier, both from the 1980s', probably no better than the beomaster 2400.

When checking capacitors, I have basic instruments as you can see from the photo, I can't check leakage with high voltage, I just don't have that kind of equipment.

One reason I got involved with electronics, is I guess like many others is the satisfaction of repairing things oneself. But I can only go so far, electronics is complicated stuff. All the beomaster needed was a cap replacement, I didn't change the no-load idle trimmers, just checked them, one was about 5mV the other 8mV, so I left them alone.

But another reason is that there are no longer any near by shops where you can go to to get your hi-fi equipment serviced anymore. Sending out equipment through the post office to a repair shop miles away is expensive and is risky!

Frederic


Dillen
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Dillen replied on Wed, Dec 16 2020 2:55 PM

"one was about 5mV the other 8mV, so I left them alone"
This is to low and will give crossover distortion.
I suggest you replace the trimmers and put the idle right.

Martin

freddy63
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Thanks for the advice.I could only get them in 220 ohms.

One in multiturn and the other in one turn.

Can I use them? The originals are rated at 250 ohms or I could try adjusting them rather than replacing them.

Frederic


Dillen
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Dillen replied on Wed, Dec 16 2020 4:07 PM

220 Ohms is fine.

Do one channel at a time.
Beomaster at room temperature (cooling fins).
No speakers attached.
Start with trimmer in center position. 
Switch on by selecting Tape (with no source connected to the tape input), take the volume down to zero and monitor the idle current from the time of power up.
Adjust to the setting mentioned in the service manual.
Keep an eye on it for the next five minutes or so, follow up with the adjustment if it creeps a bit (it will).
After a maximum of five minutes it should settle.
Do the other channel.
Done.

If the idle runs astray at any point, power off and diagnose.

Martin

freddy63
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I replaced the idle trimmers R249(R349) with Vishay 220 ohms multiturn.
Used four hook probes, two across R256 and R356. I did this from underneath the PCB on the solder joints and secured the probes with tape, flipped the beomaster back to it's normal position and started adjusting.
I coulddn't get a stable 12mV, it shifts between 11.5mV and 12.7mV.
When I use the peak setting on my multimeter, it will show me the minimum and maximum readings and that shows 7mV to 17mV.
I don't know if this is a problem and I wouldn't where to look if I had to solve this issue.

Frederic

Dillen
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Dillen replied on Thu, Dec 17 2020 10:21 AM

All fine!
The drifting is from components warming up.
Any drift in excess of a few milivolts is usually down to bad thermal coupling from the output stage transistors to the cooling fins (and the heat sensing component if present).

Martin

freddy63
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freddy63 replied on Thu, Dec 17 2020 11:12 AM

Well, that's good news,
I can now get back to my beovox capacitor replacement and then look into the beogram 4002 and see if it's working after years of storage.
Thank you for your time and help, it's good to have some advice from a professional, otherwise the B&O would have ended up in the attic.

Frederic

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