BANG & OLUFSEN BEOLIT DE LUXE 611 FME (tr36) - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Wrangler · 27th Apr 2023, 1:50 pm

The voltage difference between primary cells and NiMH can be a problem.

I bought a camera which takes 8x AA cells in a slide-in pack to give it 12v for metering, shutter and motor drive. Feeling clever I bought a load of good make NiMH cells and a charger. The camera could run off over a dozen films on one set of primary cells. It wouldn't manage a second film on the NiMH. In fact, if not charged that morning it would shut down before the first film could be rewound. It was relying on the surface charge voltage!

But Nikon did a slide in NiMH pack and a charger for same...£350 or thereaouts, ouch! When I later had saved up, I found that the ir pack had 9 NiMH cells in it to get above the shutoff point. The point is that some things are very fussy about batteryvoltage.

If the B&O set has had silicon transistors put in the output stage, then it will be more demanding on battery voltage for the same output power. The NiMH win in terms of less voltage droop for the same currents. Come to think of it, they can provide brutal currents. You may want to add a fuse as fire protection.

David

agardiner · 27th Apr 2023, 2:02 pm

Quote:

Originally Posted by Boulevardier

Quote:

Originally Posted by agardiner

I have a set of 6 C adapters loaded with Ni-Mh rechargeables, in use in one of my sets. Never had a problem.

I just wondered if running AA NiMHs in paralleled pairs (as seems to be done in the double-converters you linked to) could be problematic. I know that it's dodgy to charge them in parallel.
Mike

Personally I use the single cell options. Prevents any concern.

Remember that back in the day, Zinc was the main technology. So a good set of 2000mAH AA's will still run the set for ages.

Carlh93 · 29th Apr 2023, 3:42 pm

SECOND REPLY TO "RADIOMOBILE" - AND FAO ANYONE ELSE INTERESTED!

The Beolit FM611's moulded ABS(?) tuning pulley for the FM band capacitor (I assume it's not a pot?) is much larger than the metal one that you have available.

Its o/d is a strange size in mm: 31.74-ish. This may have been originally 31.75 (1.25"). The bore is fractionally under 6 mm (possibly 15/64" if imperial?)

The thickness, except at the hub on the inside* face, is 6.1 mm (it varies very slightly). The o/d of the hub is 14.90 mm.

The hub projects by a little under 1 mm and is moulded as a rectangular-section ring standing out from the inside (?) face with an i/d of just under 11mm. Filling the space inside this ring at one point, at a circumferential position marked with red paint on the original pulley (not so marked on the worse disintegrated one that you fitted in 2003), is a moulded-in locating key.

This key, which is 2.63 mm long, with a flat end coincident with the pulley's bore and is (obviously) the same depth as the hub ring, does not seem to have any function on the FM611, so perhaps it was originally produced for the earlier models?

There are no identification markings on the pulley. it is the same light grey as several other plastic parts, so may be one produced for this radio, and perhaps for some earlier and later versions of it also, and not a generic one.

There is a 1(I think)-start thread moulded into the thickness of the perimeter. It's a square threadform, a bit like an Acme screw thread, which is obviously because the pulley is turned by a cord

* Ashamed to say that am no longer sure which side of the pulley faces the capacitor! But I think that it is as stated above.

If, contrary to what I suspect, this tuning cord pulley was used on other brands of early portable FM radios, is there a matching pully which it may not be impossible to find in good original condition, or even remanufactured?

I realise that 3-D printing, using the better of the two original pulleys (the original one) as the pattern, may be a solution but I wonder if a replica accurate enough to do the job could really be produced by this method.

I would be delighted for my doubts on this to be shown to be groundless!

27th Apr 2023, 1:50 pm	#41
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,894	Re: BANG & OLUFSEN BEOLIT DE LUXE 611 FME (tr36) The voltage difference between primary cells and NiMH can be a problem. I bought a camera which takes 8x AA cells in a slide-in pack to give it 12v for metering, shutter and motor drive. Feeling clever I bought a load of good make NiMH cells and a charger. The camera could run off over a dozen films on one set of primary cells. It wouldn't manage a second film on the NiMH. In fact, if not charged that morning it would shut down before the first film could be rewound. It was relying on the surface charge voltage! But Nikon did a slide in NiMH pack and a charger for same...£350 or thereaouts, ouch! When I later had saved up, I found that the ir pack had 9 NiMH cells in it to get above the shutoff point. The point is that some things are very fussy about batteryvoltage. If the B&O set has had silicon transistors put in the output stage, then it will be more demanding on battery voltage for the same output power. The NiMH win in terms of less voltage droop for the same currents. Come to think of it, they can provide brutal currents. You may want to add a fuse as fire protection. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

29th Apr 2023, 3:42 pm	#43
Carlh93 Triode Join Date: Mar 2023 Location: Retford, Nottinghamshire, UK. Posts: 16	Re: BANG & OLUFSEN BEOLIT DE LUXE 611 FME (tr36) SECOND REPLY TO "RADIOMOBILE" - AND FAO ANYONE ELSE INTERESTED! The Beolit FM611's moulded ABS(?) tuning pulley for the FM band capacitor (I assume it's not a pot?) is much larger than the metal one that you have available. Its o/d is a strange size in mm: 31.74-ish. This may have been originally 31.75 (1.25"). The bore is fractionally under 6 mm (possibly 15/64" if imperial?) The thickness, except at the hub on the inside* face, is 6.1 mm (it varies very slightly). The o/d of the hub is 14.90 mm. The hub projects by a little under 1 mm and is moulded as a rectangular-section ring standing out from the inside (?) face with an i/d of just under 11mm. Filling the space inside this ring at one point, at a circumferential position marked with red paint on the original pulley (not so marked on the worse disintegrated one that you fitted in 2003), is a moulded-in locating key. This key, which is 2.63 mm long, with a flat end coincident with the pulley's bore and is (obviously) the same depth as the hub ring, does not seem to have any function on the FM611, so perhaps it was originally produced for the earlier models? There are no identification markings on the pulley. it is the same light grey as several other plastic parts, so may be one produced for this radio, and perhaps for some earlier and later versions of it also, and not a generic one. There is a 1(I think)-start thread moulded into the thickness of the perimeter. It's a square threadform, a bit like an Acme screw thread, which is obviously because the pulley is turned by a cord * Ashamed to say that am no longer sure which side of the pulley faces the capacitor! But I think that it is as stated above. If, contrary to what I suspect, this tuning cord pulley was used on other brands of early portable FM radios, is there a matching pully which it may not be impossible to find in good original condition, or even remanufactured? I realise that 3-D printing, using the better of the two original pulleys (the original one) as the pattern, may be a solution but I wonder if a replica accurate enough to do the job could really be produced by this method. I would be delighted for my doubts on this to be shown to be groundless!