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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 20th Aug 2019, 3:02 pm   #1
record man
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Default Bang & olufsen 3300 type 1604 fuses

Afternoon, does anyone know where the internal fuses are and how to get to them. Also how do i set the voltage there does not seem to be a mark.
Many thanks

Last edited by record man; 20th Aug 2019 at 3:28 pm.
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Old 20th Aug 2019, 4:33 pm   #2
60 oldjohn
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Default Re: Bang & olufsen 3300 type 1604 fuses

Have you had a look under the set for the fuses? only a guess.


John.

PS please don't just turn it upside down to look. The platter should be removed, cover put over stylus, arm secured and lid made so it can not open. Take care not to damage the lid.

Last edited by 60 oldjohn; 20th Aug 2019 at 4:45 pm.
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Old 21st Aug 2019, 9:32 am   #3
Max Ripple
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Default Re: Bang & olufsen 3300 type 1604 fuses

What is your equipment?"3300" could be a receiver,tape recorder,record player or cd player,as these units were all part of Beosystem 3300.
I think that there was a Beocenter 3300 too?
Nick
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Old 21st Aug 2019, 10:14 am   #4
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Default Re: Bang & olufsen 3300 type 1604 fuses

If you don't know, don't guess... Its one of these:

https://beocentral.com/beocenter3300

The fuses are on the top. You need to remove the aluminium panel that forms the top of the cabinet, the screws for this are under the black trim that runs across the back.

This model uses a crowbar circuit and will blow the fuses automatically (violently...!) if there is an excessive DC offset on either power amplifier output. Crumbling red electrolytics are the usual cause, check them all in both power amplifier modules and the power supply regulator panel. Note that some of them are reversible types, ordinary ones won't do. In extreme cases the output transistors may also be faulty so check these too. Diagnosis is difficult due to the pegboard chassis so its best to run the meter over every transistor and diode in the output stage modules is you find a faulty output transistor.
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Old 21st Aug 2019, 4:25 pm   #5
Max Ripple
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Default Re: Bang & olufsen 3300 type 1604 fuses

Good luck with that then?
The aptly named crowbar protection system was so called as it mimicked the effect of dropping a crowbar (or similar implement!)across the supply lines,so blowing(and how!)the fuses.
Sadly the protection circuit had a habit of spontaneously combusting even without a fault being present,although I remember that B&O produced a mod kit to overcome(sometimes!) this malady.
Is there not a mains carousel adjuster somewhere on the unit,probably underneath?You might be lucky and the unit is set to 220(or less?) instead of 240v?
You'll still need to explore inside for the fuses though,and it's not for the faint hearted.

Not one of B&O's best efforts IMHO,and only redeemed by producing wonderful sound when working!
Nick
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Old 22nd Aug 2019, 9:50 am   #6
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Default Re: Bang & olufsen 3300 type 1604 fuses

Quote:
Originally Posted by Max Ripple View Post
Not one of B&O's best efforts IMHO
Nick
Really? This chassis was part of 'Project Tango', which produced the little Beomaster 1500 and the mighty Beomaster 4400 as well. The Beocenter 3300 is a derivative of the Beomaster 2200, which I've head described as the nicest sounding amplifier that B&O made. When in good condition its hard to disagree with that, but they are all 40 years old now so you need to do a fair amount of work to get them up to that standard.

The Beocenter 3300 was essentially a Beomaster 2200 with a shortened fascia combined with a Beogram 1902 turntable. They also made a Beocenter 4000 which was the same radio chassis and a condensed form of the Beocord 5000 cassette deck, using B&O's own mechanism. This was probably the most practical version of the rather over complex deck, it had a single capstan drive and a different reel motor arrangement which cured many (but not all) of the Beocord 5000's bad habits. Sadly they never made a version with both the cassette deck and the turntable, it would have been stunning.
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Old 22nd Aug 2019, 11:45 am   #7
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Default Re: Bang & olufsen 3300 type 1604 fuses

Crowbar circuits are useful for equipment intended for use in the USA to cope with a not uncommon fault mode of domestic electricity installations where the customer is supplied via a transformer with a centre-tapped 240V secondary providing two 120V circuits. If the centre tap goes open circuit, both 120V circuits care connected in series, OK if they are equally loaded, but for example a high wattage toaster on one in series with a low wattage radio on the other would put over 200V on the radio, hence the desirability of crowbar protection in their light current appliances. It's a solution to a problem that doesn't usually exist in Europe.
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Old 22nd Aug 2019, 2:05 pm   #8
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Default Re: Bang & olufsen 3300 type 1604 fuses

The crowbar circuit is necessary for loudspeaker protection. This was the second generation of high powered DC coupled amplifier from B&O (the original Beomaster 2000 being the first), before that they had all had big DC blocking capacitors between the output transistors and the loudspeaker load (Beomaster 3000, 3000 mk2, Beolab 5000 etc).

There are various ways to go about this. The British approach more often than not was just to let 'em burn, if an output transistor fails (quite likely in British gear...) it will more than likely take the woofer of the loudspeaker connected to it with it. It is possible to put a fuse in series, but its non-linear resistance offends the purists. The Japanese approach is to use an electronically controlled relay between the amplifier and the loudspeakers which works well when new, but since it spends most of its life switching on and off at essentially zero current the contacts tend to corrode and give erratic results after some years of use - this is always my first port of call when servicing any quality Japanese amplifier. The crowbar system gives effective protection without putting anything unnecessary in the signal path so it is satisfying at a technical level, however it is strictly a 'one shot' device which makes it a nuisance from a customer relations point of view.

The bigger Beomaster 4400 model had a relay, but it was in the DC power feed to the output stages rather than in the direct signal path. This appeared to be a good compromise; the amplifier's bias current helped to keep the contacts preened and its internal PSRR and NFB loop effectively counteracted any effect it may have of marginally increasing the supply impedance.

Because the 2200 chassis (as used in the Beocenter 3300) is modular one can remove the output modules if they are suspected of firing the crowbar. If the fuses then hold, they can be plugged back in one at a time to see which is faulty. To be fair though, its normally mouldy electrolytics on the power supply regulator panel that cause it to misfire.
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Old 22nd Aug 2019, 3:07 pm   #9
Max Ripple
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Default Re: Bang & olufsen 3300 type 1604 fuses

Well,we can agree on the sound quality of the Beomaster 2200/Beocenter 3300/4000 etc at least?
They must have been expensive to make with that awful wire wrapping and plug in modules.And they certainly were not reliable,not just the spontaneously combusting crowbar protection(no electrolytic cap problems while still under warranty!),but also with that terrible tape deck! The record deck was ok though!

They were also susceptable to rfi,which might with the benefit of hindsight have had a role in the aforementioned combustion scenario?

The Beomaster 1500 and '4400 were of course super sounding,but not without their particular foibles.
Not a happy period for B&O,as they tended to earn their "all dress and no knickers" reputation somewhat.
They moved on though with the sublime Beomaster 6000/8000,and the Beocenter 5000/7000/02(no crowbar's there!)and they haven't really looked back since?
Nick
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Old 23rd Aug 2019, 2:17 pm   #10
record man
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Default Re: Bang & olufsen 3300 type 1604 fuses

Many thanks all most informative, just one more niggle the brown switch covers how do i re attach them to the push on/off switch?
Steve
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