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A beomaster 6000

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Craig
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Craig posted on Wed, Jun 12 2019 7:05 PM

Following on from Peters BM8000 I have decided to take a look at this unit, came by way of Solderon (well I have to have something to occupy my time!) I'm not sure about these "modern day" pieces, prefer the metal and wood construction...and the micro-computer thing is also daunting, but they do look rather slick with the digital display.  


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Dillen
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Dillen replied on Thu, Jun 20 2019 8:40 PM

The screening is the same as in any other capacitor. The housing is alu all the way.
It's just the fitting with three grounding pins that is different, and (in this case) it's merely a matter of mounting stability.
Any good quality capacitor of the same value and rating will be fine, - just keep in mind to connect any and all of the used negative pin PCB-pads together, since
this connection is removed with the original capacitor.

2600uF is not OK for a 2200uF capacitor.
Popular speaking, you can look at an electrolytic capacitor as a natural rubber elastic band (think old fashion underwear).
When new and fresh, you can stretch it (charge it) and when you release it (discharge it), it will return to its original shape and size.
It will work like this for years, but eventually the elasticity degrades, and at some point you will be able to stretch the elastic, - perhaps even
beyond its original limit -, and it will just remain there and never go back.

It's a typical sign for aging capacitors to see their capacitance go up on capacitance meters, but when working in a circuit they really won't do a lot anymore.

Martin

Craig
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Craig replied on Thu, Jun 20 2019 8:45 PM

Martin

Thanks for clearing that up for me...I will link the can connections together as you say, always a school day in Beoworld ;¬)

Craig

Craig
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Power supply board finished and back in place....no issues.


Craig
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FM board next in line.....I will replace the trimmers one at a time on this board, testing everything after each one is changed out.....seem to remember being advised to do that one time ;¬)

 


Craig
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Finally got all the trimmers replaced....13 of them on this board, replaced them one at a time and re installed the board and carried out function tests to make sure I had set the correct positions on the replacements, not an ideal solution I know but without all the right equipment (and experience) its the next best thing, some of them are pretty straightforward as 2 legs are actually joined on the board so the correct resistance can be set quite accurately across the wiper and leg, some are not so easy and one does one best and then tests it out....seems I got lucky with those as everything sounds good to me.

Capacitors next...…..

 


chartz
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chartz replied on Tue, Jun 25 2019 4:28 PM

I never replace the tuner trimmers.

How do you adjust them?

Methinks you can’t just measure them, can you? 😕

Jacques

Søren Mexico
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chartz:
Methinks you can’t just measure them, can you? 😕

I do the same as Craig. take them out measure resistance and set the new ones to the same value.

Collecting Vintage B&O is not a hobby, its a lifestyle.

Craig
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I'm sure its not the best way to do it, but it seems to work for me.....I think its important to do one at a time and test the function of the tuner, that way if you get it wrong you only have one to adjust to pull it back into line....

However I now have another small issue going on, I have discovered that one of my existing capacitors is non polarised......8C71 (100uf). I don't think I can replace this with an electrolytic polarised component......


Craig
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Here is the circuit diagram showing said capacitor, are non polarised aluminium electrolytic caps available.....don't think I've seen any any....


sonavor
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The tuner part of a restoration is a touchy/tricky one.

The way I see it there are several options -

1. If it is still working then you could leave it alone. Without proper test equipment you are going by your own ears as to whether you think the FM tuning is as good as it can be.  Perhaps characteristics have changed with age...how would you know?

2. You could recap the tuner and leave the trimmers as they were originally set. Again though...did the new capacitors change anything that requires a recalibration. Are the trimmers actually good?

3. You can recap the tuner and replace all of the trimmers. You can take your chances with the result or execute the service manual adjustments to calibrate. Attempting to match the new trimmers with the values of the originals is still just a guess in my opinion. You don't really know if the original trimmer positions are still valid and with other new components the trimmer values should possibly be changed anyway. 

I figure that ideally the tuner would be updated and a fresh calibration be performed. That is difficult to do since most people won't have the necessary equipment and guidance (the service manual instructions are not the most verbose).  I haven't tried doing this but I have often thought it would be a good idea to reach out to an experienced radio enthusiast for help in calibrating the tuner. They are hard to find though. Maybe a Ham Radio enthusiast. They usually have a lot of RF equipment handy.

So the typical option is to do either option one, two or three and most of the time the FM tuner boards still continue to work decent enough to be acceptable. Depending on where you live you may not have high quality FM stations available where it makes a difference. 

sonavor

 

sonavor
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Craig:

Here is the circuit diagram showing said capacitor, are non polarised aluminium electrolytic caps available.....don't think I've seen any any....

 

Mouser carries a few.  

-sonavor

 

chartz
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chartz replied on Wed, Jun 26 2019 6:23 AM

I always choose option one.

I leave the tuner boards well alone because 99 times out of 100 they just carry on working fine and I don’t have the equipment, although I definitely contemplate getting it (DIY style).

Jacques

solderon29
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It's looking good Craig!

The tuner/if board is quite forgiving in my experience,and your method of setting the pot's is shrewd and effective,after all how can you mess up with setting like for like.You won't be far out as a worst case surely?

The bipolar cap is available from CPC No.CA05948.

I did venture out into the relatively uncharted territory of my B&O treasure trove,but I don't have one of those cap's at the mo.Must "get some in"!

I did find a spare tuner if board though!!!

When you get to the final stages of this project,you will probably wonder about the programming cover action?

Originally,the soft raise action, typical of B&O attention to detail,was achieved by attaching a rather clever damping mechanism to the cover.The mechanism relied on the sticking action of a special grease.We used to call it "beogoo",but I think it's proper name was Killapoise.

It leaks out over the years,and that explains the little sticky puddle you usually find in the bottom of the Beomaster's

I haven't come across any for years,praps other members here have some experience of this?

I wonder if you could use the goo employed in pu arm lowering damper's.

Keep up the good work sir!

Nick

 

Dillen
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Dillen replied on Wed, Jun 26 2019 11:31 AM

Is this a bad time to mention, that the three bipolar caps are included in the service kit, as are trimmers, lamps and all other board-mounted electrolytic caps...  Whistle

Kilopoise grease can be found on Ebay in small amounts. It's used for toilet-seat dampening etc.

Martin

Craig
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Craig replied on Wed, Jun 26 2019 12:28 PM

Martin.........serves me right!

And there are three off such capacitors?....havent come across the other two as yet, however if you could send me a paypal invoice for said capacitors and a set of lamps I would appreciate it ;¬)

As for the Kilopoise I will check out ebay....is it coincidence that the engineering unit of viscosity is centipoise, as this is a very sticky grease it seems likely there is a connection.

Craig

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